ALSA: compress_core: Deconstify copy callback buffer

The buffer passed to the copy callback should not be const because the
copy callback can be used for capture and playback.

Change-Id: I20674598b00bf933a0fe08eb77c122df6cdf3369
Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Richard Fitzgerald <rf@opensource.wolfsonmicro.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Eric Laurent <elaurent@google.com>
Signed-off-by: Krishnankutty Kolathappilly <kkolat@codeaurora.org>

include/sound/compress_driver.h

@@ -123,7 +123,7 @@ struct snd_compr_ops {
 	int (*trigger)(struct snd_compr_stream *stream, int cmd);
 	int (*pointer)(struct snd_compr_stream *stream,
 			struct snd_compr_tstamp *tstamp);
-	int (*copy)(struct snd_compr_stream *stream, const char __user *buf,
+	int (*copy)(struct snd_compr_stream *stream, char __user *buf,
 		       size_t count);
 	int (*mmap)(struct snd_compr_stream *stream,
 			struct vm_area_struct *vma);

sound/core/compress_offload.c

@@ -279,10 +279,12 @@ static ssize_t snd_compr_write(struct file *f, const char __user *buf,
 	if (avail > count)
 		avail = count;
 
-	if (stream->ops->copy)
-		retval = stream->ops->copy(stream, buf, avail);
-	else
+	if (stream->ops->copy) {
+		char __user* cbuf = (char __user*)buf;
+		retval = stream->ops->copy(stream, cbuf, avail);
+	} else {
 		retval = snd_compr_write_data(stream, buf, avail);
+	}
 	if (retval > 0)
 		stream->runtime->total_bytes_available += retval;
 

sound/soc/soc-compress.c

@@ -584,7 +584,7 @@ static int soc_compr_pointer(struct snd_compr_stream *cstream,
 }
 
 static int soc_compr_copy(struct snd_compr_stream *cstream,
-			  const char __user *buf, size_t count)
+			  char __user *buf, size_t count)
 {
 	struct snd_soc_pcm_runtime *rtd = cstream->private_data;
 	struct snd_soc_platform *platform = rtd->platform;