From 68541213720df9bb7904cc1fecab563d424849ae Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Wed, 24 May 2017 18:23:20 +0200 Subject: ALSA: pcm: Direct in-kernel read/write support Now all materials are ready, let's allow the direct in-kernel read/write, i.e. a kernel-space buffer is passed for read or write, instead of the normal user-space buffer. This feature is used by OSS layer and UAC1 driver, for example. The __snd_pcm_lib_xfer() takes in_kernel argument that indicates the in-kernel buffer copy. When this flag is set, another transfer code is used. It's either via copy_kernel PCM ops or the normal memcpy(), depending on the driver setup. As external API, snd_pcm_kernel_read(), *_write() and other variants are provided. That's all. This support is really simple because of the code refactoring until now. Reviewed-by: Takashi Sakamoto Signed-off-by: Takashi Iwai --- sound/core/pcm_lib.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) (limited to 'sound/core/pcm_lib.c') diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c index f31949b20c0d..95b8ef15029f 100644 --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -1994,6 +1994,15 @@ static int default_write_copy(struct snd_pcm_substream *substream, return 0; } +/* default copy_kernel ops for write */ +static int default_write_copy_kernel(struct snd_pcm_substream *substream, + int channel, unsigned long hwoff, + void *buf, unsigned long bytes) +{ + memcpy(get_dma_ptr(substream->runtime, channel, hwoff), buf, bytes); + return 0; +} + /* fill silence instead of copy data; called as a transfer helper * from __snd_pcm_lib_write() or directly from noninterleaved_copy() when * a NULL buffer is passed @@ -2027,6 +2036,15 @@ static int default_read_copy(struct snd_pcm_substream *substream, return 0; } +/* default copy_kernel ops for read */ +static int default_read_copy_kernel(struct snd_pcm_substream *substream, + int channel, unsigned long hwoff, + void *buf, unsigned long bytes) +{ + memcpy(buf, get_dma_ptr(substream->runtime, channel, hwoff), bytes); + return 0; +} + /* call transfer function with the converted pointers and sizes; * for interleaved mode, it's one shot for all samples */ @@ -2126,7 +2144,7 @@ static int pcm_accessible_state(struct snd_pcm_runtime *runtime) /* the common loop for read/write data */ snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream, void *data, bool interleaved, - snd_pcm_uframes_t size) + snd_pcm_uframes_t size, bool in_kernel) { struct snd_pcm_runtime *runtime = substream->runtime; snd_pcm_uframes_t xfer = 0; @@ -2159,6 +2177,12 @@ snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream, transfer = fill_silence; else return -EINVAL; + } else if (in_kernel) { + if (substream->ops->copy_kernel) + transfer = substream->ops->copy_kernel; + else + transfer = is_playback ? + default_write_copy_kernel : default_read_copy_kernel; } else { if (substream->ops->copy_user) transfer = (pcm_transfer_f)substream->ops->copy_user; -- cgit v1.2.3