modified scull code for 3.x.x

The scull code is the examples that the book, linux device drivers by Jonathan Corbet uses to explain the various concepts of character devices.

Here is the same code modified for 3.x.x kernel versions. The code has been tested in kernel version 3.7.5

main.c
access.c
pipe.c

Change the following line in scull.h

int scull_ioctl(struct inode *inode struct file *filp,unsigned int cmd, unsigned long arg); to long scull_ioctl(struct file *filp,unsigned int cmd, unsigned long arg);

pipe.c of ldd3 modified for 3.x.x kernel version

Here is the pipe.c code of scull, which is a part of Linux Device Drivers by Jonathan Corbet, modified for the kernel version 3.x.x. The code has been tested on 3.7.5 /* * pipe.c -- fifo driver for scull * * Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet * Copyright (C) 2001 O'Reilly & Associates * * The source code in this file can be freely used, adapted, * and redistributed in source or binary form, so long as an * acknowledgment appears in derived source files. The citation * should list that the code comes from the book "Linux Device * Drivers" by Alessandro Rubini and Jonathan Corbet, published * by O'Reilly & Associates. No warranty is attached; * we cannot take responsibility for errors or fitness for use. * */ #include <linux/module.h> #include <linux/moduleparam.h> #include <linux/kernel.h> /* printk(), min() */ #include <linux/slab.h> /* kmalloc() */ #include <linux/fs.h> /* everything... */ #include <linux/proc_fs.h> #include <linux/errno.h> /* error codes */ #include <linux/types.h> /* size_t */ #include <linux/fcntl.h> #include <linux/poll.h> #include <linux/cdev.h> #include <asm/uaccess.h> #include <linux/sched.h> #include "scull.h" /* local definitions */ struct scull_pipe { wait_queue_head_t inq, outq; /* read and write queues */ char *buffer, *end; /* begin of buf, end of buf */ int buffersize; /* used in pointer arithmetic */ char *rp, *wp; /* where to read, where to write */ int nreaders, nwriters; /* number of openings for r/w */ struct fasync_struct *async_queue; /* asynchronous readers */ struct semaphore sem; /* mutual exclusion semaphore */ struct cdev cdev; /* Char device structure */ }; /* parameters */ static int scull_p_nr_devs = SCULL_P_NR_DEVS; /* number of pipe devices */ int scull_p_buffer = SCULL_P_BUFFER; /* buffer size */ dev_t scull_p_devno; /* Our first device number */ module_param(scull_p_nr_devs, int, 0); /* FIXME check perms */ module_param(scull_p_buffer, int, 0); static struct scull_pipe *scull_p_devices; static int scull_p_fasync(int fd, struct file *filp, int mode); static int spacefree(struct scull_pipe *dev); /* * Open and close */ static int scull_p_open(struct inode *inode, struct file *filp) { struct scull_pipe *dev; dev = container_of(inode->i_cdev, struct scull_pipe, cdev); filp->private_data = dev; if (down_interruptible(&dev->sem)) return -ERESTARTSYS; if (!dev->buffer) { /* allocate the buffer */ dev->buffer = kmalloc(scull_p_buffer, GFP_KERNEL); if (!dev->buffer) { up(&dev->sem); return -ENOMEM; } } dev->buffersize = scull_p_buffer; dev->end = dev->buffer + dev->buffersize; dev->rp = dev->wp = dev->buffer; /* rd and wr from the beginning */ /* use f_mode,not f_flags: it's cleaner (fs/open.c tells why) */ if (filp->f_mode & FMODE_READ) dev->nreaders++; if (filp->f_mode & FMODE_WRITE) dev->nwriters++; up(&dev->sem); return nonseekable_open(inode, filp); } static int scull_p_release(struct inode *inode, struct file *filp) { struct scull_pipe *dev = filp->private_data; /* remove this filp from the asynchronously notified filp's */ scull_p_fasync(-1, filp, 0); down(&dev->sem); if (filp->f_mode & FMODE_READ) dev->nreaders--; if (filp->f_mode & FMODE_WRITE) dev->nwriters--; if (dev->nreaders + dev->nwriters == 0) { kfree(dev->buffer); dev->buffer = NULL; /* the other fields are not checked on open */ } up(&dev->sem); return 0; } /* * Data management: read and write */ static ssize_t scull_p_read (struct file *filp, char __user *buf, size_t count, loff_t *f_pos) { struct scull_pipe *dev = filp->private_data; if (down_interruptible(&dev->sem)) return -ERESTARTSYS; while (dev->rp == dev->wp) { /* nothing to read */ up(&dev->sem); /* release the lock */ if (filp->f_flags & O_NONBLOCK) return -EAGAIN; PDEBUG("\"%s\" reading: going to sleep\n", current->comm); if (wait_event_interruptible(dev->inq, (dev->rp != dev->wp))) return -ERESTARTSYS; /* signal: tell the fs layer to handle it */ /* otherwise loop, but first reacquire the lock */ if (down_interruptible(&dev->sem)) return -ERESTARTSYS; } /* ok, data is there, return something */ if (dev->wp > dev->rp) count = min(count, (size_t)(dev->wp - dev->rp)); else /* the write pointer has wrapped, return data up to dev->end */ count = min(count, (size_t)(dev->end - dev->rp)); if (copy_to_user(buf, dev->rp, count)) { up (&dev->sem); return -EFAULT; } dev->rp += count; if (dev->rp == dev->end) dev->rp = dev->buffer; /* wrapped */ up (&dev->sem); /* finally, awake any writers and return */ wake_up_interruptible(&dev->outq); PDEBUG("\"%s\" did read %li bytes\n",current->comm, (long)count); return count; } /* Wait for space for writing; caller must hold device semaphore. On * error the semaphore will be released before returning. */ static int scull_getwritespace(struct scull_pipe *dev, struct file *filp) { while (spacefree(dev) == 0) { /* full */ DEFINE_WAIT(wait); up(&dev->sem); if (filp->f_flags & O_NONBLOCK) return -EAGAIN; PDEBUG("\"%s\" writing: going to sleep\n",current->comm); prepare_to_wait(&dev->outq, &wait, TASK_INTERRUPTIBLE); if (spacefree(dev) == 