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pcm: hw: add a helper function to issue avail_min without side-effects

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At present, applications can change avail_min parameter of PCM substream
by two ways; via mapped control data, and by executing ioctl(2) with
SNDRV_PCM_IOCTL_SYNC_PTR. The former is available in a case that the
applications map the data successfully.

When utilizing alsa-lib API, the above is done by a call of
'snd_pcm_sw_params()' to hw PCM plugin. In current implementation, this
call has an side-effect to issue appl_ptr unexpectedly.

This commit adds a helper function to issue avail_min without the
side-effect.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Sakamoto 2017-06-30 20:37:28 +09:00 • committed by Takashi Iwai
parent de9fe69e40
commit cea81cbdc2
1 changed files with 10 additions and 1 deletions
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11
src/pcm/pcm_hw.c
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@ -151,6 +151,15 @@ static int sync_ptr(snd_pcm_hw_t *hw, unsigned int flags)
return 0;
}
static int issue_avail_min(snd_pcm_hw_t *hw)
{
if (!hw->mmap_control_fallbacked)
return 0;
/* Avoid unexpected change of applptr in kernel space. */
return sync_ptr1(hw, SNDRV_PCM_SYNC_PTR_APPL);
}
static int issue_applptr(snd_pcm_hw_t *hw)
{
if (!hw->mmap_control_fallbacked)
@ -506,7 +515,7 @@ static int snd_pcm_hw_sw_params(snd_pcm_t *pcm, snd_pcm_sw_params_t * params)
params->silence_size == pcm->silence_size &&
old_period_event == hw->period_event) {
hw->mmap_control->avail_min = params->avail_min;
return sync_ptr(hw, 0);
return issue_avail_min(hw);
}
if (params->tstamp_type == SND_PCM_TSTAMP_TYPE_MONOTONIC_RAW &&
hw->version < SNDRV_PROTOCOL_VERSION(2, 0, 12)) {