adulau/aha
1
0
Fork 0
mirror of https://github.com/adulau/aha.git synced 2024-12-27 19:26:25 +00:00
Code Issues Projects Releases Packages Wiki Activity

ALSA: dummy - Fake buffer allocations

Browse source 
Instead of allocating the real buffers, use a fake buffer and ignore
read/write in the dummy driver so that we can save the resources.
For mmap, a single page (unique to the direction, though) is reused
to all buffers.

When the app requires to read/write the real buffers, pass fake_buffer=0
module option at loading time.  This will get back to the old behavior.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2009-09-04 12:19:36 +02:00
parent b5d1078173
commit a68c4d1133
2 changed files with 105 additions and 8 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

7
Documentation/sound/alsa/ALSA-Configuration.txt
View file

@ -518,6 +518,7 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.
pcm_substreams - Number of PCM substreams assigned to each PCM
(default = 8, up to 16)
hrtimer - Use hrtimer (=1, default) or system timer (=0)
fake_buffer - Fake buffer allocations (default = 1)
When multiple PCM devices are created, snd-dummy gives different
behavior to each PCM device:
@ -526,6 +527,12 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.
2 = interleaved without mmap
3 = non-interleaved without mmap
As default, snd-dummy drivers doesn't allocate the real buffers
but either ignores read/write or mmap a single dummy page to all
buffer pages, in order to save the resouces. If your apps need
the read/ written buffer data to be consistent, pass fake_buffer=0
option.
The power-management is supported.
Module snd-echo3g

