[alsa-devel] Adding new (old) SNDRV_SEQ_PORT_TYPE_MIDI_* defines

[Adam Goode]

On Fri, Mar 13, 2015 at 4:07 AM, Clemens Ladisch <clemens at ladisch.de> wrote:

> Adam Goode wrote:
> > I found the /* TODO: read port flags from descriptors */ in
> > sound/usb/midi.c and was thinking about what to do to implement this.
> >
> > The first thing to do would be to ensure that all the flags from the
> > element descriptors in the USB MIDI standard are available for returning
> > from snd_seq_port_info_get_type.
>
> I don't know of any class-compliant USB MIDI device that actually has
> elements and declares them in its descriptors.
>
> Do you have anything that would allow us to test this?
>
> > I propose adding these flags to ALSA:
> >
> > #define SNDRV_SEQ_PORT_TYPE_MIDI_CLOCK  (1<<7)  /* MIDI CLOCK compatible
> device */
> > #define SNDRV_SEQ_PORT_TYPE_MIDI_TIME_CODE (1<<8) /* MTC compatible
> device */
> > #define SNDRV_SEQ_PORT_TYPE_MIDI_MACHINE_CONTROL (1<<9) /* MMC
> compatible device */
> > #define SNDRV_SEQ_PORT_TYPE_MIDI_EFX    (1<<21) /* Audio effects
> processor device */
> > #define SNDRV_SEQ_PORT_TYPE_MIDI_PATCH_BAY (1<<22) /* MIDI patcher or
> router device */
> > #define SNDRV_SEQ_PORT_TYPE_MIDI_DLS1   (1<<23) /* DownLoadable Sounds
> Standard Level 1 compatible device */
> > #define SNDRV_SEQ_PORT_TYPE_MIDI_DLS2   (1<<24) /* DownLoadable Sounds
> Standard Level 2 compatible device */
> >
> > Thoughts? I can send a couple patches for the kernel and alsa-lib. I
> don't
> > think this is a breaking change.
>
> The first three flags might be useful.  Their problem is that software
> cannot rely on them being set for all ports connected to devices that
> support these features, but the other PORT_TYPE_MIDI flags have the same
> problem.
>
> I don't see any useful application for the other four flags.  I think
> the driver should just ignore them.
>

Hmm, it would be nice to be able to expose all the descriptors the hardware
is providing. But I do worry about polluting this bitmap with all these
flags. I'll have to think about this a little more.


Thanks,

Adam