On 25.02.2021 11:55, Takashi Iwai wrote:
On Mon, 22 Feb 2021 16:34:41 +0100, Anton Yakovlev wrote:
+static int virtsnd_pcm_open(struct snd_pcm_substream *substream) +{
struct virtio_pcm *vpcm = snd_pcm_substream_chip(substream);struct virtio_pcm_substream *vss = NULL;if (vpcm) {switch (substream->stream) {case SNDRV_PCM_STREAM_PLAYBACK:case SNDRV_PCM_STREAM_CAPTURE: {The switch() here looks superfluous. The substream->stream must be a good value in the callback. If any, you can put WARN_ON() there, but I don't think it worth.
At least it doesn't do any harm. If something really went wrong, we can check it right in the open callback, which is called the very first.
+static int virtsnd_pcm_hw_params(struct snd_pcm_substream *substream,
struct snd_pcm_hw_params *hw_params)+{
....
return virtsnd_pcm_msg_alloc(vss, periods, period_bytes);We have the allocation, but...
+static int virtsnd_pcm_hw_free(struct snd_pcm_substream *substream) +{
return 0;... no release at hw_free()? I know that the free is present in the allocator, but it's only for re-allocation case, I suppose.
When the substream stops, sync_ptr waits until the device has completed all pending messages. This wait can be interrupted either by a signal or due to a timeout. In this case, the device can still access messages even after calling hw_free(). It can also issue an interrupt, and the interrupt handler will also try to access message structures. Therefore, freeing of already allocated messages occurs either in hw_params() or in dev->release(), since there it is 100% safe.
thanks,
Takashi