[ALSA] Add O_APPEND flag support to PCM

Added O_APPEND flag support to PCM to enable shared substreams
among multiple processes.  This mechanism is used by dmix and
dsnoop plugins.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

include/sound/asound.h

@@ -137,7 +137,7 @@ enum {
  *                                                                           *
  *****************************************************************************/
 
-#define SNDRV_PCM_VERSION		SNDRV_PROTOCOL_VERSION(2, 0, 7)
+#define SNDRV_PCM_VERSION		SNDRV_PROTOCOL_VERSION(2, 0, 8)
 
 typedef unsigned long snd_pcm_uframes_t;
 typedef signed long snd_pcm_sframes_t;

include/sound/pcm.h

@@ -368,7 +368,8 @@ struct snd_pcm_substream {
 	struct snd_pcm_group *group;		/* pointer to current group */
 	/* -- assigned files -- */
 	void *file;
-	struct file *ffile;
+	int ref_count;
+	unsigned int f_flags;
 	void (*pcm_release)(struct snd_pcm_substream *);
 #if defined(CONFIG_SND_PCM_OSS) || defined(CONFIG_SND_PCM_OSS_MODULE)
 	/* -- OSS things -- */
@@ -387,7 +388,7 @@ struct snd_pcm_substream {
 	unsigned int hw_opened: 1;
 };
 
-#define SUBSTREAM_BUSY(substream) ((substream)->file != NULL)
+#define SUBSTREAM_BUSY(substream) ((substream)->ref_count > 0)
 
 
 struct snd_pcm_str {

sound/core/oss/pcm_oss.c

@@ -1331,7 +1331,7 @@ static ssize_t snd_pcm_oss_write1(struct snd_pcm_substream *substream, const cha
 				if (runtime->oss.period_ptr == 0 ||
 				    runtime->oss.period_ptr == runtime->oss.buffer_used)
 					runtime->oss.buffer_used = 0;
-				else if ((substream->ffile->f_flags & O_NONBLOCK) != 0)
+				else if ((substream->f_flags & O_NONBLOCK) != 0)
 					return xfer > 0 ? xfer : -EAGAIN;
 			}
 		} else {
@@ -1344,7 +1344,7 @@ static ssize_t snd_pcm_oss_write1(struct snd_pcm_substream *substream, const cha
 			buf += tmp;
 			bytes -= tmp;
 			xfer += tmp;
-			if ((substream->ffile->f_flags & O_NONBLOCK) != 0 &&
+			if ((substream->f_flags & O_NONBLOCK) != 0 &&
 			    tmp != runtime->oss.period_bytes)
 				break;
 		}
@@ -1582,10 +1582,10 @@ static int snd_pcm_oss_sync(struct snd_pcm_oss_file *pcm_oss_file)
 		 * finish sync: drain the buffer
 		 */
 	      __direct:
-		saved_f_flags = substream->ffile->f_flags;
-		substream->ffile->f_flags &= ~O_NONBLOCK;
+		saved_f_flags = substream->f_flags;
+		substream->f_flags &= ~O_NONBLOCK;
 		err = snd_pcm_kernel_ioctl(substream, SNDRV_PCM_IOCTL_DRAIN, NULL);
-		substream->ffile->f_flags = saved_f_flags;
+		substream->f_flags = saved_f_flags;
 		if (err < 0)
 			return err;
 		runtime->oss.prepare = 1;
@@ -2164,9 +2164,9 @@ static void snd_pcm_oss_init_substream(struct snd_pcm_substream *substream,
 	substream->oss.oss = 1;
 	substream->oss.setup = *setup;
 	if (setup->nonblock)
-		substream->ffile->f_flags |= O_NONBLOCK;
+		substream->f_flags |= O_NONBLOCK;
 	else if (setup->block)
-		substream->ffile->f_flags &= ~O_NONBLOCK;
+		substream->f_flags &= ~O_NONBLOCK;
 	runtime = substream->runtime;
 	runtime->oss.params = 1;
 	runtime->oss.trigger = 1;
@@ -2223,6 +2223,7 @@ static int snd_pcm_oss_open_file(struct file *file,
 	    (pcm->info_flags & SNDRV_PCM_INFO_HALF_DUPLEX))
 		f_mode = FMODE_WRITE;
 
