[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>

1 files changed, 55 insertions, 26 deletions

diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index 7b5729c4b21..36d6765618a 100644
--- a/sound/core/pcm_native.c
+++ b/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;