Commit 68541213 authored by Takashi Iwai's avatar Takashi Iwai
Browse files

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: default avatarTakashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent a9cd29e7

include/sound/pcm.h

+33 −5
Original line number Diff line number Diff line
@@ -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);

sound/core/pcm_lib.c

+25 −1
Original line number Diff line number Diff line
@@ -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;

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