Re: [linux-audio-dev] MIDI routing, FIFO's etc.

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Subject: Re: [linux-audio-dev] MIDI routing, FIFO's etc.
From: Jaroslav Kysela (perex_AT_suse.cz)
Date: su loka   10 1999 - 11:33:52 EDT


On Sun, 10 Oct 1999, David Olofson wrote:

> > I think that the big problem will be with the memory allocation, because
> > the allocation must be done inside kernel (use mmap from the user space?).
> > It's problem #1 and we should solve it firstly.
>
> There is a module called mbuff that's used with RTLinux for this
> purpose. It's based on the "heavy wizardry" in bttv.c, and I think
> the module should work w/o RTL... (Memory allocation from the
> standard kernel heap can never be hard real time anyway.)

I'm not sure, if using physical memory for events (my proposal and
probably mbuff does this, too) is a good idea. The question is, how long
will be an event. I'd like to see an event for complete wavetable
instrument (tens of megabytes). If we will use only physical memory
allocation and an user have only little memory, it will not work, but it
works perfectly with current implementations which use the virtual memory
(swap).

Onother thing: the process security. Do you thing that one shared memory
heap is a good solution for multi user / multi tasking system? I don't.
The memory heaps could be shared only among participants, but it's a
question, how to do it (duplicate information? - another memory wasting).

I also think that we should cooperate from beginning with Linus and Alan
Cox to make sure, that this code will be included into the standard kernel
tree.

A little dream:

Event - picture 768x576 from grabbed from the BTTV driver 8-bits per color
Event - Piano instrument 96kHz, 24-bit resolution

                                                Jaroslav

-----
Jaroslav Kysela <perex_AT_suse.cz>
SuSE Linux http://www.suse.com
ALSA project http://www.alsa-project.org


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