Date: Thu, 25 Dec 2008 13:57:00 +0000 From: Rui Paulo <rpaulo@freebsd.org> To: Andre Albsmeier <Andre.Albsmeier@siemens.com> Cc: freebsd-hackers@freebsd.org Subject: Re: Writing device drivers: How to access a specific memory area? Message-ID: <490EB16A-F626-4A40-9716-A02A32F04ED4@freebsd.org> In-Reply-To: <20081225095333.GA12699@curry.mchp.siemens.de> References: <20081225095333.GA12699@curry.mchp.siemens.de>
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On 25 Dec 2008, at 09:53, Andre Albsmeier wrote:
> 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).
You probably just need to do something like:
rid = PCI_BAR(number);
res = bus_alloc_resource_any(dev, SYS_RES_MEMORY, &rid, RF_ACTIVE);
And then,
bus_read_4(res, offset from specified PCI BAR);
>
>
> 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 ;-)
You'll probably need to create a fake ACPI child driver to access it.
Create your identify routine with something like:
static void mydriver_identify(driver_t *driver, device_t parent)
{
if (device_find_child(parent, "mydriver", -1) == NULL &&
mydriver_match(parent))
device_add_child(parent, "mydriver", -1);
}
mydriver_match() should check if you were given the acpi0 device.
>
>
> I only need access to this memory location during the
> probe of my driver to read some configuration data.
Is this pci configuration space ? If so, pci_read_config (man 9 pci)
should be just what you need.
Regards,
--
Rui Paulo
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