Re: [BUG] pnpbios breaks floppy support

From: Robert Hancock
Date: Sun Feb 01 2009 - 15:12:05 EST


Philippe De Muyter wrote:
On Sun, Feb 01, 2009 at 01:08:33AM -0600, Robert Hancock wrote:
Philippe De Muyter wrote:
Hello linux experts,
Today I tried to upgrade a PC's kernel from 2.6.11 to 2.6.22, and
I saw some strange messages when booting :
Floppy drive(s): fd0 is 1.44M
floppy0: Floppy io-port 0x03f2 in use
Previously, I had :
Floppy drive(s): fd0 is 1.44M
FDC 0 is a post-1991 82077
Needless to say, my floppy hardware works perfectly, and my floppy
was usable with the old kernel, while the floppy is now inaccessible
with the new kernel. Even /dev/fd0 does not exist anymore.
Searching for a cause to that problem, I saw the following messages
before the floppy probe in the new kernel :
PnPBIOS: Scanning system for PnP BIOS support...
PnPBIOS: Found PnP BIOS installation structure at 0xc00fd5e0
PnPBIOS: PnP BIOS version 1.0, entry 0xf0000:0x5ba3, dseg 0xf0000
PnPBIOS: 17 nodes reported by PnP BIOS; 17 recorded by driver
[...]
pnp: 00:07: ioport range 0x3f0-0x3f1 has been reserved
pnp: 00:07: ioport range 0x3f3-0x3f3 has been reserved
[...]
Searching the web and the outdated pnp kernel documentation, I
finally found an option to add to my kernel parameters line :
pnpbios=off
Now my floppy works again, but I am not really satisfied.
What do I loose with the 'pnpbios=off' option ?
Isn't there a smoother option to allow pnpbios but avoiding to reserve
floppy's io-ports ?
Should I modify rather /drivers/block/floppy.c or /drivers/pnp/*.c
to make pnpbios and floppy driver coexist peacefully ? And is there
an example of such modifications for other standard peripherals ?
Presumably the problem is that your BIOS marks the IO ports used by the floppy controller as reserved which prevents the floppy driver from binding to them. (2.6.11 probably was before we even processed PnP reserved regions.)

I think we now have handling for the case where the reservations overlap PCI devices, but I think it's the first I've heard of them overlapping the floppy IO ports..

I should have added that, when started with pnpbios enabled, I have found the following in /sys/devices/pnp0/ :

$ cat 00:03/id
PNP0700
$ cat 00:03/resources state = active
io 0x3f4-0x3f5
io 0x3f2-0x3f2
irq 6
dma 2
$ cat 00:03/options
port 0x3f4-0x3f4, align 0x0, size 0x2, 16-bit address decoding
port 0x3f2-0x3f2, align 0x0, size 0x1, 16-bit address decoding
irq 6 High-Edge
dma 2 8-bit compatible

AFAIK, PNP0700 is the pnp id for the standard floppy disk,
and the resources and options files describe the expected io-ports
of the floppy disk, so this does not seem to be an error in the bios.

There's likely another resource with id of PNP0C01 or PNP0C02 (Motherboard resources) which contains that same IO port range.
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