Messages in this thread | | | Date | Tue, 11 Apr 2006 16:59:38 -0700 | From | Ian Romanick <> | Subject | Re: Special handling of sysfs device resource files? |
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Ian Romanick wrote: > I'm in the process of modifying X to be civilized in it's handling of > PCI devices on Linux. As part of that, I've modified it to map the > /sys/bus/pci/device/*/resource[0-6] files instead of mucking about with > /dev/mem. > > This seems to mostly work, but I am having one problem. I map the > region by opening the file with O_RDWR, then mmap with > (PROT_READ|PROT_WRITE) and MAP_SHARED. In all cases, the open and mmap > succeed. However, for I/O BARs, the resulting pointer from mmap is > invalid. Any access to it results in a segfault and GDB says it's "out > of range".
I was a little mistaken about this. The BAR that causes the problem is not I/O. It *is* memory.
01:00.0 VGA compatible controller: Matrox Graphics, Inc. G400/G450 (rev 03) (prog-if 00 [VGA]) Subsystem: Matrox Graphics, Inc. Millennium G400 16Mb SGRAM Flags: bus master, medium devsel, latency 64, IRQ 11 Memory at cc000000 (32-bit, prefetchable) [size=32M] Memory at cfefc000 (32-bit, non-prefetchable) [size=16K] Memory at cf000000 (32-bit, non-prefetchable) [size=8M] Expansion ROM at cfee0000 [disabled] [size=64K]
When I open and mmap resource0 (the framebuffer) I get 0x2b9aa48ea000. When I open and mmap resource1 (the card's registers) I get 0x2b9aa68ea000. I can access the resource0 pointer all day long without problems. The firs access to the resource1 pointer results in a segfault.
> The base address of the BAR is page aligned, so its not a problem with > the alignment of mmap vs. the alignment of the BAR. What else could it > be? I'm pretty stumped. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2.1 (GNU/Linux)
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