+	file->f_flags &= ~O_APPEND;
 	for (idx = 0; idx < 2; idx++) {
 		if (setup[idx].disable)
 			continue;
@@ -2540,6 +2541,7 @@ static ssize_t snd_pcm_oss_read(struct file *file, char __user *buf, size_t coun
 	substream = pcm_oss_file->streams[SNDRV_PCM_STREAM_CAPTURE];
 	if (substream == NULL)
 		return -ENXIO;
+	substream->f_flags = file->f_flags & O_NONBLOCK;
 #ifndef OSS_DEBUG
 	return snd_pcm_oss_read1(substream, buf, count);
 #else
@@ -2561,6 +2563,7 @@ static ssize_t snd_pcm_oss_write(struct file *file, const char __user *buf, size
 	substream = pcm_oss_file->streams[SNDRV_PCM_STREAM_PLAYBACK];
 	if (substream == NULL)
 		return -ENXIO;
+	substream->f_flags = file->f_flags & O_NONBLOCK;
 	result = snd_pcm_oss_write1(substream, buf, count);
 #ifdef OSS_DEBUG
 	printk("pcm_oss: write %li bytes (wrote %li bytes)\n", (long)count, (long)result);

sound/core/pcm.c

@@ -829,6 +829,26 @@ int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream,
 		return -EINVAL;
 	}
 
+	if (file->f_flags & O_APPEND) {
+		if (prefer_subdevice < 0) {
+			if (pstr->substream_count > 1)
+				return -EINVAL; /* must be unique */
+			substream = pstr->substream;
+		} else {
+			for (substream = pstr->substream; substream;
+			     substream = substream->next)
+				if (substream->number == prefer_subdevice)
+					break;
+		}
+		if (! substream)
+			return -ENODEV;
+		if (! SUBSTREAM_BUSY(substream))
+			return -EBADFD;
+		substream->ref_count++;
+		*rsubstream = substream;
+		return 0;
+	}
+
 	if (prefer_subdevice >= 0) {
 		for (substream = pstr->substream; substream; substream = substream->next)
 			if (!SUBSTREAM_BUSY(substream) && substream->number == prefer_subdevice)
@@ -873,7 +893,8 @@ int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream,
 
 	substream->runtime = runtime;
 	substream->private_data = pcm->private_data;
-	substream->ffile = file;
+	substream->ref_count = 1;
+	substream->f_flags = file->f_flags;
 	pstr->substream_opened++;
 	*rsubstream = substream;
 	return 0;
@@ -882,7 +903,7 @@ int snd_pcm_attach_substream(struct snd_pcm *pcm, int stream,
 void snd_pcm_detach_substream(struct snd_pcm_substream *substream)
 {
 	struct snd_pcm_runtime *runtime;
-	substream->file = NULL;
+
 	runtime = substream->runtime;
 	snd_assert(runtime != NULL, return);
 	if (runtime->private_free != NULL)

sound/core/pcm_compat.c

@@ -497,9 +497,9 @@ static long snd_pcm_ioctl_compat(struct file *file, unsigned int cmd, unsigned l
 	case SNDRV_PCM_IOCTL_LINK:
 	case SNDRV_PCM_IOCTL_UNLINK:
 		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
-			return snd_pcm_playback_ioctl1(substream, cmd, argp);
+			return snd_pcm_playback_ioctl1(file, substream, cmd, argp);
 		else
-			return snd_pcm_capture_ioctl1(substream, cmd, argp);
+			return snd_pcm_capture_ioctl1(file, substream, cmd, argp);
 	case SNDRV_PCM_IOCTL_HW_REFINE32:
 		return snd_pcm_ioctl_hw_params_compat(substream, 1, argp);
 	case SNDRV_PCM_IOCTL_HW_PARAMS32:

sound/core/pcm_lib.c

@@ -1782,7 +1782,7 @@ snd_pcm_sframes_t snd_pcm_lib_write(struct snd_pcm_substream *substream, const v
 	if (runtime->status->state == SNDRV_PCM_STATE_OPEN)
 		return -EBADFD;
 
