On Thu, 03 Jan 2002 14:24:19 -0500 Paul Davis <[EMAIL PROTECTED]> wrote:
> nice idea from a user-space perspective erik, but this doesn't take > into account the whole picture here. if the information is being > distributed to actual physical MIDI ports, then there needs to be > something that takes the message from the queue and delivers it to the > port's low level device driver. the code that does this would have to > be in the kernel, My idea was that the Midi Mapper was actually a userspace daemon. User space process connect to the daemon with a library. > where the semantics of sysv message queues don't > exist (since the API is for user space). > > besides, under POSIX, read(2) and write(2) are also atomic, Yes, but open() will not allow more than one program to open a device. That along with the multiplexing issues is why I was looking at message queues. > and finally, its not the right answer anyway because of MIDI running > status. note on/off messages are not always 3 bytes because of this > feature. I hadn't actually thought of this but it shouldn't be a problem. The running status messages are all on the physical layer and the daemon could simply translate back an forth between wire format and format used by the user space library. > moreover, there are several single byte MIDI "real time" > messages that can arrive at any time, even in the middle of a non-real > time MIDI message. Sorry, I'm not aware of these. Any more info? I do know of running status bytes but they seem to be filtered by the device driver. > this means that defining "a complete midi message" > is much more complex than you are suggesting. > > the MIDI specification includes a classic flow chart for a MIDI > parser, and if you become familiar with it (alas, its not online), Bummer! > it can be seen that there are no short circuits around the "wire" level > of the MIDI protocol. I'm still not totally convinced. By imposing certain small restrictions on what is allowed, this should still be possible. Erk -- +-----------------------------------------------------------+ Erik de Castro Lopo [EMAIL PROTECTED] (Yes it's valid) +-----------------------------------------------------------+ Laws of Thermodynamics: 1) You cannot win. 2) You cannot break even. 3) You cannot get out of the game.
