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Message-Id: <200908022336.48898.vda.linux@googlemail.com>
Date: Sun, 2 Aug 2009 23:36:48 +0200
From: Denys Vlasenko <vda.linux@...glemail.com>
To: Takashi Iwai <tiwai@...e.de>
Cc: linux-kernel@...r.kernel.org
Subject: sound: -EPERM on first mplayer invocation
Hi,
For a long time I observe the following nuisance:
when I run mplayer for the very first time after boot,
I can't adjust the volume. mplayer spews this to stderr:
alsa-control: error setting left channel, Operation not permitted
This happens even if I login as root and run mplayer as root.
I tracked it down to snd_ctl_elem_write in sound/core/control.c
static int snd_ctl_elem_write(struct snd_card *card, struct snd_ctl_file *file,
struct snd_ctl_elem_value *control)
{
struct snd_kcontrol *kctl;
struct snd_kcontrol_volatile *vd;
unsigned int index_offset;
int result;
down_read(&card->controls_rwsem);
kctl = snd_ctl_find_id(card, &control->id);
if (kctl == NULL) {
result = -ENOENT;
} else {
index_offset = snd_ctl_get_ioff(kctl, &control->id);
vd = &kctl->vd[index_offset];
if (!(vd->access & SNDRV_CTL_ELEM_ACCESS_WRITE) ||
kctl->put == NULL ||
(file && vd->owner && vd->owner != file)) {
printk("EPERM:\n");
printk("vd->access & SNDRV_CTL_ELEM_ACCESS_WRITE:%x\n", vd->access & SNDRV_CTL_ELEM_ACCESS_WRITE);
printk("kctl->put:%p\n", kctl->put);
printk("file:%p vd->owner:%p\n", file, vd->owner);
result = -EPERM;
} else {
The above printk triggers and prints:
EPERM:
vd->access & SNDRV_CTL_ELEM_ACCESS_WRITE:2
kctl->put:ffffffffa009e8de
file:ffff88007c56a5c0 vd->owner:ffff88007bc34740
Thus, vd->owner != file.
As I said, it only happens on very first run of mplayer,
and it isn't a recent change, I think I saw it at least
for one year with different kernels.
Takashi, any idea what might be happening here?
How can I help you more with tracking it down?
--
vda
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