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![Joe Korty](/assets/img/avatar_default.png)
Make baby-simple the code for /proc/devices. Based on the proven design for /proc/interrupts. This also fixes the early-termination regression 2.6.16 introduced, as demonstrated by: # dd if=/proc/devices bs=1 Character devices: 1 mem 27+0 records in 27+0 records out This should also work (but is untested) when /proc/devices >4096 bytes, which I believe is what the original 2.6.16 rewrite fixed. [akpm@osdl.org: cleanups, simplifications] Signed-off-by: Joe Korty <joe.korty@ccur.com> Cc: Neil Horman <nhorman@tuxdriver.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
443 lines
9.2 KiB
C
443 lines
9.2 KiB
C
/*
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* linux/fs/char_dev.c
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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*/
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#include <linux/config.h>
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#include <linux/init.h>
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#include <linux/fs.h>
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#include <linux/slab.h>
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#include <linux/string.h>
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#include <linux/major.h>
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#include <linux/errno.h>
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#include <linux/module.h>
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#include <linux/smp_lock.h>
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#include <linux/devfs_fs_kernel.h>
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#include <linux/seq_file.h>
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#include <linux/kobject.h>
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#include <linux/kobj_map.h>
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#include <linux/cdev.h>
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#include <linux/mutex.h>
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#ifdef CONFIG_KMOD
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#include <linux/kmod.h>
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#endif
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static struct kobj_map *cdev_map;
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static DEFINE_MUTEX(chrdevs_lock);
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static struct char_device_struct {
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struct char_device_struct *next;
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unsigned int major;
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unsigned int baseminor;
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int minorct;
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char name[64];
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struct file_operations *fops;
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struct cdev *cdev; /* will die */
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} *chrdevs[CHRDEV_MAJOR_HASH_SIZE];
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/* index in the above */
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static inline int major_to_index(int major)
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{
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return major % CHRDEV_MAJOR_HASH_SIZE;
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}
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#ifdef CONFIG_PROC_FS
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void chrdev_show(struct seq_file *f, off_t offset)
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{
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struct char_device_struct *cd;
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if (offset < CHRDEV_MAJOR_HASH_SIZE) {
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mutex_lock(&chrdevs_lock);
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for (cd = chrdevs[offset]; cd; cd = cd->next)
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seq_printf(f, "%3d %s\n", cd->major, cd->name);
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mutex_unlock(&chrdevs_lock);
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}
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}
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#endif /* CONFIG_PROC_FS */
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/*
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* Register a single major with a specified minor range.
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*
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* If major == 0 this functions will dynamically allocate a major and return
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* its number.
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*
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* If major > 0 this function will attempt to reserve the passed range of
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* minors and will return zero on success.
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*
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* Returns a -ve errno on failure.
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*/
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static struct char_device_struct *
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__register_chrdev_region(unsigned int major, unsigned int baseminor,
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int minorct, const char *name)
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{
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struct char_device_struct *cd, **cp;
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int ret = 0;
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int i;
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cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
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if (cd == NULL)
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return ERR_PTR(-ENOMEM);
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mutex_lock(&chrdevs_lock);
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/* temporary */
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if (major == 0) {
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for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
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if (chrdevs[i] == NULL)
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break;
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}
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if (i == 0) {
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ret = -EBUSY;
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goto out;
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}
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major = i;
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ret = major;
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}
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cd->major = major;
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cd->baseminor = baseminor;
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cd->minorct = minorct;
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strncpy(cd->name,name, 64);
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i = major_to_index(major);
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for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
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if ((*cp)->major > major ||
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((*cp)->major == major && (*cp)->baseminor >= baseminor))
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break;
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if (*cp && (*cp)->major == major &&
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(*cp)->baseminor < baseminor + minorct) {
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ret = -EBUSY;
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goto out;
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}
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cd->next = *cp;
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*cp = cd;
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mutex_unlock(&chrdevs_lock);
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return cd;
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out:
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mutex_unlock(&chrdevs_lock);
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kfree(cd);
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return ERR_PTR(ret);
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}
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static struct char_device_struct *
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__unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
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{
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struct char_device_struct *cd = NULL, **cp;
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int i = major_to_index(major);
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mutex_lock(&chrdevs_lock);
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for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
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if ((*cp)->major == major &&
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(*cp)->baseminor == baseminor &&
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(*cp)->minorct == minorct)
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break;
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if (*cp) {