0) schedule(); finish_wait(&dev->outq, &wait); if (signal_pending(current)) return -ERESTARTSYS; /* signal: tell the fs layer to handle it */ if (down_interruptible(&dev->sem)) return -ERESTARTSYS; } return 0; } /* How much space is free? */ static int spacefree(struct scull_pipe *dev) { if (dev->rp == dev->wp) return dev->buffersize - 1; return ((dev->rp + dev->buffersize - dev->wp) % dev->buffersize) - 1; } static ssize_t scull_p_write(struct file *filp, const char __user *buf, size_t count, loff_t *f_pos) { struct scull_pipe *dev = filp->private_data; int result; if (down_interruptible(&dev->sem)) return -ERESTARTSYS; /* Make sure there's space to write */ result = scull_getwritespace(dev, filp); if (result) return result; /* scull_getwritespace called up(&dev->sem) */ /* ok, space is there, accept something */ count = min(count, (size_t)spacefree(dev)); if (dev->wp >= dev->rp) count = min(count, (size_t)(dev->end - dev->wp)); /* to end-of-buf */ else /* the write pointer has wrapped, fill up to rp-1 */ count = min(count, (size_t)(dev->rp - dev->wp - 1)); PDEBUG("Going to accept %li bytes to %p from %p\n", (long)count, dev->wp, buf); if (copy_from_user(dev->wp, buf, count)) { up (&dev->sem); return -EFAULT; } dev->wp += count; if (dev->wp == dev->end) dev->wp = dev->buffer; /* wrapped */ up(&dev->sem); /* finally, awake any reader */ wake_up_interruptible(&dev->inq); /* blocked in read() and select() */ /* and signal asynchronous readers, explained late in chapter 5 */ if (dev->async_queue) kill_fasync(&dev->async_queue, SIGIO, POLL_IN); PDEBUG("\"%s\" did write %li bytes\n",current->comm, (long)count); return count; } static unsigned int scull_p_poll(struct file *filp, poll_table *wait) { struct scull_pipe *dev = filp->private_data; unsigned int mask = 0; /* * The buffer is circular; it is considered full * if "wp" is right behind "rp" and empty if the * two are equal. */ down(&dev->sem); poll_wait(filp, &dev->inq, wait); poll_wait(filp, &dev->outq, wait); if (dev->rp != dev->wp) mask |= POLLIN | POLLRDNORM; /* readable */ if (spacefree(dev)) mask |= POLLOUT | POLLWRNORM; /* writable */ up(&dev->sem); return mask; } static int scull_p_fasync(int fd, struct file *filp, int mode) { struct scull_pipe *dev = filp->private_data; return fasync_helper(fd, filp, mode, &dev->async_queue); } /* FIXME this should use seq_file */ #ifdef SCULL_DEBUG static void scullp_proc_offset(char *buf, char **start, off_t *offset, int *len) { if (*offset == 0) return; if (*offset >= *len) { /* Not there yet */ *offset -= *len; *len = 0; } else { /* We're into the interesting stuff now */ *start = buf + *offset; *offset = 0; } } static int scull_read_p_mem(char *buf, char **start, off_t offset, int count, int *eof, void *data) { int i, len; struct scull_pipe *p; #define LIMIT (PAGE_SIZE-200) /* don't print any more after this size */ *start = buf; len = sprintf(buf, "Default buffersize is %i\n", scull_p_buffer); for(i = 0; i<scull_p_nr_devs && len <= LIMIT; i++) { p = &scull_p_devices[i]; if (down_interruptible(&p->sem)) return -ERESTARTSYS; len += sprintf(buf+len, "\nDevice %i: %p\n", i, p); /* len += sprintf(buf+len, " Queues: %p %p\n", p->inq, p->outq);*/ len += sprintf(buf+len, " Buffer: %p to %p (%i bytes)\n", p->buffer, p->end, p->buffersize); len += sprintf(buf+len, " rp %p wp %p\n", p->rp, p->wp); len += sprintf(buf+len, " readers %i writers %i\n", p->nreaders, p->nwriters); up(&p->sem); scullp_proc_offset(buf, start, &offset, &len); } *eof = (len <= LIMIT); return len; } #endif /* * The file operations for the pipe device * (some are overlayed with bare scull) */ struct file_operations scull_pipe_fops = { .owner = THIS_MODULE, .llseek = no_llseek, .read = scull_p_read, .write = scull_p_write, .poll = scull_p_poll, .unlocked_ioctl = scull_ioctl, .open = scull_p_open, .release = scull_p_release, .fasync = scull_p_fasync, }; /* * Set up a cdev entry. */ static void scull_p_setup_cdev(struct scull_pipe *dev, int index) { int err, devno = scull_p_devno + index; cdev_init(&dev->cdev, &scull_pipe_fops); dev->cdev.owner = THIS_MODULE; err = cdev_add (&dev->cdev, devno, 1); /* Fail gracefully if need be */ if (err) printk(KERN_NOTICE "Error %d adding scullpipe%d", err, index); } /* * Initialize the pipe devs; return how many we did. */ int scull_p_init(dev_t firstdev) { int i, result; result = register_chrdev_region(firstdev, scull_p_nr_devs, "scullp"); if (result < 0) { printk(KERN_NOTICE "Unable to get scullp region, error %d\n", result); return 0; } scull_p_devno = firstdev; scull_p_devices = kmalloc(scull_p_nr_devs * sizeof(struct scull_pipe), GFP_KERNEL); if (scull_p_devices == NULL) { unregister_chrdev_region(firstdev, scull_p_nr_devs); return 0; } memset(scull_p_devices, 0, scull_p_nr_devs * sizeof(struct scull_pipe)); for (i = 0; i < scull_p_nr_devs; i++) { init_waitqueue_head(&(scull_p_devices[i].inq)); init_waitqueue_head(&(scull_p_devices[i].outq)); sema_init(&scull_p_devices[i].sem,1); scull_p_setup_cdev(scull_p_devices + i, i); } #ifdef SCULL_DEBUG create_proc_read_entry("scullpipe", 0, NULL, scull_read_p_mem, NULL); #endif return scull_p_nr_devs; } /* * This is called by cleanup_module or on failure. * It is required to never fail, even if nothing was initialized first */ void scull_p_cleanup(void) { int i; #ifdef SCULL_DEBUG remove_proc_entry("scullpipe", NULL); #endif if (!scull_p_devices) return; /* nothing else to release */ for (i = 0; i < scull_p_nr_devs; i++) { cdev_del(&scull_p_devices[i].cdev); kfree(scull_p_devices[i].buffer); } kfree(scull_p_devices); unregister_chrdev_region(scull_p_devno, scull_p_nr_devs); scull_p_devices = NULL; /* pedantic */ }