-	nonblock = !!(substream->ffile->f_flags & O_NONBLOCK);
+	nonblock = !!(substream->f_flags & O_NONBLOCK);
 
 	if (runtime->access != SNDRV_PCM_ACCESS_RW_INTERLEAVED &&
 	    runtime->channels > 1)
@@ -1847,7 +1847,7 @@ snd_pcm_sframes_t snd_pcm_lib_writev(struct snd_pcm_substream *substream,
 	if (runtime->status->state == SNDRV_PCM_STATE_OPEN)
 		return -EBADFD;
 
-	nonblock = !!(substream->ffile->f_flags & O_NONBLOCK);
+	nonblock = !!(substream->f_flags & O_NONBLOCK);
 
 	if (runtime->access != SNDRV_PCM_ACCESS_RW_NONINTERLEAVED)
 		return -EINVAL;
@@ -2059,7 +2059,7 @@ snd_pcm_sframes_t snd_pcm_lib_read(struct snd_pcm_substream *substream, void __u
 	if (runtime->status->state == SNDRV_PCM_STATE_OPEN)
 		return -EBADFD;
 
-	nonblock = !!(substream->ffile->f_flags & O_NONBLOCK);
+	nonblock = !!(substream->f_flags & O_NONBLOCK);
 	if (runtime->access != SNDRV_PCM_ACCESS_RW_INTERLEAVED)
 		return -EINVAL;
 	return snd_pcm_lib_read1(substream, (unsigned long)buf, size, nonblock, snd_pcm_lib_read_transfer);
@@ -2118,7 +2118,7 @@ snd_pcm_sframes_t snd_pcm_lib_readv(struct snd_pcm_substream *substream,
 	if (runtime->status->state == SNDRV_PCM_STATE_OPEN)
 		return -EBADFD;
 
-	nonblock = !!(substream->ffile->f_flags & O_NONBLOCK);
+	nonblock = !!(substream->f_flags & O_NONBLOCK);
 	if (runtime->access != SNDRV_PCM_ACCESS_RW_NONINTERLEAVED)
 		return -EINVAL;
 	return snd_pcm_lib_read1(substream, (unsigned long)bufs, frames, nonblock, snd_pcm_lib_readv_transfer);

sound/core/pcm_native.c

@@ -1284,13 +1284,16 @@ static int snd_pcm_reset(struct snd_pcm_substream *substream)
 /*
  * prepare ioctl
  */
-static int snd_pcm_pre_prepare(struct snd_pcm_substream *substream, int state)
+/* we use the second argument for updating f_flags */
+static int snd_pcm_pre_prepare(struct snd_pcm_substream *substream,
+			       int f_flags)
 {
 	struct snd_pcm_runtime *runtime = substream->runtime;
 	if (runtime->status->state == SNDRV_PCM_STATE_OPEN)
 		return -EBADFD;
 	if (snd_pcm_running(substream))
 		return -EBUSY;
+	substream->f_flags = f_flags;
 	return 0;
 }
 
@@ -1319,17 +1322,26 @@ static struct action_ops snd_pcm_action_prepare = {
 /**
  * snd_pcm_prepare
  * @substream: the PCM substream instance
+ * @file: file to refer f_flags
  *
  * Prepare the PCM substream to be triggerable.
  */
-static int snd_pcm_prepare(struct snd_pcm_substream *substream)
+static int snd_pcm_prepare(struct snd_pcm_substream *substream,
+			   struct file *file)
 {
 	int res;
 	struct snd_card *card = substream->pcm->card;
+	int f_flags;
+
+	if (file)
+		f_flags = file->f_flags;
+	else
+		f_flags = substream->f_flags;
 