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cd = *cp;
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*cp = cd->next;
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}
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mutex_unlock(&chrdevs_lock);
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return cd;
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}
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int register_chrdev_region(dev_t from, unsigned count, const char *name)
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{
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struct char_device_struct *cd;
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dev_t to = from + count;
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dev_t n, next;
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for (n = from; n < to; n = next) {
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next = MKDEV(MAJOR(n)+1, 0);
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if (next > to)
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next = to;
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cd = __register_chrdev_region(MAJOR(n), MINOR(n),
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next - n, name);
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if (IS_ERR(cd))
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goto fail;
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}
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return 0;
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fail:
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to = n;
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for (n = from; n < to; n = next) {
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next = MKDEV(MAJOR(n)+1, 0);
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kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
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}
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return PTR_ERR(cd);
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}
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int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
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const char *name)
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{
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struct char_device_struct *cd;
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cd = __register_chrdev_region(0, baseminor, count, name);
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if (IS_ERR(cd))
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return PTR_ERR(cd);
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*dev = MKDEV(cd->major, cd->baseminor);
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return 0;
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}
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int register_chrdev(unsigned int major, const char *name,
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const struct file_operations *fops)
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{
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struct char_device_struct *cd;
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struct cdev *cdev;
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char *s;
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int err = -ENOMEM;
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cd = __register_chrdev_region(major, 0, 256, name);
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if (IS_ERR(cd))
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return PTR_ERR(cd);
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cdev = cdev_alloc();
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if (!cdev)
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goto out2;
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cdev->owner = fops->owner;
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cdev->ops = fops;
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kobject_set_name(&cdev->kobj, "%s", name);
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for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/'))
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*s = '!';
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err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
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if (err)
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goto out;
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cd->cdev = cdev;
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return major ? 0 : cd->major;
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out:
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kobject_put(&cdev->kobj);
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out2:
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kfree(__unregister_chrdev_region(cd->major, 0, 256));
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return err;
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}
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void unregister_chrdev_region(dev_t from, unsigned count)
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{
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dev_t to = from + count;
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dev_t n, next;
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for (n = from; n < to; n = next) {
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next = MKDEV(MAJOR(n)+1, 0);
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if (next > to)
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next = to;
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kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
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}
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}
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int unregister_chrdev(unsigned int major, const char *name)
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{
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struct char_device_struct *cd;
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cd = __unregister_chrdev_region(major, 0, 256);
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if (cd && cd->cdev)
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cdev_del(cd->cdev);
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kfree(cd);
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return 0;
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}
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static DEFINE_SPINLOCK(cdev_lock);
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static struct kobject *cdev_get(struct cdev *p)
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{
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struct module *owner = p->owner;
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struct kobject *kobj;
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if (owner && !try_module_get(owner))
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return NULL;
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kobj = kobject_get(&p->kobj);
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if (!kobj)
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module_put(owner);
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return kobj;
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}
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void cdev_put(struct cdev *p)
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{
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if (p) {
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struct module *owner = p->owner;
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kobject_put(&p->kobj);
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module_put(owner);
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}
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}
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/*
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* Called every time a character special file is opened
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*/
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int chrdev_open(struct inode * inode, struct file * filp)
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{
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struct cdev *p;
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struct cdev *new = NULL;
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int ret = 0;
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spin_lock(&cdev_lock);
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p = inode->i_cdev;
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if (!p) {
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struct kobject *kobj;
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int idx;
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spin_unlock(&cdev_lock);
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kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
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if (!kobj)
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return -ENXIO;
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new = container_of(kobj, struct cdev, kobj);
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spin_lock(&cdev_lock);
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p = inode->i_cdev;
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if (!p) {
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inode->i_cdev = p = new;
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inode->i_cindex = idx;
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list_add(&inode->i_devices, &p->list);
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new = NULL;