access.c of ldd3 modified for 3.x.x kernel version

Here is the access.c code of scull, which is a part of Linux Device Drivers by Jonathan Corbet, modified for the kernel version 3.x.x. The code has been tested on 3.7.5 /* * access.c -- the files with access control on open * * Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet * Copyright (C) 2001 O'Reilly & Associates * * The source code in this file can be freely used, adapted, * and redistributed in source or binary form, so long as an * acknowledgment appears in derived source files. The citation * should list that the code comes from the book "Linux Device * Drivers" by Alessandro Rubini and Jonathan Corbet, published * by O'Reilly & Associates. No warranty is attached; * we cannot take responsibility for errors or fitness for use. * * $Id: access.c,v 1.17 2004/09/26 07:29:56 gregkh Exp $ */ /* FIXME: cloned devices as a use for kobjects? */ #include <linux/kernel.h> /* printk() */ #include <linux/module.h> #include <linux/slab.h> /* kmalloc() */ #include <linux/fs.h> /* everything... */ #include <linux/errno.h> /* error codes */ #include <linux/types.h> /* size_t */ #include <linux/fcntl.h> #include <linux/cdev.h> #include <linux/tty.h> #include <asm/atomic.h> #include <linux/list.h> #include <linux/sched.h> #include "scull.h" /* local definitions */ static dev_t scull_a_firstdev; /* Where our range begins */ /* * These devices fall back on the main scull operations. They only * differ in the implementation of open() and close() */ /************************************************************************ * * The first device is the single-open one, * it has an hw structure and an open count */ static struct scull_dev scull_s_device; static atomic_t scull_s_available = ATOMIC_INIT(1); static int scull_s_open(struct inode *inode, struct file *filp) { struct scull_dev *dev = &scull_s_device; /* device information */ if (! atomic_dec_and_test (&scull_s_available)) { atomic_inc(&scull_s_available); return -EBUSY; /* already open */ } /* then, everything else is copied from the bare scull device */ if ( (filp->f_flags & O_ACCMODE) == O_WRONLY) scull_trim(dev); filp->private_data = dev; return 0; /* success */ } static int scull_s_release(struct inode *inode, struct file *filp) { atomic_inc(&scull_s_available); /* release the device */ return 0; } /* * The other operations for the single-open device come from the bare device */ struct file_operations scull_sngl_fops = { .owner = THIS_MODULE, .llseek = scull_llseek, .read = scull_read, .write = scull_write, .unlocked_ioctl = scull_ioctl, .open = scull_s_open, .release = scull_s_release, }; /************************************************************************ * * Next, the "uid" device. It can be opened multiple times by the * same user, but access is denied to other users if the device is open */ static struct scull_dev scull_u_device; static int scull_u_count; /* initialized to 0 by default */ static uid_t scull_u_owner; /* initialized to 0 by default */ static spinlock_t scull_u_lock; static int scull_u_open(struct inode *inode, struct file *filp) { struct scull_dev *dev = &scull_u_device; /* device information */ spin_lock(&scull_u_lock); printk(KERN_INFO "%d",current_uid()); if (scull_u_count && (scull_u_owner != current_uid()) && /* allow user */ (scull_u_owner != current_euid()) && /* allow whoever did su */ !capable(CAP_DAC_OVERRIDE)) { /* still allow root */ spin_unlock(&scull_u_lock); return -EBUSY; /* -EPERM would confuse the user */ } if (scull_u_count == 0) scull_u_owner = current_uid(); /* grab it */ scull_u_count++; spin_unlock(&scull_u_lock); /* then, everything else is copied from the bare scull device */ if ((filp->f_flags & O_ACCMODE) == O_WRONLY) scull_trim(dev); filp->private_data = dev; return 0; /* success */ } static int scull_u_release(struct inode *inode, struct file *filp) { spin_lock(&scull_u_lock); scull_u_count--; /* nothing else */ spin_unlock(&scull_u_lock); return 0; } /* * The other operations for the device come from the bare device */ struct file_operations scull_user_fops = { .owner = THIS_MODULE, .llseek = scull_llseek, .read = scull_read, .write = scull_write, .unlocked_ioctl = scull_ioctl, .open = scull_u_open, .release = scull_u_release, }; /************************************************************************ * * Next, the device with blocking-open based on uid */ static struct scull_dev scull_w_device; static int scull_w_count; /* initialized to 0 by default */ static uid_t scull_w_owner; /* initialized to 0 by default */ static DECLARE_WAIT_QUEUE_HEAD(scull_w_wait); static spinlock_t scull_w_lock;// = SPIN_LOCK_UNLOCKED; static inline int scull_w_available(void) { return scull_w_count == 0 || scull_w_owner == current_uid() || scull_w_owner == current_euid() || capable(CAP_DAC_OVERRIDE); } static int scull_w_open(struct inode *inode, struct file *filp) { struct scull_dev *dev = &scull_w_device; /* device information */ spin_lock(&scull_w_lock); while (! scull_w_available()) { spin_unlock(&scull_w_lock); if (filp->f_flags & O_NONBLOCK) return -EAGAIN; if (wait_event_interruptible (scull_w_wait, scull_w_available())) return -ERESTARTSYS; /* tell the fs layer to handle it */ spin_lock(&scull_w_lock); } if (scull_w_count == 0) scull_w_owner = current_uid(); /* grab it */ scull_w_count++; spin_unlock(&scull_w_lock); /* then, everything else is copied from the bare scull device */ if ((filp->f_flags & O_ACCMODE) == O_WRONLY) scull_trim(dev); filp->private_data = dev; return 0; /* success */ } static int scull_w_release(struct inode *inode, struct file *filp) { int temp; spin_lock(&scull_w_lock); scull_w_count--; temp = scull_w_count; spin_unlock(&scull_w_lock); if (temp == 0) wake_up_interruptible_sync(&scull_w_wait); /* awake other uid's */ return 0; } /* * The other operations for the device come from the bare device */ struct file_operations scull_wusr_fops = { .owner = THIS_MODULE, .llseek = scull_llseek, .read = scull_read, .write = scull_write, .unlocked_ioctl = scull_ioctl, .open = scull_w_open, .release = scull_w_release, }; /************************************************************************ * * Finally the `cloned' private device. This is trickier because it * involves list management, and dynamic allocation. */ /* The clone-specific data structure includes a key field */ struct scull_listitem { struct scull_dev device; dev_t key; struct list_head list; }; /* The list of devices, and a lock to protect it */ static LIST_HEAD(scull_c_list); static spinlock_t scull_c_lock;// = SPIN_LOCK_UNLOCKED; /* A placeholder scull_dev which really just holds the cdev stuff. */ static struct scull_dev scull_c_device; /* Look for a device or create one if missing */ static struct scull_dev *scull_c_lookfor_device(dev_t key) { struct scull_listitem *lptr; list_for_each_entry(lptr, &scull_c_list, list) { if (lptr->key == key) return &(lptr->device); } /* not found */ lptr = kmalloc(sizeof(struct scull_listitem), GFP_KERNEL); if (!lptr) return NULL; /* initialize the device */ memset(lptr, 0, sizeof(struct scull_listitem)); lptr->key = key; scull_trim(&(lptr->device)); /* initialize it */ sema_init(&lptr->device.sem,1); /* place it in the list */ list_add(&lptr->list, &scull_c_list); return &(lptr->device); } static int scull_c_open(struct inode *inode, struct file *filp) { struct scull_dev *dev; dev_t key; if (!current->signal->tty) { PDEBUG("Process \"%s\" has no ctl tty\n", current->comm); return -EINVAL; } key = tty_devnum(current->signal->tty); /* look for a scullc device in the list */ spin_lock(&scull_c_lock); dev = scull_c_lookfor_device(key); spin_unlock(&scull_c_lock); if (!dev) return -ENOMEM; /* then, everything else is copied from the bare scull device */ if ( (filp->f_flags & O_ACCMODE) == O_WRONLY) scull_trim(dev); filp->private_data = dev; return 0; /* success */ } static int scull_c_release(struct inode *inode, struct file *filp) { /* * Nothing to do, because the device is persistent. * A `real' cloned device should be freed on last close */ return 0; } /* * The other operations for the device come from the bare device */ struct file_operations scull_priv_fops = { .owner = THIS_MODULE, .llseek = scull_llseek, .read = scull_read, .write = scull_write, .unlocked_ioctl = scull_ioctl, .open = scull_c_open, .release = scull_c_release, }; /************************************************************************ * * And the init and cleanup functions come last */ static struct scull_adev_info { char *name; struct scull_dev *sculldev; struct file_operations *fops; } scull_access_devs[] = { { "scullsingle", &scull_s_device, &scull_sngl_fops }, { "sculluid", &scull_u_device, &scull_user_fops }, { "scullwuid", &scull_w_device, &scull_wusr_fops }, { "sullpriv", &scull_c_device, &scull_priv_fops } }; #define SCULL_N_ADEVS 4 /* * Set up a single device. */ static void scull_access_setup (dev_t devno, struct scull_adev_info *devinfo) { struct scull_dev *dev = devinfo->sculldev; int err; /* Initialize the device structure */ dev->quantum = scull_quantum; dev->qset = scull_qset; sema_init(&dev->sem,1); /* Do the cdev stuff. */ cdev_init(&dev->cdev, devinfo->fops); kobject_set_name(&dev->cdev.kobj, devinfo->name); dev->cdev.owner = THIS_MODULE; err = cdev_add (&dev->cdev, devno, 1); /* Fail gracefully if need be */ if (err) { printk(KERN_NOTICE "Error %d adding %s\n", err, devinfo->name); kobject_put(&dev->cdev.kobj); } else printk(KERN_NOTICE "%s registered at %x\n", devinfo->name, devno); } int scull_access_init(dev_t firstdev) { int result, i; /* Get our number space */ result = register_chrdev_region (firstdev, SCULL_N_ADEVS, "sculla"); if (result < 0) { printk(KERN_WARNING "sculla: device number registration failed\n"); return 0; } scull_a_firstdev = firstdev; /* Set up each device. */ for (i = 0; i < SCULL_N_ADEVS; i++) scull_access_setup (firstdev + i, scull_access_devs + i); return SCULL_N_ADEVS; } /* * This is called by cleanup_module or on failure. * It is required to never fail, even if nothing was initialized first */ void scull_access_cleanup(void) { struct scull_listitem *lptr, *next; int i; /* Clean up the static devs */ for (i = 0; i < SCULL_N_ADEVS; i++) { struct scull_dev *dev = scull_access_devs[i].sculldev; cdev_del(&dev->cdev); scull_trim(scull_access_devs[i].sculldev); } /* And all the cloned devices */ list_for_each_entry_safe(lptr, next, &scull_c_list, list) { list_del(&lptr->list); scull_trim(&(lptr->device)); kfree(lptr); } /* Free up our number space */ unregister_chrdev_region(scull_a_firstdev, SCULL_N_ADEVS); return; }

