ALSA: dummy - Fake buffer allocations
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>
diff --git a/Documentation/sound/alsa/ALSA-Configuration.txt b/Documentation/sound/alsa/ALSA-Configuration.txt
index bb488b5..ea16e7d 100644
--- a/Documentation/sound/alsa/ALSA-Configuration.txt
+++ b/Documentation/sound/alsa/ALSA-Configuration.txt
@@ -518,6 +518,7 @@
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 @@
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
diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c
index e8e29bf..2ee6c8e 100644
--- a/sound/drivers/dummy.c
+++ b/sound/drivers/dummy.c
@@ -153,6 +153,7 @@
#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_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_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 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 @@
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 @@
.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 @@
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 @@
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 @@
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;