Re: Add a "enable" sysfs attribute to the pci devices to allow userspace (Xorg) to enable devices without doing foul direct access

[Greg KH <greg@kroah.com>]

On Fri, May 05, 2006 at 04:43:15PM -0400, Jon Smirl wrote:
> >On 5/5/06, Greg KH <greg@kroah.com> wrote:
> >> Who cares who "enabled" the device.  Remember, the majority of PCI
> >> devices in the system are not video ones.  Lots of other types of
> >> devices want this ability to enable PCI devices from userspace.  I've
> >> been talking with some people about how to properly write PCI drivers in
> >> userspace, and this attribute is a needed part of it.
> 
> The problem is not who 'enabled' the device. The problem is who owns
> the state that has been loaded into the device. Without a mechanism
> like open there is no way to serialize the programs trying to set
> state into the device.
> 
> fbdev and X have this fight currently. On every VT swap they each
> reload their state into the video hardware. There is no coordination
> so both systems have to assume worst case and rebuild everything. This
> is not a good environment to program in. Every time one of the systems
> starts using some new feature of hardware (like acceleration
> functions) new state recovery code needs to be written.

Yes, I agree that this is a big issue and one that needs to be worked
on.  However, this simple "enable" file has nothing to do with that
issue at all...

thanks,

greg k-h
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