main.c of ldd3 modified for 3.x.x kernel version

Here is the main.c code of scull, which is a part of Linux Device Drivers by Jonathan Corbet, modified for the kernel version 3.x.x. The code has been tested on 3.7.5 /* * main.c -- the bare scull char module * * Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet * Copyright (C) 2001 O'Reilly & Associates * * The source code in this file can be freely used, adapted, * and redistributed in source or binary form, so long as an * acknowledgment appears in derived source files. The citation * should list that the code comes from the book "Linux Device * Drivers" by Alessandro Rubini and Jonathan Corbet, published * by O'Reilly & Associates. No warranty is attached; * we cannot take responsibility for errors or fitness for use. * */ #include <linux/module.h> #include <linux/moduleparam.h> #include <linux/init.h> #include <linux/kernel.h> /* printk() */ #include <linux/slab.h> /* kmalloc() */ #include <linux/fs.h> /* everything... */ #include <linux/errno.h> /* error codes */ #include <linux/types.h> /* size_t */ #include <linux/proc_fs.h> #include <linux/fcntl.h> /* O_ACCMODE */ #include <linux/seq_file.h> #include <linux/cdev.h> #include <asm/uaccess.h> /* copy_*_user */ #include "scull.h" /* local definitions */ #define SUCLL_DEBUG 1 /* * Our parameters which can be set at load time. */ int scull_major = SCULL_MAJOR; int scull_minor = 0; int scull_nr_devs = SCULL_NR_DEVS; /* number of bare scull devices */ int scull_quantum = SCULL_QUANTUM; int scull_qset = SCULL_QSET; module_param(scull_major, int, S_IRUGO); module_param(scull_minor, int, S_IRUGO); module_param(scull_nr_devs, int, S_IRUGO); module_param(scull_quantum, int, S_IRUGO); module_param(scull_qset, int, S_IRUGO); MODULE_AUTHOR("Alessandro Rubini, Jonathan Corbet"); MODULE_LICENSE("Dual BSD/GPL"); struct scull_dev *scull_devices; /* allocated in scull_init_module */ /* * Empty out the scull device; must be called with the device * semaphore held. */ int scull_trim(struct scull_dev *dev) { struct scull_qset *next, *dptr; int qset = dev->qset; /* "dev" is not-null */ int i; for (dptr = dev->data; dptr; dptr = next) { /* all the list items */ if (dptr->data) { for (i = 0; i < qset; i++) kfree(dptr->data[i]); kfree(dptr->data); dptr->data = NULL; } next = dptr->next; kfree(dptr); } dev->size = 0; dev->quantum = scull_quantum; dev->qset = scull_qset; dev->data = NULL; return 0; } #ifdef SCULL_DEBUG /* use proc only if debugging */ /* * The proc filesystem: function to read and entry */ int scull_read_procmem(char *buf, char **start, off_t offset, int count, int *eof, void *data) { int i, j, len = 0; int limit = count - 80; /* Don't print more than this */ char *info; struct scull_dev *pr=&scull_devices[0]; struct scull_qset *prd = pr->data; for (i = 0; i < scull_nr_devs && len <= limit; i++) { struct scull_dev *d = &scull_devices[i]; struct scull_qset *qs = d->data; if (down_interruptible(&d->sem)) return -ERESTARTSYS; len += sprintf(buf+len,"\nDevice %i: qset %i, q %i, sz %li\n", i, d->qset, d->quantum, d->size); info = prd->data[0]; printk(KERN_INFO "in proc %s",info); for (; qs && len <= limit; qs = qs->next) { /* scan the list */ len += sprintf(buf + len, " item at %p, qset at %p\n", qs, qs->data); if (qs->data && !qs->next) /* dump only the last item */ for (j = 0; j < d->qset; j++) { if (qs->data[j]) len += sprintf(buf + len, " % 4i: %8p\n", j, qs->data[j]); } } up(&scull_devices[i].sem); } *eof = 1; return len; } /* * For now, the seq_file implementation will exist in parallel. The * older read_procmem function should maybe go away, though. */ /* * Here are our sequence iteration methods. Our "position" is * simply the device number. */ static void *scull_seq_start(struct seq_file *s, loff_t *pos) { if (*pos >= scull_nr_devs) return NULL; /* No more to read */ return scull_devices + *pos; } static void *scull_seq_next(struct seq_file *s, void *v, loff_t *pos) { (*pos)++; if (*pos >= scull_nr_devs) return NULL; return scull_devices + *pos; } static void scull_seq_stop(struct seq_file *s, void *v) { /* Actually, there's nothing to do here */ } static int scull_seq_show(struct seq_file *s, void *v) { struct scull_dev *dev = (struct scull_dev *) v; struct scull_qset *d; int i; if (down_interruptible(&dev->sem)) return -ERESTARTSYS; seq_printf(s, "\nDevice %i: qset %i, q %i, sz %li\n", (int) (dev - scull_devices), dev->qset, dev->quantum, dev->size); for (d = dev->data; d; d = d->next) { /* scan the list */ seq_printf(s, " item at %p, qset at %p\n", d, d->data); if (d->data && !d->next) /* dump only the last item */ for (i = 0; i < dev->qset; i++) { if (d->data[i]) seq_printf(s, " % 4i: %8p\n", i, d->data[i]); } } up(&dev->sem); return 0; } /* * Tie the sequence operators up. */ static struct seq_operations scull_seq_ops = { .start = scull_seq_start, .next = scull_seq_next, .stop = scull_seq_stop, .show = scull_seq_show }; /* * Now to implement the /proc file we need only make an open * method which sets up the sequence operators. */ static int scull_proc_open(struct inode *inode, struct file *file) { return seq_open(file, &scull_seq_ops); } /* * Create a set of file operations for our proc file. */ static struct file_operations scull_proc_ops = { .owner = THIS_MODULE, .open = scull_proc_open, .read = seq_read, .llseek = seq_lseek, .release = seq_release }; /* * Actually create (and remove) the /proc file(s). */ static void scull_create_proc(void) { struct proc_dir_entry *entry; create_proc_read_entry("scullmem", 0 /* default mode */, NULL /* parent dir */, scull_read_procmem, NULL /* client data */); entry = create_proc_entry("scullseq", 0, NULL); if (entry) entry->proc_fops = &scull_proc_ops; } static void scull_remove_proc(void) { /* no problem if it was not registered */ remove_proc_entry("scullmem", NULL /* parent dir */); remove_proc_entry("scullseq", NULL); } #endif /* SCULL_DEBUG */ /* * Open and close */ int scull_open(struct inode *inode, struct file *filp) { struct scull_dev *dev; /* device information */ dev = container_of(inode->i_cdev, struct scull_dev, cdev); filp->private_data = dev; /* for other methods */ /* now trim to 0 the length of the device if open was write-only */ if ( (filp->f_flags & O_ACCMODE) == O_WRONLY) { if (down_interruptible(&dev->sem)) return -ERESTARTSYS; scull_trim(dev); /* ignore errors */ up(&dev->sem); } return 0; /* success */ } int scull_release(struct inode *inode, struct file *filp) { return 0; } /* * Follow the list */ struct scull_qset *scull_follow(struct scull_dev *dev, int n) { struct scull_qset *qs = dev->data; /* Allocate first qset explicitly if need be */ if (! qs) { qs = dev->data = kmalloc(sizeof(struct scull_qset), GFP_KERNEL); if (qs == NULL) return NULL; /* Never mind */ memset(qs, 0, sizeof(struct scull_qset)); } /* Then follow the list */ while (n--) { if (!qs->next) { qs->next = kmalloc(sizeof(struct scull_qset), GFP_KERNEL); if (qs->next == NULL) return NULL; /* Never mind */ memset(qs->next, 0, sizeof(struct scull_qset)); } qs = qs->next; continue; } return qs; } /* * Data management: read and write */ ssize_t scull_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos) { struct scull_dev *dev = filp->private_data; struct scull_qset *dptr; /* the first listitem */ int quantum = dev->quantum, qset = dev->qset; int itemsize = quantum * qset; /* how many bytes in the listitem */ int item, s_pos, q_pos, rest; ssize_t retval = 0; if (down_interruptible(&dev->sem)) return -ERESTARTSYS; if (*f_pos >= dev->size) goto out; if (*f_pos + count > dev->size) count = dev->size - *f_pos; /* find listitem, qset index, and offset in the quantum */ item = (long)*f_pos / itemsize; rest = (long)*f_pos % itemsize; s_pos = rest / quantum; q_pos = rest % quantum; /* follow the list up to the right position (defined elsewhere) */ dptr = scull_follow(dev, item); if (dptr == NULL || !dptr->data || ! dptr->data[s_pos]) goto out; /* don't fill holes */ /* read only up to the end of this quantum */ if (count > quantum - q_pos) count = quantum - q_pos; if (copy_to_user(buf, dptr->data[s_pos] + q_pos, count)) { retval = -EFAULT; goto out; } *f_pos += count; retval = count; out: printk(KERN_INFO "ret = %d",retval); up(&dev->sem); return retval; } ssize_t scull_write(struct file *filp, const char __user *buf, size_t count, loff_t *f_pos) { struct scull_dev *dev = filp->private_data; struct scull_qset *dptr; int quantum = dev->quantum, qset = dev->qset; int itemsize = quantum * qset; int item, s_pos, q_pos, rest; ssize_t retval = -ENOMEM; /* value used in "goto out" statements */ if (down_interruptible(&dev->sem)) return -ERESTARTSYS; /* find listitem, qset index and offset in the quantum */ item = (long)*f_pos / itemsize; rest = (long)*f_pos % itemsize; s_pos = rest / quantum; q_pos = rest % quantum; /* follow the list up to the right position */ dptr = scull_follow(dev, item); if (dptr == NULL) goto out; if (!dptr->data) { dptr->data = kmalloc(qset * sizeof(char *), GFP_KERNEL); if (!dptr->data) goto out; memset(dptr->data, 0, qset * sizeof(char *)); } if (!dptr->data[s_pos]) { dptr->data[s_pos] = kmalloc(quantum, GFP_KERNEL); if (!dptr->data[s_pos]) goto out; } /* write only up to the end of this quantum */ if (count > quantum - q_pos) count = quantum - q_pos; if (copy_from_user(dptr->data[s_pos]+q_pos, buf, count)) { retval = -EFAULT; goto out; } *f_pos += count; retval = count; /* update the size */ if (dev->size < *f_pos) dev->size = *f_pos; printk(KERN_INFO "ret = %d",retval); out: up(&dev->sem); return retval; } /* * The ioctl() implementation */ long scull_ioctl(struct file *filp,unsigned int cmd, unsigned long arg) { int err = 0, tmp; int retval = 0; struct scull_dev *sr=&scull_devices[0]; struct scull_qset *srd=sr->data; char *info; /* * extract the type and number bitfields, and don't decode * wrong cmds: return ENOTTY (inappropriate ioctl) before access_ok() */ if (_IOC_TYPE(cmd) != SCULL_IOC_MAGIC) return -ENOTTY; if (_IOC_NR(cmd) > SCULL_IOC_MAXNR) return -ENOTTY; /* * the direction is a bitmask, and VERIFY_WRITE catches R/W * transfers. `Type' is user-oriented, while * access_ok is kernel-oriented, so the concept of "read" and * "write" is reversed */ if (_IOC_DIR(cmd) & _IOC_READ) err = !access_ok(VERIFY_WRITE, (void __user *)arg, _IOC_SIZE(cmd)); else if (_IOC_DIR(cmd) & _IOC_WRITE) err = !access_ok(VERIFY_READ, (void __user *)arg, _IOC_SIZE(cmd)); if (err) return -EFAULT; switch(cmd) { case SCULL_IOCRESET: scull_quantum = SCULL_QUANTUM; scull_qset = SCULL_QSET; break; case SCULL_IOCSQUANTUM: /* Set: arg points to the value */ if (! capable (CAP_SYS_ADMIN)) return -EPERM; retval = __get_user(scull_quantum, (int __user *)arg); break; case SCULL_IOCTQUANTUM: /* Tell: arg is the value */ if (! capable (CAP_SYS_ADMIN)) return -EPERM; scull_quantum = arg; break; case SCULL_IOCGQUANTUM: /* Get: arg is pointer to result */ retval = __put_user(scull_quantum, (int __user *)arg); break; case SCULL_IOCQQUANTUM: /* Query: return it (it's positive) */ return scull_quantum; case SCULL_IOCXQUANTUM: /* eXchange: use arg as pointer */ if (! capable (CAP_SYS_ADMIN)) return -EPERM; tmp = scull_quantum; retval = __get_user(scull_quantum, (int __user *)arg); if (retval == 0) retval = __put_user(tmp, (int __user *)arg); break; case SCULL_IOCHQUANTUM: /* sHift: like Tell + Query */ if (! capable (CAP_SYS_ADMIN)) return -EPERM; tmp = scull_quantum; scull_quantum = arg; return tmp; case SCULL_IOCSQSET: if (! capable (CAP_SYS_ADMIN)) return -EPERM; retval = __get_user(scull_qset, (int __user *)arg); break; case SCULL_IOCTQSET: if (! capable (CAP_SYS_ADMIN)) return -EPERM; scull_qset = arg; break; case SCULL_IOCGQSET: retval = __put_user(scull_qset, (int __user *)arg); break; case SCULL_IOCQQSET: return scull_qset; case SCULL_IOCXQSET: if (! capable (CAP_SYS_ADMIN)) return -EPERM; tmp = scull_qset; retval = __get_user(scull_qset, (int __user *)arg); if (retval == 0) retval = put_user(tmp, (int __user *)arg); break; case SCULL_IOCHQSET: if (! capable (CAP_SYS_ADMIN)) return -EPERM; tmp = scull_qset; scull_qset = arg; return tmp; /* * The following two change the buffer size for scullpipe. * The scullpipe device uses this same ioctl method, just to * write less code. Actually, it's the same driver, isn't it? */ case SCULL_P_IOCTSIZE: scull_p_buffer = arg; break; case SCULL_P_IOCQSIZE: return scull_p_buffer; break; case SCULL_SORT: printk(KERN_INFO "entering sort"); retval = __get_user(tmp,(int __user *)arg); info = srd->data[tmp]; printk(KERN_INFO "in case %s",info); break; default: /* redundant, as cmd was checked against MAXNR */ return -ENOTTY; } return retval; } /* * The "extended" operations -- only seek */ loff_t scull_llseek(struct file *filp, loff_t off, int whence) { struct scull_dev *dev = filp->private_data; loff_t newpos; switch(whence) { case 0: /* SEEK_SET */ newpos = off; break; case 1: /* SEEK_CUR */ newpos = filp->f_pos + off; break; case 2: /* SEEK_END */ newpos = dev->size + off; break; default: /* can't happen */ return -EINVAL; } if (newpos < 0) return -EINVAL; filp->f_pos = newpos; return newpos; } struct file_operations scull_fops = { .owner = THIS_MODULE, .llseek = scull_llseek, .read = scull_read, .write = scull_write, .unlocked_ioctl = scull_ioctl, .open = scull_open, .release = scull_release, }; /* * Finally, the module stuff */ /* * The cleanup function is used to handle initialization failures as well. * Thefore, it must be careful to work correctly even if some of the items * have not been initialized */ void scull_cleanup_module(void) { int i; dev_t devno = MKDEV(scull_major, scull_minor); /* Get rid of our char dev entries */ if (scull_devices) { for (i = 0; i < scull_nr_devs; i++) { scull_trim(scull_devices + i); cdev_del(&scull_devices[i].cdev); } kfree(scull_devices); } #ifdef SCULL_DEBUG /* use proc only if debugging */ scull_remove_proc(); #endif /* cleanup_module is never called if registering failed */ unregister_chrdev_region(devno, scull_nr_devs); /* and call the cleanup functions for friend devices */ scull_p_cleanup(); scull_access_cleanup(); } /* * Set up the char_dev structure for this device. */ static void scull_setup_cdev(struct scull_dev *dev, int index) { int err, devno = MKDEV(scull_major, scull_minor + index); cdev_init(&dev->cdev, &scull_fops); dev->cdev.owner = THIS_MODULE; dev->cdev.ops = &scull_fops; err = cdev_add (&dev->cdev, devno, 1); /* Fail gracefully if need be */ if (err) printk(KERN_NOTICE "Error %d adding scull%d", err, index); } int scull_init_module(void) { int result, i; dev_t dev = 0; /* * Get a range of minor numbers to work with, asking for a dynamic * major unless directed otherwise at load time. */ if (scull_major) { dev = MKDEV(scull_major, scull_minor); result = register_chrdev_region(dev, scull_nr_devs, "scull"); } else { result = alloc_chrdev_region(&dev, scull_minor, scull_nr_devs, "scull"); scull_major = MAJOR(dev); } if (result < 0) { printk(KERN_WARNING "scull: can't get major %d\n", scull_major); return result; } /* * allocate the devices -- we can't have them static, as the number * can be specified at load time */ scull_devices = kmalloc(scull_nr_devs * sizeof(struct scull_dev), GFP_KERNEL); if (!scull_devices) { result = -ENOMEM; goto fail; /* Make this more graceful */ } memset(scull_devices, 0, scull_nr_devs * sizeof(struct scull_dev)); /* Initialize each device. */ for (i = 0; i < scull_nr_devs; i++) { scull_devices[i].quantum = scull_quantum; scull_devices[i].qset = scull_qset; sema_init(&scull_devices[i].sem,1); scull_setup_cdev(&scull_devices[i], i); } /* At this point call the init function for any friend device */ dev = MKDEV(scull_major, scull_minor + scull_nr_devs); dev += scull_p_init(dev); dev += scull_access_init(dev); #ifdef SCULL_DEBUG /* only when debugging */ scull_create_proc(); #endif return 0; /* succeed */ fail: scull_cleanup_module(); return result; } module_init(scull_init_module); module_exit(scull_cleanup_module);