 	snd_power_lock(card);
 	if ((res = snd_power_wait(card, SNDRV_CTL_POWER_D0)) >= 0)
-		res = snd_pcm_action_nonatomic(&snd_pcm_action_prepare, substream, 0);
+		res = snd_pcm_action_nonatomic(&snd_pcm_action_prepare,
+					       substream, f_flags);
 	snd_power_unlock(card);
 	return res;
 }
@@ -1340,7 +1352,7 @@ static int snd_pcm_prepare(struct snd_pcm_substream *substream)
 
 static int snd_pcm_pre_drain_init(struct snd_pcm_substream *substream, int state)
 {
-	if (substream->ffile->f_flags & O_NONBLOCK)
+	if (substream->f_flags & O_NONBLOCK)
 		return -EAGAIN;
 	substream->runtime->trigger_master = substream;
 	return 0;
@@ -2015,6 +2027,10 @@ static void pcm_release_private(struct snd_pcm_substream *substream)
 
 void snd_pcm_release_substream(struct snd_pcm_substream *substream)
 {
+	substream->ref_count--;
+	if (substream->ref_count > 0)
+		return;
+
 	snd_pcm_drop(substream);
 	if (substream->hw_opened) {
 		if (substream->ops->hw_free != NULL)
@@ -2041,6 +2057,11 @@ int snd_pcm_open_substream(struct snd_pcm *pcm, int stream,
 	err = snd_pcm_attach_substream(pcm, stream, file, &substream);
 	if (err < 0)
 		return err;
+	if (substream->ref_count > 1) {
+		*rsubstream = substream;
+		return 0;
+	}
+
 	substream->no_mmap_ctrl = 0;
 	err = snd_pcm_hw_constraints_init(substream);
 	if (err < 0) {
@@ -2086,17 +2107,20 @@ static int snd_pcm_open_file(struct file *file,
 	if (err < 0)
 		return err;
 
-	pcm_file = kzalloc(sizeof(*pcm_file), GFP_KERNEL);
-	if (pcm_file == NULL) {
-		snd_pcm_release_substream(substream);
-		return -ENOMEM;
+	if (substream->ref_count > 1)
+		pcm_file = substream->file;
+	else {
+		pcm_file = kzalloc(sizeof(*pcm_file), GFP_KERNEL);
+		if (pcm_file == NULL) {
+			snd_pcm_release_substream(substream);
+			return -ENOMEM;
+		}
+		str = substream->pstr;
+		substream->file = pcm_file;
+		substream->pcm_release = pcm_release_private;
+		pcm_file->substream = substream;
+		snd_pcm_add_file(str, pcm_file);
 	}
-	str = substream->pstr;
-	substream->file = pcm_file;
-	substream->pcm_release = pcm_release_private;
-	pcm_file->substream = substream;
-	snd_pcm_add_file(str, pcm_file);
-
 	file->private_data = pcm_file;
 	*rpcm_file = pcm_file;
 	return 0;
@@ -2506,7 +2530,8 @@ static int snd_pcm_sync_ptr(struct snd_pcm_substream *substream,
 	return 0;
 }
 		
-static int snd_pcm_common_ioctl1(struct snd_pcm_substream *substream,
+static int snd_pcm_common_ioctl1(struct file *file,
+				 struct snd_pcm_substream *substream,
 				 unsigned int cmd, void __user *arg)
 {
 	snd_assert(substream != NULL, return -ENXIO);
@@ -2531,7 +2556,7 @@ static int snd_pcm_common_ioctl1(struct snd_pcm_substream *substream,
 	case SNDRV_PCM_IOCTL_CHANNEL_INFO:
 		return snd_pcm_channel_info_user(substream, arg);
 	case SNDRV_PCM_IOCTL_PREPARE:
-		return snd_pcm_prepare(substream);
+		return snd_pcm_prepare(substream, file);
 	case SNDRV_PCM_IOCTL_RESET:
 		return snd_pcm_reset(substream);
 	case SNDRV_PCM_IOCTL_START:
@@ -2573,7 +2598,8 @@ static int snd_pcm_common_ioctl1(struct snd_pcm_substream *substream,
 	return -ENOTTY;
 }
 
