ALSA: pcm: Build OSS writev/readv helpers conditionally

The snd_pcm_oss_writev3() and snd_pcm_oss_readv3() are used only in
io.c with CONFIG_SND_PCM_OSS_PLUGINS=y. Add an ifdef to reduce the
build of these functions.

Along with it, since they are called always for in-kernel copy, reduce
the argument and call snd_pcm_kernel_writev() and *_readv() directly
instead.

Reviewed-by: Takashi Sakamoto <[e-mail]>
Signed-off-by: Takashi Iwai <[e-mail]>

sound/core/oss/io.c

···
 #include "pcm_plugin.h"
 
 #define pcm_write(plug,buf,count) snd_pcm_oss_write3(plug,buf,count,1)
-#define pcm_writev(plug,vec,count) snd_pcm_oss_writev3(plug,vec,count,1)
+#define pcm_writev(plug,vec,count) snd_pcm_oss_writev3(plug,vec,count)
 #define pcm_read(plug,buf,count) snd_pcm_oss_read3(plug,buf,count,1)
-#define pcm_readv(plug,vec,count) snd_pcm_oss_readv3(plug,vec,count,1)
+#define pcm_readv(plug,vec,count) snd_pcm_oss_readv3(plug,vec,count)
 
 /*
  *  Basic io plugin

sound/core/oss/pcm_oss.c

···
 	return ret;
 }
 
-snd_pcm_sframes_t snd_pcm_oss_writev3(struct snd_pcm_substream *substream, void **bufs, snd_pcm_uframes_t frames, int in_kernel)
+#ifdef CONFIG_SND_PCM_OSS_PLUGINS
+snd_pcm_sframes_t snd_pcm_oss_writev3(struct snd_pcm_substream *substream, void **bufs, snd_pcm_uframes_t frames)
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	int ret;
···
 			if (ret < 0)
 				break;
 		}
-		ret = __snd_pcm_lib_xfer(substream, bufs, false, frames,
-					 in_kernel);
+		ret = snd_pcm_kernel_writev(substream, bufs, frames);
 		if (ret != -EPIPE && ret != -ESTRPIPE)
 			break;
 
···
 	return ret;
 }
 	
-snd_pcm_sframes_t snd_pcm_oss_readv3(struct snd_pcm_substream *substream, void **bufs, snd_pcm_uframes_t frames, int in_kernel)
+snd_pcm_sframes_t snd_pcm_oss_readv3(struct snd_pcm_substream *substream, void **bufs, snd_pcm_uframes_t frames)
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	int ret;
···
 			if (ret < 0)
 				break;
 		}
-		ret = __snd_pcm_lib_xfer(substream, bufs, false, frames,
-					 in_kernel);
+		ret = snd_pcm_kernel_readv(substream, bufs, frames);
 		if (ret != -EPIPE && ret != -ESTRPIPE)
 			break;
 	}
 	return ret;
 }
+#endif /* CONFIG_SND_PCM_OSS_PLUGINS */
 
 static ssize_t snd_pcm_oss_write2(struct snd_pcm_substream *substream, const char *buf, size_t bytes, int in_kernel)
 {

sound/core/oss/pcm_plugin.h

···
 snd_pcm_sframes_t snd_pcm_oss_read3(struct snd_pcm_substream *substream,
 				    char *ptr, snd_pcm_uframes_t size, int in_kernel);
 snd_pcm_sframes_t snd_pcm_oss_writev3(struct snd_pcm_substream *substream,
-				      void **bufs, snd_pcm_uframes_t frames,
-				      int in_kernel);
+				      void **bufs, snd_pcm_uframes_t frames);
 snd_pcm_sframes_t snd_pcm_oss_readv3(struct snd_pcm_substream *substream,
-				     void **bufs, snd_pcm_uframes_t frames,
-				     int in_kernel);
+				     void **bufs, snd_pcm_uframes_t frames);
 
 #else