Creating fire animation using gimp in linux

Here are the steps to create an animation, using gimp, as if an image is on fire as shown below.

To be able to create the animation we will need gimp along with the additional gimp packages, i.e. gimp animation packages gimp-gap and gimp-plugin-registry . To install these extra packages in debian based systems run the command

sudo apt-get install gimp-gap sudo apt-get install gimp-plugin-registry

Note: In the post we will add the fire effect to the image of a logo the same can be done to any other image.

Once the installation is successful, launch gimp and go to

file->create->logos->BasicII



Type the text for which the fire animation has to be added, we have used the text Fire. Choose any color of your preference.



We should see a window as below.



Now click on one of layers to which the animation has to be added and go to

Fx-Foundry->animaton->Fire animaton



In the menu that is shown we can choose



How many frames of fire animation has to be added, more the number of frames more detailed the fire will look

Overlap flames: How many frames of fire flames will overlap with each other.

Gradient: The color of the flames

Framerate: How fast should the flames appear, smaller the number faster the flames will appear

Angle: The angle of the flames

Distance: How high should the flames be, bigger the number higher the flames, hence the fire appears bigger.

Background: The image on which the flames should appear.

Now click OK and wait for gimp to do its magic. Once done, we should see a new window as below.



To see the animaton in a preview click on filter->animation->playback



Click on the play icon to see the animation.



If it is satisfactory then close the preview and save the animation by clicking

file->save as



Enter a file name with .gif as extension and from the file type options at the right bottom choose .gif and click on save.



A prompt will be shown confirming whether we need to save the file as animation or single image, select save as animation and click on "Export"



In the next window we can choose whether the animation should run once or continously by checking the loop forever box.We can also specify the delay between frames in case it is not mentioned in the layer attributes.



Now click on save. The fire animated image should be ready to use.

using read write lock in pthreads

When sharing resources between multiple threads, it is safe to allow multiple readers to access the resource simultaneous as they would not alter any data but only one writer should be allowed to access the resource at any given time.

The standard mutex, pthread_mutex_t, allows only one process to access the resource irrespective of whether the process is a reader or writer. The behavior even though safe, is not efficient, as the readers are made to wait even though they are not going to modify the data.

To allow multiple readers to access a resource at the same time we can use pthread_rwlock_t in pthreads. The pthread_rwlock_t which is a read,write lock allows multiple readers to access the resource, but allows only one reader at any given time.

The initialization function for this s

int pthread_rwlock_init(pthread_rwlock_t *restrict rwlock,const pthread_rwlockattr_t *restrict attr); Where rwlock is the locking variable of the type pthread_rwlock_t attr is the attributes of the lock, which can be set to NULL for default attributes.

Thus we can use the initialization function as

pthread_rwloc_t rwlock; pthread_rwlock_init(rwlock,NULL);

Once the lock is initialized we can lock a resource for writing using the function

int pthread_rwlock_wrlock(pthread_rwlock_t *rwlock);

Once the write lock is held no other process can access the resource until it is unlocked using

int pthread_rwlock_unlock(pthread_rwlock_t *rwlock);

To lock the resource only for reading and not writing we can use the function

int pthread_rwlock_rdlock(pthread_rwlock_t *rwlock);

Once the lock is held for reading, any number of other processes can access the resource of reading by locking the resource simultaneously. But the lock can not be held for writing, if it is already being held for reading. The lock can be unlocked using

int pthread_rwlock_rdlock(pthread_rwlock_t *rwlock);

To depict the working of rwlock let us look at the following example in which we create 4 threads, two for writing write_1,write_2, and two for reading,read_1,read_2.

We try to lock the rwlock in the following order

write_1->write_2->read_1->read_2

According to the above order we should not be able to get lock in write_1 and write_2 simultaneously but we should be able to get the lock simultaneously for read_1 and read_2.

#include <stdio.h> #include <pthread.h> #include <stdlib.h> pthread_rwlock_t rwlock; void * write(void *temp) { char *ret; FILE *file1; char *str; ret=pthread_rwlock_wrlock(&rwlock); printf("\nFile locked, please enter the message \n"); str=(char *)malloc(10*sizeof(char)); file1=fopen("temp","w"); scanf("%s",str); fprintf(file1,"%s",str); fclose(file1); pthread_rwlock_unlock(&rwlock); printf("\nUnlocked the file you can read it now \n"); return ret; } void * write_2(void *temp) { char *ret; FILE *file1; char *str; sleep(3); ret=pthread_rwlock_wrlock(&rwlock); printf("\nFile locked, please enter the message \n"); str=(char *)malloc(10*sizeof(char)); file1=fopen("temp","a"); scanf("%s",str); fprintf(file1,"%s",str); fclose(file1); pthread_rwlock_unlock(&rwlock); printf("\nUnlocked the file you can read it now \n"); return ret; } void * read_1(void *temp) { char *ret; FILE *file1; char *str; sleep(5); pthread_rwlock_rdlock(&rwlock); printf("\n1 Opening file for reading\n"); file1=fopen("temp","r"); str=(char *)malloc(10*sizeof(char)); fscanf(file1,"%s",str); printf("\nMessage from file is %s \n",str); sleep(3); fclose(file1); printf("\nUnlocking rwlock\n"); pthread_rwlock_unlock(&rwlock); return ret; } void * read_2(void *temp) { char *ret; FILE *file1; char *str; sleep(6); pthread_rwlock_rdlock(&rwlock); printf("\n2 Opening file for reading\n"); file1=fopen("temp","r"); str=(char *)malloc(10*sizeof(char)); fscanf(file1,"%s",str); printf("\nMessage from file is %s \n",str); fclose(file1); pthread_rwlock_rdlock(&rwlock); return ret; } main() { pthread_t thread_id,thread_id1,thread_id3,thread_id4; pthread_attr_t attr; int ret; void *res; pthread_rwlock_init(&rwlock,NULL); ret=pthread_create(&thread_id,NULL,&write,NULL); ret=pthread_create(&thread_id1,NULL,&read_1,NULL); ret=pthread_create(&thread_id3,NULL,&read_2,NULL); ret=pthread_create(&thread_id4,NULL,&write_2,NULL); printf("\n Created thread"); pthread_join(thread_id,&res); pthread_join(thread_id1,&res); pthread_join(thread_id3,&res); pthread_join(thread_id4,&res); pthread_rwlock_destroy(&rwlock); }

