@@ -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)
@@ -492,7 +501,7 @@ 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)) {
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 sub-effect to issue appl_ptr unexpectedly. This commit adds a helper function to issue avail_min without the sub-effect. Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp> --- src/pcm/pcm_hw.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)