[alsa-devel] [PATCH v2 2/3] Provide sequencer sound card number / PID via alsa-lib

[Takashi Iwai]

On Wed, 02 Mar 2016 19:26:26 +0100,
Martin Koegler wrote:
> 
> 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..24350b6 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 micro_version;

Better to keep the protocol version as is.

In the rest, you can compare like

	if (hw->version < SNDRV_PROTOCOL_VERSION(1, 0, 2))

and....

>  } 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->micro_version < SNDRV_PROTOCOL_MICRO(SNDRV_SEQ_VERSION_MAX)) {

... referring to SNDRV_SEQ_VERSION_MAX here is wrong.  The max number
will increase in the future, then this check shall fail, too.


thanks,

Takashi