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ALSA: pcm: Direct in-kernel read/write support

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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 <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2017-05-24 18:23:20 +02:00
parent a9cd29e799
commit 6854121372
2 changed files with 58 additions and 6 deletions
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38
include/sound/pcm.h
View File

@ -1074,34 +1074,62 @@ int snd_pcm_lib_ioctl(struct snd_pcm_substream *substream,
void snd_pcm_period_elapsed(struct snd_pcm_substream *substream);
snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream,
void *buf, bool interleaved,
snd_pcm_uframes_t frames);
snd_pcm_uframes_t frames, bool in_kernel);
static inline snd_pcm_sframes_t
snd_pcm_lib_write(struct snd_pcm_substream *substream,
const void __user *buf, snd_pcm_uframes_t frames)
{
return __snd_pcm_lib_xfer(substream, (void *)buf, true, frames);
return __snd_pcm_lib_xfer(substream, (void *)buf, true, frames, false);
}
static inline snd_pcm_sframes_t
snd_pcm_lib_read(struct snd_pcm_substream *substream,
void __user *buf, snd_pcm_uframes_t frames)
{
return __snd_pcm_lib_xfer(substream, (void *)buf, true, frames);
return __snd_pcm_lib_xfer(substream, (void *)buf, true, frames, false);
}
static inline snd_pcm_sframes_t
snd_pcm_lib_writev(struct snd_pcm_substream *substream,
void __user **bufs, snd_pcm_uframes_t frames)
{
return __snd_pcm_lib_xfer(substream, (void *)bufs, false, frames);
return __snd_pcm_lib_xfer(substream, (void *)bufs, false, frames, false);
}
static inline snd_pcm_sframes_t
snd_pcm_lib_readv(struct snd_pcm_substream *substream,
void __user **bufs, snd_pcm_uframes_t frames)
{
return __snd_pcm_lib_xfer(substream, (void *)bufs, false, frames);
return __snd_pcm_lib_xfer(substream, (void *)bufs, false, frames, false);
}
static inline snd_pcm_sframes_t
snd_pcm_kernel_write(struct snd_pcm_substream *substream,
const void *buf, snd_pcm_uframes_t frames)
{
return __snd_pcm_lib_xfer(substream, (void *)buf, true, frames, true);
}
static inline snd_pcm_sframes_t
snd_pcm_kernel_read(struct snd_pcm_substream *substream,
void *buf, snd_pcm_uframes_t frames)
{
return __snd_pcm_lib_xfer(substream, buf, true, frames, true);
}
static inline snd_pcm_sframes_t
snd_pcm_kernel_writev(struct snd_pcm_substream *substream,
void **bufs, snd_pcm_uframes_t frames)
{
return __snd_pcm_lib_xfer(substream, bufs, false, frames, true);
}
static inline snd_pcm_sframes_t
snd_pcm_kernel_readv(struct snd_pcm_substream *substream,
void **bufs, snd_pcm_uframes_t frames)
{
return __snd_pcm_lib_xfer(substream, bufs, false, frames, true);
}
int snd_pcm_limit_hw_rates(struct snd_pcm_runtime *runtime);

26
sound/core/pcm_lib.c
View File

@ -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;