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} else if (!cdev_get(p))
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ret = -ENXIO;
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} else if (!cdev_get(p))
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ret = -ENXIO;
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spin_unlock(&cdev_lock);
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cdev_put(new);
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if (ret)
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return ret;
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filp->f_op = fops_get(p->ops);
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if (!filp->f_op) {
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cdev_put(p);
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return -ENXIO;
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}
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if (filp->f_op->open) {
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lock_kernel();
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ret = filp->f_op->open(inode,filp);
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unlock_kernel();
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}
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if (ret)
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cdev_put(p);
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return ret;
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}
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void cd_forget(struct inode *inode)
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{
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spin_lock(&cdev_lock);
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list_del_init(&inode->i_devices);
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inode->i_cdev = NULL;
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spin_unlock(&cdev_lock);
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}
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static void cdev_purge(struct cdev *cdev)
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{
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spin_lock(&cdev_lock);
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while (!list_empty(&cdev->list)) {
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struct inode *inode;
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inode = container_of(cdev->list.next, struct inode, i_devices);
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list_del_init(&inode->i_devices);
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inode->i_cdev = NULL;
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}
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spin_unlock(&cdev_lock);
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}
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/*
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* Dummy default file-operations: the only thing this does
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* is contain the open that then fills in the correct operations
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* depending on the special file...
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*/
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const struct file_operations def_chr_fops = {
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.open = chrdev_open,
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};
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static struct kobject *exact_match(dev_t dev, int *part, void *data)
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{
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struct cdev *p = data;
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return &p->kobj;
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}
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static int exact_lock(dev_t dev, void *data)
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{
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struct cdev *p = data;
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return cdev_get(p) ? 0 : -1;
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}
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int cdev_add(struct cdev *p, dev_t dev, unsigned count)
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{
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p->dev = dev;
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p->count = count;
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return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
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}
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static void cdev_unmap(dev_t dev, unsigned count)
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{
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kobj_unmap(cdev_map, dev, count);
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}
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void cdev_del(struct cdev *p)
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{
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cdev_unmap(p->dev, p->count);
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kobject_put(&p->kobj);
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}
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static void cdev_default_release(struct kobject *kobj)
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{
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struct cdev *p = container_of(kobj, struct cdev, kobj);
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cdev_purge(p);
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}
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static void cdev_dynamic_release(struct kobject *kobj)
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{
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struct cdev *p = container_of(kobj, struct cdev, kobj);
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cdev_purge(p);
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kfree(p);
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}
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static struct kobj_type ktype_cdev_default = {
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.release = cdev_default_release,
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};
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static struct kobj_type ktype_cdev_dynamic = {
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.release = cdev_dynamic_release,
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};
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struct cdev *cdev_alloc(void)
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{
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struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
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if (p) {
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p->kobj.ktype = &ktype_cdev_dynamic;
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INIT_LIST_HEAD(&p->list);
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kobject_init(&p->kobj);
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}
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return p;
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}
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void cdev_init(struct cdev *cdev, const struct file_operations *fops)
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{
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memset(cdev, 0, sizeof *cdev);
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INIT_LIST_HEAD(&cdev->list);
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cdev->kobj.ktype = &ktype_cdev_default;
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kobject_init(&cdev->kobj);
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cdev->ops = fops;
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}
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static struct kobject *base_probe(dev_t dev, int *part, void *data)
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{
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if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
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/* Make old-style 2.4 aliases work */
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request_module("char-major-%d", MAJOR(dev));
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return NULL;
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}
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void __init chrdev_init(void)
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{
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cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
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}
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/* Let modules do char dev stuff */
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EXPORT_SYMBOL(register_chrdev_region);
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EXPORT_SYMBOL(unregister_chrdev_region);
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EXPORT_SYMBOL(alloc_chrdev_region);
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EXPORT_SYMBOL(cdev_init);
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EXPORT_SYMBOL(cdev_alloc);
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EXPORT_SYMBOL(cdev_del);
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EXPORT_SYMBOL(cdev_add);
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EXPORT_SYMBOL(register_chrdev);
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EXPORT_SYMBOL(unregister_chrdev);
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