[Coco] questions about sharing memory amongst device drivers in os-9
aawolfe at gmail.com
Sun Nov 15 13:55:31 EST 2009
I've updated the server code and drivewire nitros-9 drivers to allow
up to seven "virtual" serial ports over the bitbanger. Each virtual
port is terminated on the host in its own PTY.
In order to do this, I created additional device descriptors with
different V.PORT values but pointing to the same scwdt driver. I use
the port in calls to the driver to distinguish between them.
Everything works fine for writes, since these do not require any
coordination between devices. I can simultaneously list out multiple
files on the coco to separate windows/session on my PC, no problem.
Drivewire really is fast!
However, for incoming data I have an issue that I could use some
guidance with. Each device creates its own memory area. The first
device to use the scwdt driver shares it's area with the driver, so
they can see the same memory, where the input buffers, status flags
etc are. I can run a shell on the first port I iniz, whichever port
that might be, and everything's great.
The second third etc ports are getting their own separate device
memory area, I guess this makes sense in a real world device where
they would have separate interrupt handlers. But in this project, I
need to use a single interrupt handler to feed multiple "devices".
Here's an example of what I mean, T1 and T2 have different static mem
areas, but both use scdwt. Since T1 has the same addr (6000) as the
IRQ handler, it can do writes. T2 can only do reads:
Device Table at: 6D00
Device Desc Driver Static File Usr
Name Port Name Mem Manager Cnt
----------- ------------- ------- ---
DD 070000 rbdw3 6B00 RBF 05
Term 07FFA0 VTIO 6A00 SCF 04
T1 07FF01 scdwt 6000 SCF 03
T2 07EE02 scdwt 5E00 SCF 01
Polling Table at: 6EFB
Device Table at: 6D00
Device Driver IRQ Flip
Port Mem Name Vector &Mask Pty
---- ---- ------------ ----- ---
60B4 6000 scdwt E5C6 00 01 0A
All I really need is some shared memory or other means to get bytes
into each device's buffer from the central interrupt handler, or let
the devices come get the data from a central set of buffers,
whichever.. and then the ISR needs to know the process IDs (V.BUSYs
basically) of each device so it can send the wake signal. Actually I
have the signal handler written already but no way to get the PIDs
into it's table.
Is there a standard os-9 way to do such a thing? Am I missing
something that would make this simpler? I've studied the os9 terch ref
and everything else I can find but nothing has become obvious to me
yet. Any advice is much appreciated.
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