alsa-gobject: add library to operate ALSA Sequencer character device without queue feature

[GitHub pull_request - opened]

alsa-project/alsa-gobject pull request #10 was opened from takaswie:

This request is to add a new library, libalsaseq, to operate ALSA Sequencer
character device.

In design of ALSA Sequencer, one character device is added to Linux system.
Usually a special file, '/dev/snd/seq', is used for the character device.
Userspace applications can operate ALSA Sequencer via the character device.

The library supports functionalities of ALSA Sequencer but without
queue-related ones.

The library includes some GObject-derived object. ALSASeq.UserClient
maintains file descriptor of ALSA Sequencer character device, thus it's
the center of user operation. The other objects represent data structures
in UAPI of ALSA Sequencer.

 * ALSASeqSystemInfo - struct snd_seq_system_info
 * ALSASeqClientInfo - struct snd_seq_client_info
 * ALSASeqClientPool - struct snd_seq_client_pool
 * ALSASeqPortInfo - struct snd_seq_port_info
 * ALSASeqSubscribeData - struct snd_seq_port_subscribe

The library includes some GObject boxed object just to represent data
structures. ALSASeq.Addr is a thin wrapper to struct snd_seq_addr, and
ALSASeq.Tstamp is a thin wrapper to struct snd_seq_timestamp.

For operations without instances of ALSASeq.UserClient, the library
has some global APIs.

ALSA Sequencer has some macros. They're represented as GObject
enumerations and flags.

 * ALSASeq.ClientType - one of NO_CLIENT, USER_CLIENT, KERNEL_CLIENT
 * ALSASeq.FilterAttrFlag - SNDRV_SEQ_FILTER_XXX
 * ALSASeq.PortCapFlag - SNDRV_PORT_CAP_XXX
 * ALSASeq.PortAttrFlag - NDRV_SEQ_PORT_TYPE_XXX
 * ALSASeq.EventType - SNDRV_SEQ_EVENT_XXX
 * ALSASeq.EventTimestampMode - SNDRV_SEQ_TIME_STAMP_XXX
 * ALSASeq.EventTimeMode - SNDRV_SEQ_TIME_MODE_XXX
 * ALSASeq.EventLengthMode - SNDRV_SEQ_EVENT_LENGTH_XXX
 * ALSASeq.EventPriorityMode - SNDRV_SEQ_PRIORITY_XXX
 * ALSASeq.PortSubscribeFlag - SNDRV_SEQ_PORT_SUBS_XXX
 * ALSASeq.QuerySubscribeType - SNDRV_SEQ_QUERY_SUBS_XXX

Some specific values for addressing are also represented by GObject
enumerations and flags.

 * ALSASeq.SpecificAddress - SNDRV_SEQ_ADDRESS_XXX
 * ALSASeq.SpecificClientId - SNDRV_SEQ_CLIENT_XXX
 * ALSASeq.SpecificPortId - SNDRV_SEQ_PORT_SYSTEM_XXX
 * ALSASeq.SpecificQueueId - SNDRV_SEQ_QUEUE_XXX

ALSA Sequencer has many types of event. The library has an GObject
abstract object, ALSASeq.Event. Two objects are derived from it:

 * ALSASeq.EventFixed
 * ALSASeq.EventVariable

The former has some ways to access to the data of event. The data is
represented by GObject boxed object if it's complicated structure:

 * ALSASeq.EventDataConnect - struct snd_seq_connect
 * ALSASeq.EventDataNote - struct snd_seq_ev_note
 * ALSASeq.EventDataCtl - struct snd_seq_ev_ctrl
 * ALSASeq.EventDataResult - struct snd_seq_result
 * ALSASeq.EventDataQueue - struct snd_seq_ev_queue_control

The latter is for events to have variable length of data blob.

ALSASeq.UserClient has 'schedule_event' API to schedule arbitrary
event. It also has 'handle-event' GObject signal for applications
to handle asynchronous event as an instance of ALSASeq.EventFixed or
ALSASeq.EventVariable.

The library doesn't have support for below structures since they're useless
practically:

 * struct snd_seq_event_bounce
 * struct snd_seq_running_info

In my later work, queue functions will be added.

Request URL   : https://github.com/alsa-project/alsa-gobject/pull/10
Patch URL     : https://github.com/alsa-project/alsa-gobject/pull/10.patch
Repository URL: https://github.com/alsa-project/alsa-gobject