On Mon, 22 May 2023 10:00:40 +0200, Takashi Iwai wrote:
On Mon, 22 May 2023 09:34:45 +0200, Jaroslav Kysela wrote:
On 19. 05. 23 11:31, Takashi Iwai wrote:
Starting from this commit, we add the basic support of UMP (Universal MIDI Packet) events on ALSA sequencer infrastructure. The biggest change here is that, for transferring UMP packets that are up to 128 bits, we extend the data payload of ALSA sequencer event record when the client is declared to support for the new UMP events.
A new event flag bit, SNDRV_SEQ_EVENT_UMP, is defined and it shall be set for the UMP packet events that have the larger payload of 128 bits, defined as struct snd_seq_ump_event.
For applications that want to access the UMP packets, first of all, a sequencer client has to declare the user-protocol to match with the latest one via the new SNDRV_SEQ_IOCTL_USER_PVERSION; otherwise it's treated as if a legacy client without UMP support.
Then the client can switch to the new UMP mode (MIDI 1.0 or MIDI 2.0) with a new field, midi_version, in snd_seq_client_info. When switched to UMP mode (midi_version = 1 or 2), the client can write the UMP events with SNDRV_SEQ_EVENT_UMP flag. For reads, the alignment size is changed from snd_seq_event (28 bytes) to snd_seq_ump_event (32 bytes). When a UMP sequencer event is delivered to a legacy sequencer client, it's ignored or handled as an error.
The internal struct snd_seq_event_cell is also extended by 4 bytes. I think that it is worth to note this in this commit (the memory footprint is slightly growing).
Yes, will do that. But note that the size growth of snd_seq_event_cell happens only for 32bit archs (there was already padding on 64bit archs).
Maybe handle !SND_UMP here, but we can wait, if someone really requires this optimization.
Right, I began with that, but I threw it away in the end as it becomes unnecessarily complex.
Actually the optimization with CONFIG_SND_SEQ_UMP was already done; unless CONFIG_SND_SEQ_UMP is set, the old size of snd_seq_event_cell is still kept. The definition of union __snd_seq_event in seq_memory.c takes care of the conditional builds.
What I meant was to adjust the cell size dynamically depending on the supported midi_version, and this will make things too flaky.
Takashi