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authorTakashi Iwai <tiwai@suse.de>2017-05-24 18:23:20 +0200
committerTakashi Iwai <tiwai@suse.de>2017-06-02 19:38:24 +0200
commit68541213720df9bb7904cc1fecab563d424849ae (patch)
treee8d3036ac6fe85d3e0b43bfa0dec7f16ee315127 /sound/core/pcm_lib.c
parenta9cd29e79965f0f769d13edcf2e9adb389698e7b (diff)
downloadlinux-68541213720df9bb7904cc1fecab563d424849ae.tar.bz2
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 <o-takashi@sakamocchi.jp> Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/core/pcm_lib.c')
-rw-r--r--sound/core/pcm_lib.c26
1 files changed, 25 insertions, 1 deletions
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;