Date: Thu, 25 Dec 2008 10:53:33 +0100 From: Andre Albsmeier <Andre.Albsmeier@siemens.com> To: freebsd-hackers@freebsd.org Cc: Andre.Albsmeier@siemens.com Subject: Writing device drivers: How to access a specific memory area? Message-ID: <20081225095333.GA12699@curry.mchp.siemens.de>
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Hello all, I am writing a driver which needs to access memory at a specific location. The location depends on what the BIOS has configured into the host bridge. For example, my current machine uses an Intel 975X chipset and the memory location I am interested in has been set to 0xFED14000 and is 16KB in size (this is MCHBAR of the 975X memory hub). I have no idea how to access this space from my driver. I have played around with bus_alloc_resource() but this only gives me back NULL. However, a devinfo -r gives me: nexus0 npx0 acpi0 Interrupt request lines: 9 I/O ports: 0x10-0x1f ... 0x800-0x87f I/O memory addresses: 0x0-0x9ffff 0xc0000-0xdffff 0xe0000-0xfffff 0x100000-0x7fffffff 0xf0000000-0xf3ffffff 0xfec00000-0xfec00fff 0xfed13000-0xfed19fff <--- 0xfed1c000-0xfed1ffff 0xfed20000-0xfed3ffff 0xfed50000-0xfed8ffff 0xfee00000-0xfee00fff 0xffb00000-0xffbfffff 0xfff00000-0xffffffff cpu0 ... The line marked with <--- shows the range which includes the location I am interested in. It is probably assigned to the acpi0 device. How do I proceed from this? Do I have to hack around in the ACPI-Code? I don't hope so ;-) I only need access to this memory location during the probe of my driver to read some configuration data. I do not need to access it later anymore... Thanks a lot for any hints, -Andre
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