[alsa-devel] Serial MIDI driver for PL011 - as found on BCM2835 hardware

[Takashi Iwai]

At Wed, 22 Oct 2014 09:24:35 +1100,
Kim Taylor wrote:
> 
> On Tue, 2014-10-21 at 09:20 +0200, Daniel Mack wrote:
> > Hi,
> > 
> > Thanks for sharing this!
> > 
> > On 10/21/2014 01:40 AM, Kim Taylor wrote:
> > > I've written a driver for raw MIDI using the PL011. It is obviously
> > > based on the snd-serial-u16550 module, with a couple of improvements:
> > >
> > >  - I've implemented a drain() callback.
> > > 
> > >  - I've also implemented a half duplex mode based on a timer callback
> > > which was necessary for reliable communication with my eMagic Unitor 8
> > > hardware. (Testing with a serial link to other hardware shows that the
> > > full duplex mode is also working.)
> > 
> > So I guess you could patch the existing driver to make it work for your
> > use case, right? I haven't looked at the code in detail, but from what
> > you describe, that should be possible.
> 
> I'm not sure about that. As it uses a different UART chip, there is a
> new probe() function, it uses memory mapped I/O, instead of i386
> inb/outb, it gathers information from the ARM AMBA bus...
> 
> The only things that would remain unchanged are the output_trigger() and
> output_write() functions. One possibility might be to abstract out all
> read/write operations using function pointers, however, I believe that
> the new driver is different enough to constitute a new module.
> 
> Or maybe there should be a third module (for example snd-serial-core,
> containing any common functions, exporting them to both
> snd-serial-u16550 and snd-serial-pl011?

Yes, that sounds good.  Of course, it depends on the volume they can
share.  If there are so few, no big merit to split to modules.  Let's
see.


Takashi