Re: [Dri-devel] Re: DRM and pci_driver conversion

[ebiederm@xmission.com (Eric W. Biederman)]

Linus Torvalds <torvalds@osdl.org> writes:

> On Sat, 25 Oct 2003, Egbert Eich wrote:
> > 
> > Speaking of XFree86: when I developed the PCI resource stuff in 
> > XFree86 I was trying to get support from kernel folks to get the 
> > appropriate user space interfaces into the kernel. When I got 
> > nowhere I decided to do everything myself. 
> 
> There won't be any "user space interfaces". There are perfectly good 
> in-kernel interfaces, and anybody who needs them needs to be in kernel 
> space. Ie the kernel interfaces are for kernel modules, not for user space 
> accesses.

Well almost.    There is still one significant flaw in the kernel space stuff.

The BIOS can specify arbitrary regions as reserved in the E820 map and then
a kernel driver can't use that region itself.  This shows up in corner
cases where the resource on the PCI device is a boolean rather than
a general purpose thing.  Particularly for mtd map drivers to allow
flashing your ROM from linux this is a problem.

This is not required for 2.6.0 but it would be nice to actually be able
to reliably reserve resources in kernel drivers.

Eric


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