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
