V4L/DVB (10641): v4l2-dev: remove limit of 32 devices per driver in get_index()

get_index() had a limitation of 32 devices per driver. This was
unnecessarily strict and has been replaced with the maximum number
of devices. That should really satisfy anyone!

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 13 insertions, 12 deletions

diff --git a/drivers/media/video/v4l2-dev.c b/drivers/media/video/v4l2-dev.c
index 13f87c22e78d..922b39e79b8e 100644
--- a/drivers/media/video/v4l2-dev.c
+++ b/drivers/media/video/v4l2-dev.c
@@ -288,37 +288,38 @@ static const struct file_operations v4l2_fops = {
  */
 static int get_index(struct video_device *vdev, int num)
 {
-        u32 used = 0;
-        const int max_index = sizeof(used) * 8 - 1;
+        /* This can be static since this function is called with the global
+           videodev_lock held. */
+        static DECLARE_BITMAP(used, VIDEO_NUM_DEVICES);
         int i;
 
-        /* Currently a single v4l driver instance cannot create more than
-           32 devices.
-           Increase to u64 or an array of u32 if more are needed. */
-        if (num > max_index) {
+        if (num >= VIDEO_NUM_DEVICES) {
                 printk(KERN_ERR "videodev: %s num is too large\n", __func__);
                 return -EINVAL;
         }
 
-        /* Some drivers do not set the parent. In that case always return 0. */
+        /* Some drivers do not set the parent. In that case always return
+           num or 0. */
         if (vdev->parent == NULL)
-                return 0;
+                return num >= 0 ? num : 0;
+
+        bitmap_zero(used, VIDEO_NUM_DEVICES);
 
         for (i = 0; i < VIDEO_NUM_DEVICES; i++) {
                 if (video_device[i] != NULL &&
                     video_device[i]->parent == vdev->parent) {
-                        used |= 1 << video_device[i]->index;
+                        set_bit(video_device[i]->index, used);
                 }
         }
 
         if (num >= 0) {
-                if (used & (1 << num))
+                if (test_bit(num, used))
                         return -ENFILE;
                 return num;
         }
 
-        i = ffz(used);
-        return i > max_index ? -ENFILE : i;
+        i = find_first_zero_bit(used, VIDEO_NUM_DEVICES);
+        return i == VIDEO_NUM_DEVICES ? -ENFILE : i;
 }
 
 int video_register_device(struct video_device *vdev, int type, int nr)