[alsa-devel] [PATCH] Provide sequencer sound card number / PID via alsa-lib

[Martin Koegler]

From: Martin Koegler <martin.koegler at chello.at>

rawmidi devices expose the card number via IOCTLs, which allows to
find the corresponding device in sysfs.

The sequencer provides no identifing data. Chromium works around this
issue by scanning rawmidi as well as sequencer devices and matching
them by using assumtions, how the kernel register sequencer devices.

This changes adds support for exposing the card number for kernel clients
as well as the PID for user client.

It supports kernels with and without the required support.

Signed-off-by: Martin Koegler <martin.koegler at chello.at>
---
 include/seq.h              |  2 ++
 include/sound/asequencer.h |  6 ++++--
 src/seq/seq.c              | 26 ++++++++++++++++++++++++++
 src/seq/seq_hw.c           | 12 +++++++++++-
 4 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/include/seq.h b/include/seq.h
index 9576822..d05940e 100644
--- a/include/seq.h
+++ b/include/seq.h
@@ -143,6 +143,8 @@ snd_seq_client_type_t snd_seq_client_info_get_type(const snd_seq_client_info_t *
 const char *snd_seq_client_info_get_name(snd_seq_client_info_t *info);
 int snd_seq_client_info_get_broadcast_filter(const snd_seq_client_info_t *info);
 int snd_seq_client_info_get_error_bounce(const snd_seq_client_info_t *info);
+int snd_seq_client_info_get_card(const snd_seq_client_info_t *info);
+int snd_seq_client_info_get_pid(const snd_seq_client_info_t *info);
 const unsigned char *snd_seq_client_info_get_event_filter(const snd_seq_client_info_t *info);
 int snd_seq_client_info_get_num_ports(const snd_seq_client_info_t *info);
 int snd_seq_client_info_get_event_lost(const snd_seq_client_info_t *info);
diff --git a/include/sound/asequencer.h b/include/sound/asequencer.h
index 09c8a00..3ac70fd 100644
--- a/include/sound/asequencer.h
+++ b/include/sound/asequencer.h
@@ -24,7 +24,7 @@
 
 
 /** version of the sequencer */
-#define SNDRV_SEQ_VERSION SNDRV_PROTOCOL_VERSION (1, 0, 1)
+#define SNDRV_SEQ_VERSION SNDRV_PROTOCOL_VERSION (1, 0, 2)
 
 /**
  * definition of sequencer event types
@@ -356,7 +356,9 @@ struct snd_seq_client_info {
 	unsigned char event_filter[32];	/* event filter bitmap */
 	int num_ports;			/* RO: number of ports */
 	int event_lost;			/* number of lost events */
-	char reserved[64];		/* for future use */
+	int card;			/* RO: card number[kernel] */
+	int pid;			/* RO: pid[user] */
+	char reserved[56];		/* for future use */
 };
 
 
diff --git a/src/seq/seq.c b/src/seq/seq.c
index 620ca3f..4405e68 100644
--- a/src/seq/seq.c
+++ b/src/seq/seq.c
@@ -1522,6 +1522,32 @@ int snd_seq_client_info_get_error_bounce(const snd_seq_client_info_t *info)
 }
 
 /**
+ * \brief Get the sound card number.
+ * \param info client_info container
+ * \return card number or -1 if value is not available.
+ *
+ * Only available for SND_SEQ_KERNEL_CLIENT clients.
+ */
+int snd_seq_client_info_get_card(const snd_seq_client_info_t *info)
+{
+	assert(info);
+	return info->card;
+}
+
+/**
+ * \brief Get the owning PID.
+ * \param info client_info container
+ * \return pid or -1 if value is not available.
+ *
+ * Only available for SND_SEQ_USER_CLIENT clients.
+ */
+int snd_seq_client_info_get_pid(const snd_seq_client_info_t *info)
+{
+	assert(info);
+	return info->pid;
+}
+
+/**
  * \brief (DEPRECATED) Get the event filter bitmap of a client_info container
  * \param info client_info container
  * \return NULL if no event filter, or pointer to event filter bitmap
diff --git a/src/seq/seq_hw.c b/src/seq/seq_hw.c
index d033367..578ef12 100644
--- a/src/seq/seq_hw.c
+++ b/src/seq/seq_hw.c
@@ -32,10 +32,11 @@ const char *_snd_module_seq_hw = "";
 #ifndef DOC_HIDDEN
 #define SNDRV_FILE_SEQ		ALSA_DEVICE_DIRECTORY "seq"
 #define SNDRV_FILE_ALOADSEQ	ALOAD_DEVICE_DIRECTORY "aloadSEQ"
-#define SNDRV_SEQ_VERSION_MAX	SNDRV_PROTOCOL_VERSION(1, 0, 1)
+#define SNDRV_SEQ_VERSION_MAX	SNDRV_PROTOCOL_VERSION(1, 0, 2)
 
 typedef struct {
 	int fd;
+	int version;
 } snd_seq_hw_t;
 #endif /* DOC_HIDDEN */
 
@@ -100,6 +101,10 @@ static int snd_seq_hw_get_client_info(snd_seq_t *seq, snd_seq_client_info_t * in
 		/*SYSERR("SNDRV_SEQ_IOCTL_GET_CLIENT_INFO failed");*/
 		return -errno;
 	}
+	if (hw->version < SNDRV_PROTOCOL_VERSION(1, 0, 2)) {
+		info->card = -1;
+		info->pid = -1;
+	}
 	return 0;
 }
 
@@ -368,6 +373,10 @@ static int snd_seq_hw_query_next_client(snd_seq_t *seq, snd_seq_client_info_t *i
 		/*SYSERR("SNDRV_SEQ_IOCTL_QUERY_NEXT_CLIENT failed");*/
 		return -errno;
 	}
+	if (hw->version < SNDRV_PROTOCOL_VERSION(1, 0, 2)) {
+		info->card = -1;
+		info->pid = -1;
+	}
 	return 0;
 }
 
@@ -480,6 +489,7 @@ int snd_seq_hw_open(snd_seq_t **handle, const char *name, int streams, int mode)
 		return -ENOMEM;
 	}
 	hw->fd = fd;
+	hw->version = ver;
 	if (streams & SND_SEQ_OPEN_OUTPUT) {
 		seq->obuf = (char *) malloc(seq->obufsize = SND_SEQ_OBUF_SIZE);
 		if (!seq->obuf) {
-- 
2.1.4