Save the above code as rw_lock.c

Compile it using the -lpthread flag

$ cc -lpthread rw_lock.c -o rw_lock $ ./rw_lock Created thread File locked, please enter the message Hello Unlocked the file you can read it now File locked, please enter the message World Unlocked the file you can read it now 1 Opening file for reading Message from file is HelloWorld 2 Opening file for reading Message from file is HelloWorld Unlocking rwlock

From the output we can see that the two writes were executed one after the other. But in case of reads, even though read_1 had not unlocked the rwlock, read_2 was allowed into the critical section and read the file. Thus indicating that multiple readers are allowed but only one writer is allowed into the critical section.

kbleds.c for linux kernel version 3.7.5

The example of blinking led given at "http://www.tldp.org/LDP/lkmpg/2.6/html/lkmpg.html#AEN1201 " works fine for kernel versions before 2.6.36, but for version above that it fails to compile due the changes in the structure vc_data and ioctl call of tty_driver.

Here is the modified code tested and working on 3.7.5.

The changes are

1. change the the vc_tty pointer to port.tty

vc_cons[fg_console].d->vc_tty to vc_cons[fg_console].d->port.tty

2. Remove the argument "NULL" being passed to the ioctl call of tty driver.

(my_driver->ops->ioctl) (vc_cons[fg_console].d->port.tty, NULL, KDSETLED,*pstatus); to (my_driver->ops->ioctl) (vc_cons[fg_console].d->port.tty, KDSETLED, *pstatus);

Full code:

/* * kbleds.c − Blink keyboard leds until the module is unloaded.(modified for 3.7.5) */ #include <linux/module.h> #include <linux/configfs.h> #include <linux/init.h> #include <linux/tty.h> /* For fg_console, MAX_NR_CONSOLES */ #include <linux/kd.h> /* For KDSETLED */ #include <linux/vt.h> #include <linux/console_struct.h> /* For vc_cons */ #include <linux/vt_kern.h> MODULE_DESCRIPTION("Example module illustrating the use of Keyboard LEDs."); MODULE_LICENSE("GPL"); struct timer_list my_timer; struct tty_driver *my_driver; char kbledstatus = 0; #define BLINK_DELAY HZ/5 #define ALL_LEDS_ON 0x07 #define RESTORE_LEDS 0xFF /* * Function my_timer_func blinks the keyboard LEDs periodically by invoking * command KDSETLED of ioctl() on the keyboard driver. To learn more on virtual * terminal ioctl operations, please see file: * /usr/src/linux/drivers/char/vt_ioctl.c, function vt_ioctl(). * * The argument to KDSETLED is alternatively set to 7 (thus causing the led * mode to be set to LED_SHOW_IOCTL, and all the leds are lit) and to 0xFF * (any value above 7 switches back the led mode to LED_SHOW_FLAGS, thus * the LEDs reflect the actual keyboard status). To learn more on this, * please see file: * /usr/src/linux/drivers/char/keyboard.c, function setledstate(). * */ static void my_timer_func(unsigned long ptr) { int *pstatus = (int *)ptr; if (*pstatus == ALL_LEDS_ON) *pstatus = RESTORE_LEDS; else *pstatus = ALL_LEDS_ON; (my_driver->ops->ioctl) (vc_cons[fg_console].d->port.tty, KDSETLED, *pstatus); my_timer.expires = jiffies + BLINK_DELAY; add_timer(&my_timer); } static int __init kbleds_init(void) { int i; printk(KERN_INFO "kbleds: loading\n"); printk(KERN_INFO "kbleds: fgconsole is %x\n", fg_console); for (i = 0; i < MAX_NR_CONSOLES; i++) { if (!vc_cons[i].d) break; printk(KERN_INFO "poet_atkm: console[%i/%i] #%i, tty %lx\n", i, MAX_NR_CONSOLES, vc_cons[i].d->vc_num, (unsigned long)vc_cons[i].d->port.tty); } printk(KERN_INFO "kbleds: finished scanning consoles\n"); my_driver = vc_cons[fg_console].d->port.tty->driver; printk(KERN_INFO "kbleds: tty driver magic %x\n", my_driver->magic); /* * Set up the LED blink timer the first time */ init_timer(&my_timer); my_timer.function = my_timer_func; my_timer.data = (unsigned long)&kbledstatus; my_timer.expires = jiffies + BLINK_DELAY; add_timer(&my_timer); return 0; } static void __exit kbleds_cleanup(void) { printk(KERN_INFO "kbleds: unloading...\n"); del_timer(&my_timer); (my_driver->ops->ioctl) (vc_cons[fg_console].d->port.tty, KDSETLED, RESTORE_LEDS); } module_init(kbleds_init); module_exit(kbleds_cleanup);

Now save the file as kbleds.c

Compile it using the makefile

obj-m += kbleds.o all: make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules clean: make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

Insert it into the kernel using insmod

$ insmod kbleds.ko

The key board leds should start to blink as soon as the module is inserted and will continue to blink as long as we do not remove the module using rmmmod

$ rmmmod kbleds

or reboot the system.

Creating letter drop effect using gimp in linux

Here is how we can create the animated effect of letters dropping on to a page, as shown below, using gimp.

Note:This was done using gimp2.6

First to be able to create the effect we need to install the additional gimp package called gimp-gap i.e. in ubuntu based systems run the command

sudo apt-get install gimp-gap

After the installation is done launch gimp and go to

file->create->Fx-Foundry->animation->letter Drop

We will see a prompt as shown below.

In the text field enter the text for which the animation has to be created.
The foreground color is the color of the text and the background color is the of the background of the text, we can choose the color we want by clicking on each of them and selecting from the range of colors .

Letter delay field is to specify the delay between the letters appearing in the animation
Word delay is the delay between words in case there are multiple words in the text
Starting size is the size of the font with which the animation will start, the size will slowly decrease with each fram giving the dropping effect
The ending size is the final size of the text.
Frames per letter is the number of frames that you want to use for every letter in the animation. The more the number of frames the more detailed the animation will look.
Click on Ok and wait for gimp to do the magic. Once it is done we should see the following screen.

To check if the animation suits your requirements you can see the preview by going to

filters->animation->playback

The following window will pop up, click the play button on the top left to see the animation.

If satisfied with the result, close the preview window and Click on

file->saves as

Enter the name for the file and add the extension .gif at the end.
In the file types option at the bottom right chose gif.

The prompt will be shown asking for confirmation whether the image should be stored as animation or as a flat image, choose save as animation

If the image size is big,a prompt for cropping the image might appear, choose crop and see if it affects your image or not.

The final prompt will allow to choose whether the animation should loop for ever or not.

The delay between frames can be specified in this has been specified next to layers itself, thus you can leave the default value of delay between frames as it does not affect the animation.

Click on save and the letter drop animation should be ready for use.