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linux-next/sound/last.c
Takashi Iwai f4fa968950 ALSA: core: Don't refer to snd_cards array directly
The snd_cards[] array holds the card pointers that have been currently
registered, and it's exported for the external modules that may need
to refer a card object.  But accessing to this array can be racy
against the driver probe or removal, as the card registration or free
may happen concurrently.

This patch gets rid of the direct access to snd_cards[] array and
provides a helper function to give the card object from the index
number with a refcount management.  Then the caller can access to the
given card object safely, and releases it via snd_card_unref().

While we're at it, add a proper comment to snd_card_unref() and make
it an inlined function for type-safety, too.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
2019-04-17 07:16:15 +02:00

45 lines
1.3 KiB
C

/*
* Advanced Linux Sound Architecture
* Copyright (c) by Jaroslav Kysela <perex@perex.cz>
*
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
#include <linux/init.h>
#include <sound/core.h>
static int __init alsa_sound_last_init(void)
{
struct snd_card *card;
int idx, ok = 0;
printk(KERN_INFO "ALSA device list:\n");
for (idx = 0; idx < SNDRV_CARDS; idx++) {
card = snd_card_ref(idx);
if (card) {
printk(KERN_INFO " #%i: %s\n", idx, card->longname);
snd_card_unref(card);
ok++;
}
}
if (ok == 0)
printk(KERN_INFO " No soundcards found.\n");
return 0;
}
late_initcall_sync(alsa_sound_last_init);