[alsa-devel] [PATCH] ALSA: Constify the snd_pcm_substream struct ops field

[Lars-Peter Clausen]

The ops field of the snd_pcm_substream struct is never modified inside the ALSA
core. Making it const allows drivers to declare their snd_pcm_ops struct as
const.

Signed-off-by: Lars-Peter Clausen <lars at metafoo.de>
---
 include/sound/pcm.h  | 5 +++--
 sound/core/pcm_lib.c | 3 ++-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index b48792f..84b10f9 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -384,7 +384,7 @@ struct snd_pcm_substream {
 	unsigned int dma_buf_id;
 	size_t dma_max;
 	/* -- hardware operations -- */
-	struct snd_pcm_ops *ops;
+	const struct snd_pcm_ops *ops;
 	/* -- runtime information -- */
 	struct snd_pcm_runtime *runtime;
         /* -- timer section -- */
@@ -871,7 +871,8 @@ const unsigned char *snd_pcm_format_silence_64(snd_pcm_format_t format);
 int snd_pcm_format_set_silence(snd_pcm_format_t format, void *buf, unsigned int frames);
 snd_pcm_format_t snd_pcm_build_linear_format(int width, int unsigned, int big_endian);
 
-void snd_pcm_set_ops(struct snd_pcm * pcm, int direction, struct snd_pcm_ops *ops);
+void snd_pcm_set_ops(struct snd_pcm * pcm, int direction,
+		     const struct snd_pcm_ops *ops);
 void snd_pcm_set_sync(struct snd_pcm_substream *substream);
 int snd_pcm_lib_interleave_len(struct snd_pcm_substream *substream);
 int snd_pcm_lib_ioctl(struct snd_pcm_substream *substream,
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index 41b3dfe..82bb029 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -568,7 +568,8 @@ int snd_pcm_update_hw_ptr(struct snd_pcm_substream *substream)
  *
  * Sets the given PCM operators to the pcm instance.
  */
-void snd_pcm_set_ops(struct snd_pcm *pcm, int direction, struct snd_pcm_ops *ops)
+void snd_pcm_set_ops(struct snd_pcm *pcm, int direction,
+		     const struct snd_pcm_ops *ops)
 {
 	struct snd_pcm_str *stream = &pcm->streams[direction];
 	struct snd_pcm_substream *substream;
-- 
1.8.0