speakup bug
From: John G. Heim
Date: Sat Mar 03 2012 - 12:18:14 EST
I need help fixing a bug in the driver for serial hardware speech synths in
the speakup screen reader. According to the comments in the code, it is in a
part of the code that is trying to "steal" the serial port.
First it calls request_region and when that fails (it always fails), it
calls __release_region(&then it calls release_region again to see if
__release_region worked. But it never works because the region being
requested is already taken.
The code in question is in 2 source code files in drivers/staging/speakup.
It starts in serialio.c on line 38. Here it calls a function named
synth_request_region which in turn, calls request_region. On line 41 it
calls __release_region, and on line 42 it calls synth_request_region again.
The function synth_request_region (which calls request_region) is in a file
named synth.c. But this code always fails. Here is a kind of simplified
version of it...
int error;
struct resource tmp;
tmp .name = "ltlk";
tmps.start = 0x3F8;
tmp.end = 0x3FF;
tmp.flags = IORESOURCE_BUSY;
error = request_resource (&ioport_resource, &tmp);
The error returned is always -16. I looked at the code in kernel/resource.c
where the request_region function is defined. It builds a linked list of
resources with start & end addresses. If you request a region that is
already within the start-end range of a resource already in the list, it
returns an error code. But it looks as if the region for a serial port,
0x3f8 - 0x3ff, in ioport_resource cannot be reserved because the entire
range from 0x000 through 0xcf7 is already taken by something named "PCI Bus
0000:00". Therefore calling request_resource always fails and the driver
for the speech synth errors out.
And therefore I can't use my hardware speech synth without modifying the
kernel code. If you comment out the line that checks the return code from
request_region, it works. So you have to modify the kernel code and compile
a custom kernel to use a hardware speech synth. That's not such a problem
for me but it is for a lot of people. Plus, the grml live CD doesn't work
with hardware speech. That is a problem for me.
Can anyone tell me how to fix this so it can be patched in the official
kernel code?
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