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Commit 53e7bf45 authored by Takashi Iwai's avatar Takashi Iwai
Browse files

ALSA: control: Simplify snd_ctl_elem_list() implementation 



This patch simplifies the code of snd_ctl_elem_list() in the following
ways:

- Avoid a vmalloc() temporary buffer but do copy in each iteration;
  the vmalloc buffer was introduced at the time we took the spinlock
  for the ctl element management.

- Use the standard list_for_each_entry() macro

- Merge two loops into one;
  it used to be a loop for skipping until offset becomes zero and
  another loop to copy the data.  They can be folded into a single
  loop easily.

Reviewed-by: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
Tested-by: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent a02cb8f8

sound/core/control.c

+24 −42
Original line number Diff line number Diff line
@@ -747,11 +747,11 @@ static int snd_ctl_card_info(struct snd_card *card, struct snd_ctl_file * ctl, 
static int snd_ctl_elem_list(struct snd_card *card,

			     struct snd_ctl_elem_list __user *_list)

{

	struct list_head *plist;

	struct snd_ctl_elem_list list;

	struct snd_kcontrol *kctl;

	struct snd_ctl_elem_id *dst, *id;

	struct snd_ctl_elem_id id;

	unsigned int offset, space, jidx;

	int err = 0;

	

	if (copy_from_user(&list, _list, sizeof(list)))

		return -EFAULT;
@@ -760,52 +760,34 @@ static int snd_ctl_elem_list(struct snd_card *card, 
	/* try limit maximum space */

	if (space > 16384)

		return -ENOMEM;

	if (space > 0) {

		/* allocate temporary buffer for atomic operation */

		dst = vmalloc(space * sizeof(struct snd_ctl_elem_id));

		if (dst == NULL)

			return -ENOMEM;

	down_read(&card->controls_rwsem);

	list.count = card->controls_count;

		plist = card->controls.next;

		while (plist != &card->controls) {

			if (offset == 0)

				break;

			kctl = snd_kcontrol(plist);

			if (offset < kctl->count)

				break;

	list.used = 0;

	if (space > 0) {

		list_for_each_entry(kctl, &card->controls, list) {

			if (offset >= kctl->count) {

				offset -= kctl->count;

			plist = plist->next;

				continue;

			}

			for (jidx = offset; jidx < kctl->count; jidx++) {

				snd_ctl_build_ioff(&id, kctl, jidx);

				if (copy_to_user(list.pids + list.used, &id,

						 sizeof(id))) {

					err = -EFAULT;

					goto out;

				}

		list.used = 0;

		id = dst;

		while (space > 0 && plist != &card->controls) {

			kctl = snd_kcontrol(plist);

			for (jidx = offset; space > 0 && jidx < kctl->count; jidx++) {

				snd_ctl_build_ioff(id, kctl, jidx);

				id++;

				space--;

				list.used++;

				if (!--space)

					goto out;

			}

			plist = plist->next;

			offset = 0;

		}

		up_read(&card->controls_rwsem);

		if (list.used > 0 &&

		    copy_to_user(list.pids, dst,

				 list.used * sizeof(struct snd_ctl_elem_id))) {

			vfree(dst);

			return -EFAULT;

	}

		vfree(dst);

	} else {

		down_read(&card->controls_rwsem);

		list.count = card->controls_count;

 out:

	up_read(&card->controls_rwsem);

	}

	if (copy_to_user(_list, &list, sizeof(list)))

		return -EFAULT;

	return 0;

	if (!err && copy_to_user(_list, &list, sizeof(list)))

		err = -EFAULT;

	return err;

}



static bool validate_element_member_dimension(struct snd_ctl_elem_info *info)