106
sound/drivers/dummy.c
View file

@ -153,6 +153,7 @@ static int pcm_substreams[SNDRV_CARDS] = {[0 ... (SNDRV_CARDS - 1)] = 8};
#ifdef CONFIG_HIGH_RES_TIMERS
static int hrtimer = 1;
#endif
static int fake_buffer = 1;
module_param_array(index, int, NULL, 0444);
MODULE_PARM_DESC(index, "Index value for dummy soundcard.");
@ -166,6 +167,8 @@ module_param_array(pcm_substreams, int, NULL, 0444);
MODULE_PARM_DESC(pcm_substreams, "PCM substreams # (1-16) for dummy driver.");
//module_param_array(midi_devs, int, NULL, 0444);
//MODULE_PARM_DESC(midi_devs, "MIDI devices # (0-2) for dummy driver.");
module_param(fake_buffer, bool, 0444);
MODULE_PARM_DESC(fake_buffer, "Fake buffer allocations.");
#ifdef CONFIG_HIGH_RES_TIMERS
module_param(hrtimer, bool, 0644);
MODULE_PARM_DESC(hrtimer, "Use hrtimer as the timer source.");
@ -481,11 +484,8 @@ static int dummy_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
static int dummy_pcm_prepare(struct snd_pcm_substream *substream)
{
struct snd_pcm_runtime *runtime = substream->runtime;
struct snd_dummy *dummy = snd_pcm_substream_chip(substream);
snd_pcm_format_set_silence(runtime->format, runtime->dma_area,
bytes_to_samples(runtime, runtime->dma_bytes));
return dummy->timer_ops->prepare(substream);
}
@ -518,12 +518,19 @@ static struct snd_pcm_hardware dummy_pcm_hardware = {
static int dummy_pcm_hw_params(struct snd_pcm_substream *substream,
struct snd_pcm_hw_params *hw_params)
{
if (fake_buffer) {
/* runtime->dma_bytes has to be set manually to allow mmap */
substream->runtime->dma_bytes = params_buffer_bytes(hw_params);
return 0;
}
return snd_pcm_lib_malloc_pages(substream,
params_buffer_bytes(hw_params));
}
static int dummy_pcm_hw_free(struct snd_pcm_substream *substream)
{
if (fake_buffer)
return 0;
return snd_pcm_lib_free_pages(substream);
}
@ -570,6 +577,60 @@ static int dummy_pcm_close(struct snd_pcm_substream *substream)
return 0;
}
/*
* dummy buffer handling
*/
static void *dummy_page[2];
static void free_fake_buffer(void)
{
if (fake_buffer) {
int i;
for (i = 0; i < 2; i++)
if (dummy_page[i]) {
free_page((unsigned long)dummy_page[i]);
dummy_page[i] = NULL;
}
}
}
static int alloc_fake_buffer(void)
{
int i;
if (!fake_buffer)
return 0;
for (i = 0; i < 2; i++) {
dummy_page[i] = (void *)get_zeroed_page(GFP_KERNEL);
if (!dummy_page[i]) {
free_fake_buffer();
return -ENOMEM;
}
}
return 0;
}
static int dummy_pcm_copy(struct snd_pcm_substream *substream,
int channel, snd_pcm_uframes_t pos,
void __user *dst, snd_pcm_uframes_t count)
{
return 0; /* do nothing */
}
static int dummy_pcm_silence(struct snd_pcm_substream *substream,
int channel, snd_pcm_uframes_t pos,
snd_pcm_uframes_t count)
{
return 0; /* do nothing */
}
static struct page *dummy_pcm_page(struct snd_pcm_substream *substream,
unsigned long offset)
{
return virt_to_page(dummy_page[substream->stream]); /* the same page */
}
static struct snd_pcm_ops dummy_pcm_ops = {
.open = dummy_pcm_open,
.close = dummy_pcm_close,
@ -581,10 +642,25 @@ static struct snd_pcm_ops dummy_pcm_ops = {
.pointer = dummy_pcm_pointer,
};
static struct snd_pcm_ops dummy_pcm_ops_no_buf = {
.open = dummy_pcm_open,
.close = dummy_pcm_close,
.ioctl = snd_pcm_lib_ioctl,
.hw_params = dummy_pcm_hw_params,
.hw_free = dummy_pcm_hw_free,
.prepare = dummy_pcm_prepare,
.trigger = dummy_pcm_trigger,
.pointer = dummy_pcm_pointer,
.copy = dummy_pcm_copy,
.silence = dummy_pcm_silence,
.page = dummy_pcm_page,
};
static int __devinit snd_card_dummy_pcm(struct snd_dummy *dummy, int device,
int substreams)
{
struct snd_pcm *pcm;
struct snd_pcm_ops *ops;
int err;
err = snd_pcm_new(dummy->card, "Dummy PCM", device,
@ -592,14 +668,21 @@ static int __devinit snd_card_dummy_pcm(struct snd_dummy *dummy, int device,
if (err < 0)
return err;
dummy->pcm = pcm;
snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, &dummy_pcm_ops);
snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, &dummy_pcm_ops);
if (fake_buffer)
ops = &dummy_pcm_ops_no_buf;
else
ops = &dummy_pcm_ops;
snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, ops);
snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, ops);
pcm->private_data = dummy;
pcm->info_flags = 0;
strcpy(pcm->name, "Dummy PCM");
snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_CONTINUOUS,
snd_dma_continuous_data(GFP_KERNEL),
0, 64*1024);
if (!fake_buffer) {
snd_pcm_lib_preallocate_pages_for_all(pcm,
SNDRV_DMA_TYPE_CONTINUOUS,
snd_dma_continuous_data(GFP_KERNEL),
0, 64*1024);
}
return 0;
}
@ -822,6 +905,7 @@ static void snd_dummy_unregister_all(void)
for (i = 0; i < ARRAY_SIZE(devices); ++i)
platform_device_unregister(devices[i]);
platform_driver_unregister(&snd_dummy_driver);
free_fake_buffer();
}
static int __init alsa_card_dummy_init(void)
@ -832,6 +916,12 @@ static int __init alsa_card_dummy_init(void)
if (err < 0)
return err;
err = alloc_fake_buffer();
if (err < 0) {
platform_driver_unregister(&snd_dummy_driver);
return err;
}
cards = 0;
for (i = 0; i < SNDRV_CARDS; i++) {
struct platform_device *device;