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ALSA: pcm: Introduce copy_user, copy_kernel and fill_silence ops

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For supporting the explicit in-kernel copy of PCM buffer data, and
also for further code refactoring, three new PCM ops, copy_user,
copy_kernel and fill_silence, are introduced.  The old copy and
silence ops will be deprecated and removed later once when all callers
are converted.

The copy_kernel ops is the new one, and it's supposed to transfer the
PCM data from the given kernel buffer to the hardware ring-buffer (or
vice-versa depending on the stream direction), while the copy_user ops
is equivalent with the former copy ops, to transfer the data from the
user-space buffer.

The major difference of the new copy_* and fill_silence ops from the
previous ops is that the new ops take bytes instead of frames for size
and position arguments.  It has two merits: first, it allows the
callback implementation often simpler (just call directly memcpy() &
co), and second, it may unify the implementations of both interleaved
and non-interleaved cases, as we'll see in the later patch.

As of this stage, copy_kernel ops isn't referred yet, but only
copy_user is used.

Reviewed-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai
2017-05-10 20:02:35 +02:00
parent 7421a1671a
commit 29d1a873de
3 changed files with 84 additions and 15 deletions
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7
include/sound/pcm.h
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@@ -83,6 +83,13 @@ struct snd_pcm_ops {
void __user *buf, snd_pcm_uframes_t count);
int (*silence)(struct snd_pcm_substream *substream, int channel,
snd_pcm_uframes_t pos, snd_pcm_uframes_t count);
int (*fill_silence)(struct snd_pcm_substream *substream, int channel,
unsigned long pos, unsigned long bytes);
int (*copy_user)(struct snd_pcm_substream *substream, int channel,
unsigned long pos, void __user *buf,
unsigned long bytes);
int (*copy_kernel)(struct snd_pcm_substream *substream, int channel,
unsigned long pos, void *buf, unsigned long bytes);
struct page *(*page)(struct snd_pcm_substream *substream,
unsigned long offset);
int (*mmap)(struct snd_pcm_substream *substream, struct vm_area_struct *vma);