Messages in this thread |  | | From | Denys Vlasenko <> | Subject | sound: -EPERM on first mplayer invocation | Date | Sun, 2 Aug 2009 23:36:48 +0200 |
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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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