[alsa-devel] [PATCH] ALSA: snd-aloop: make preallocated buffer size configurable

[Takashi Iwai]

At Wed, 21 Sep 2011 10:02:27 -0500,
Pierre-Louis Bossart wrote:
> 
> > I meant to have a kconfig option to limit the upper-bound of pre-alloc
> > buffer sizes for all drivers.  That is, a patch like below (untested)
> 
> That's a good idea, but the two patches aren't necessarily exclusive. In an
> embedded solution you may want a 2s PCM buffer for low-power playback and a
> 64k buffer for snd-aloop as it is only used with small periods. Also one
> would need to check the buffer/period sizes in each driver, and make sure
> they are smaller than this global max.

Well, if it's only about snd-aloop, another option would be to use
vmalloc'ed buffer for aloop.  Since it's no hardware buffer, it's
more system-friendly, and you don't need a pre-allocation.
Again, an untested patch is below.


thanks,

Takashi

---
diff --git a/sound/drivers/aloop.c b/sound/drivers/aloop.c
index a0da775..4067f15 100644
--- a/sound/drivers/aloop.c
+++ b/sound/drivers/aloop.c
@@ -575,7 +575,8 @@ static void loopback_runtime_free(struct snd_pcm_runtime *runtime)
 static int loopback_hw_params(struct snd_pcm_substream *substream,
 			      struct snd_pcm_hw_params *params)
 {
-	return snd_pcm_lib_malloc_pages(substream, params_buffer_bytes(params));
+	return snd_pcm_lib_alloc_vmalloc_buffer(substream,
+						params_buffer_bytes(params));
 }
 
 static int loopback_hw_free(struct snd_pcm_substream *substream)
@@ -587,7 +588,7 @@ static int loopback_hw_free(struct snd_pcm_substream *substream)
 	mutex_lock(&dpcm->loopback->cable_lock);
 	cable->valid &= ~(1 << substream->stream);
 	mutex_unlock(&dpcm->loopback->cable_lock);
-	return snd_pcm_lib_free_pages(substream);
+	return snd_pcm_lib_free_vmalloc_buffer(substream);
 }
 
 static unsigned int get_cable_index(struct snd_pcm_substream *substream)
@@ -740,6 +741,8 @@ static struct snd_pcm_ops loopback_playback_ops = {
 	.prepare =	loopback_prepare,
 	.trigger =	loopback_trigger,
 	.pointer =	loopback_pointer,
+	.page =		snd_pcm_lib_get_vmalloc_page,
+	.mmap =		snd_pcm_lib_mmap_vmalloc,
 };
 
 static struct snd_pcm_ops loopback_capture_ops = {
@@ -751,6 +754,8 @@ static struct snd_pcm_ops loopback_capture_ops = {
 	.prepare =	loopback_prepare,
 	.trigger =	loopback_trigger,
 	.pointer =	loopback_pointer,
+	.page =		snd_pcm_lib_get_vmalloc_page,
+	.mmap =		snd_pcm_lib_mmap_vmalloc,
 };
 
 static int __devinit loopback_pcm_new(struct loopback *loopback,
@@ -771,10 +776,6 @@ static int __devinit loopback_pcm_new(struct loopback *loopback,
 	strcpy(pcm->name, "Loopback PCM");
 
 	loopback->pcm[device] = pcm;
-
-	snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_CONTINUOUS,
-			snd_dma_continuous_data(GFP_KERNEL),
-			0, 2 * 1024 * 1024);
 	return 0;
 }