[PATCH] Simplify proc/devices and fix early termination regression

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>

1 files changed, 11 insertions, 76 deletions

diff --git a/fs/char_dev.c b/fs/char_dev.c
index 4e1b849f912f..f3418f7a6e9d 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -15,6 +15,7 @@
 #include <linux/module.h>
 #include <linux/smp_lock.h>
 #include <linux/devfs_fs_kernel.h>
+#include <linux/seq_file.h>
 
 #include <linux/kobject.h>
 #include <linux/kobj_map.h>
@@ -27,8 +28,6 @@
 
 static struct kobj_map *cdev_map;
 
-#define MAX_PROBE_HASH 255      /* random */
-
 static DEFINE_MUTEX(chrdevs_lock);
 
 static struct char_device_struct {
@@ -39,93 +38,29 @@ static struct char_device_struct {
         char name[64];
         struct file_operations *fops;
         struct cdev *cdev;              /* will die */
-} *chrdevs[MAX_PROBE_HASH];
+} *chrdevs[CHRDEV_MAJOR_HASH_SIZE];
 
 /* index in the above */
 static inline int major_to_index(int major)
 {
-        return major % MAX_PROBE_HASH;
-}
-
-struct chrdev_info {
-        int index;
-        struct char_device_struct *cd;
-};
-
-void *get_next_chrdev(void *dev)
-{
-        struct chrdev_info *info;
-
-        if (dev == NULL) {
-                info = kmalloc(sizeof(*info), GFP_KERNEL);
-                if (!info)
-                        goto out;
-                info->index=0;
-                info->cd = chrdevs[info->index];
-                if (info->cd)
-                        goto out;
-        } else {
-                info = dev;
-        }
-
-        while (info->index < ARRAY_SIZE(chrdevs)) {
-                if (info->cd)
-                        info->cd = info->cd->next;
-                if (info->cd)
-                        goto out;
-                /*
-                 * No devices on this chain, move to the next
-                 */
-                info->index++;
-                info->cd = (info->index < ARRAY_SIZE(chrdevs)) ?
-                        chrdevs[info->index] : NULL;
-                if (info->cd)
-                        goto out;
-        }
-
-out:
-        return info;
-}
-
-void *acquire_chrdev_list(void)
-{
-        mutex_lock(&chrdevs_lock);
-        return get_next_chrdev(NULL);
-}
-
-void release_chrdev_list(void *dev)
-{
-        mutex_unlock(&chrdevs_lock);
-        kfree(dev);
+        return major % CHRDEV_MAJOR_HASH_SIZE;
 }
 
+#ifdef CONFIG_PROC_FS
 
-int count_chrdev_list(void)
+void chrdev_show(struct seq_file *f, off_t offset)
 {
         struct char_device_struct *cd;
-        int i, count;
-
-        count = 0;
 
-        for (i = 0; i < ARRAY_SIZE(chrdevs) ; i++) {
-                for (cd = chrdevs[i]; cd; cd = cd->next)
-                        count++;
+        if (offset < CHRDEV_MAJOR_HASH_SIZE) {
+                mutex_lock(&chrdevs_lock);
+                for (cd = chrdevs[offset]; cd; cd = cd->next)
+                        seq_printf(f, "%3d %s\n", cd->major, cd->name);
+                mutex_unlock(&chrdevs_lock);
         }
-
-        return count;
 }
 
-int get_chrdev_info(void *dev, int *major, char **name)
-{
-        struct chrdev_info *info = dev;
-
-        if (info->cd == NULL)
-                return 1;
-
-        *major = info->cd->major;
-        *name = info->cd->name;
-        return 0;
-}
+#endif /* CONFIG_PROC_FS */
 
 /*
  * Register a single major with a specified minor range.