-static int snd_pcm_playback_ioctl1(struct snd_pcm_substream *substream,
+static int snd_pcm_playback_ioctl1(struct file *file,
+				   struct snd_pcm_substream *substream,
 				   unsigned int cmd, void __user *arg)
 {
 	snd_assert(substream != NULL, return -ENXIO);
@@ -2649,10 +2675,11 @@ static int snd_pcm_playback_ioctl1(struct snd_pcm_substream *substream,
 		return result < 0 ? result : 0;
 	}
 	}
-	return snd_pcm_common_ioctl1(substream, cmd, arg);
+	return snd_pcm_common_ioctl1(file, substream, cmd, arg);
 }
 
-static int snd_pcm_capture_ioctl1(struct snd_pcm_substream *substream,
+static int snd_pcm_capture_ioctl1(struct file *file,
+				  struct snd_pcm_substream *substream,
 				  unsigned int cmd, void __user *arg)
 {
 	snd_assert(substream != NULL, return -ENXIO);
@@ -2728,7 +2755,7 @@ static int snd_pcm_capture_ioctl1(struct snd_pcm_substream *substream,
 		return result < 0 ? result : 0;
 	}
 	}
-	return snd_pcm_common_ioctl1(substream, cmd, arg);
+	return snd_pcm_common_ioctl1(file, substream, cmd, arg);
 }
 
 static long snd_pcm_playback_ioctl(struct file *file, unsigned int cmd,
@@ -2741,7 +2768,8 @@ static long snd_pcm_playback_ioctl(struct file *file, unsigned int cmd,
 	if (((cmd >> 8) & 0xff) != 'A')
 		return -ENOTTY;
 
-	return snd_pcm_playback_ioctl1(pcm_file->substream, cmd, (void __user *)arg);
+	return snd_pcm_playback_ioctl1(file, pcm_file->substream, cmd,
+				       (void __user *)arg);
 }
 
 static long snd_pcm_capture_ioctl(struct file *file, unsigned int cmd,
@@ -2754,7 +2782,8 @@ static long snd_pcm_capture_ioctl(struct file *file, unsigned int cmd,
 	if (((cmd >> 8) & 0xff) != 'A')
 		return -ENOTTY;
 
-	return snd_pcm_capture_ioctl1(pcm_file->substream, cmd, (void __user *)arg);
+	return snd_pcm_capture_ioctl1(file, pcm_file->substream, cmd,
+				      (void __user *)arg);
 }
 
 int snd_pcm_kernel_ioctl(struct snd_pcm_substream *substream,
@@ -2766,12 +2795,12 @@ int snd_pcm_kernel_ioctl(struct snd_pcm_substream *substream,
 	fs = snd_enter_user();
 	switch (substream->stream) {
 	case SNDRV_PCM_STREAM_PLAYBACK:
-		result = snd_pcm_playback_ioctl1(substream,
-						 cmd, (void __user *)arg);
+		result = snd_pcm_playback_ioctl1(NULL, substream, cmd,
+						 (void __user *)arg);
 		break;
 	case SNDRV_PCM_STREAM_CAPTURE:
-		result = snd_pcm_capture_ioctl1(substream,
-						cmd, (void __user *)arg);
+		result = snd_pcm_capture_ioctl1(NULL, substream, cmd,
+						(void __user *)arg);
 		break;
 	default:
 		result = -EINVAL;

sound/usb/usx2y/usx2yhwdeppcm.c

@@ -632,7 +632,7 @@ static int usX2Y_pcms_lock_check(struct snd_card *card)
 		for (s = 0; s < 2; ++s) {
 			struct snd_pcm_substream *substream;
 			substream = pcm->streams[s].substream;
-			if (substream && substream->ffile != NULL)
+			if (SUBSTREAM_BUSY(substream))
 				err = -EBUSY;
 		}
 	}