[alsa-devel] [PATCH] ALSA: control: confirm to return all identical information in 'activate' event data
Takashi Iwai
tiwai at suse.de
Mon Feb 9 16:28:33 CET 2015
At Tue, 10 Feb 2015 00:02:06 +0900,
Takashi Sakamoto wrote:
>
> When event originator doesn't set numerical ID in identical information,
> the event data includes no numerical ID, thus userspace applications
> cannot identify the control just by unique ID in event data.
>
> This commit fix this bug so as the event data includes all of identical
> information.
>
> Signed-off-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>
You can't overwrite id pointer in this case. It's a caller's object.
One way to fix would be to copy the id instance. Another way would be
to change up/down_write() with _read(), and include snd_ctl_notify()
call with kctl->id inside the semaphore lock.
The former would be less changes but consume the stack significantly.
thanks,
Takashi
> ---
> sound/core/control.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/sound/core/control.c b/sound/core/control.c
> index 6a72b3e..884fddd 100644
> --- a/sound/core/control.c
> +++ b/sound/core/control.c
> @@ -587,6 +587,7 @@ int snd_ctl_activate_id(struct snd_card *card, struct snd_ctl_elem_id *id,
> }
> ret = 1;
> unlock:
> + *id = kctl->id;
> up_write(&card->controls_rwsem);
> if (ret > 0)
> snd_ctl_notify(card, SNDRV_CTL_EVENT_MASK_INFO, id);
> --
> 2.1.0
>
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