Messages in this thread | | | From | Roland Dreier <> | Date | Wed, 06 Oct 2004 15:43:13 -0700 | Subject | Re: Driver access ito PCI card memory space question. |
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Alan> Then I do request_mem_area(0xfeaff000,4095, "SSE");
Alan> Then I do a readl(0xfeaff100); and get this:
Alan> Unable to handle kernel paging request at virtual address feaff100
You can't blindly access an address from your device's BARs; on many architectures PCI access needs setting up and/or addresses need munging before use. The API you need is ioremap().
You need to do something like:
void __iomem *mybase = ioremap(pci_resource_start(my_pdev, 0), 4095); u32 value = readl(mybase + 0x100);
(Delete the __iomem annotation for kernels before 2.6.9).
The "Linux Device Drivers" online book, available at <http://www.xml.com/ldd/chapter/book/> will probably be pretty helpful. In fact if you're serious about writing drivers, you should buy a dead-tree copy.
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