From a68c4d11336610dc348620766119db09675707c2 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Fri, 4 Sep 2009 12:19:36 +0200 Subject: [PATCH] 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 --- .../sound/alsa/ALSA-Configuration.txt | 7 ++ sound/drivers/dummy.c | 106 ++++++++++++++++-- 2 files changed, 105 insertions(+), 8 deletions(-) diff --git a/Documentation/sound/alsa/ALSA-Configuration.txt b/Documentation/sound/alsa/ALSA-Configuration.txt index bb488b575def..ea16e7d184a4 100644 --- a/Documentation/sound/alsa/ALSA-Configuration.txt +++ b/Documentation/sound/alsa/ALSA-Configuration.txt @@ -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 diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c index e8e29bfb85ec..2ee6c8ebe25a 100644 --- a/sound/drivers/dummy.c +++ b/sound/drivers/dummy.c @@ -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; -- 2.20.1