On 2020/1/17 下午3:57, Takashi Iwai wrote:
On Fri, 17 Jan 2020 06:30:18 +0100,
Keyon Jie wrote:
On 2020/1/17 上午4:37, Takashi Iwai wrote:
Hi Takashi, I get your concern here, but if we switch to use dma_max
limit, we won't change the preallocated buffer, it will be still 64KB
for each stream, user space can ask for re-allocate buffer for each
stream up to 32MB, but those pinned and can't be swapped out ones are
the 64KB preallocated ones only, am I wrong?
No, in general, all sound hardware buffers are pinned.
Sorry, I must have been wrong here, what I was focusing on is those
allocated SG DMA buffers, I am not sure if they are those you called
"hardware buffers" here.
My understanding was like this:
1. in pcm_new() stage, the device PCM driver should call
snd_pcm_lib_preallocate_pages()->
snd_pcm_lib_preallocate_pages()->
preallocate_pcm_pages()
and then the substream->dma_buffer is initialized with the preallocated
buffer.
2. in pcm_open() stage, the device PCM driver should call
snd_pcm_lib_malloc_pages()->
snd_dma_alloc_pages() //if we need to reallocate bigger buffer. *The
substream->dma_buffer won't be freed, Takashi, this is what I thought
you named "pinned" buffer.* And those reallocated bigger buffer via
snd_dma_alloc_pages() will be freed at pcm_close() per my understanding?
Thanks,
~Keyon
Takashi
_______________________________________________
Alsa-devel mailing list
Alsa-devel@xxxxxxxxxxxxxxxx
https://mailman.alsa-project.org/mailman/listinfo/alsa-devel
_______________________________________________
Alsa-devel mailing list
Alsa-devel@xxxxxxxxxxxxxxxx
https://mailman.alsa-project.org/mailman/listinfo/alsa-devel
