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

[Kyle Moffett <mrmacman_g4@mac.com>]

On May 6, 2006, at 19:16:25, Krzysztof Halasa wrote:
> "Jon Smirl" <jonsmirl@gmail.com> writes:
> > > The card in question _has_ a driver. I, for example, just need a  
> > > way to write EEPROM data to it (vendor/device ID etc). The card  
> > > has to be selected by PCI bus and slot (device) number, not by  
> > > device class and/or IDs, because it can contain garbage and/or  
> > > some generic IDs with generic device class.
> >
> > Hardware like you describe violates the PCI spec
>
> What exactly does it violate?

"device class and/or IDs ... can contain garbage".  That seems to  
violate PCI spec to me.

> > I would probably handle this by writing an unbound device driver  
> > that exposes a sysfs file for bus:slot. When you write the  
> > bus:slot to the file it would then bind to the appropriate  
> > hardware and enable it. The newly bound driver would support the  
> > driver firmware loader interface as a means of getting your data in.
>
> What is also needed is that end users perform this task from time  
> to time. They generally don't want to have to compile the kernel :-)
>
> You know, even now it can be done (entirely in userspace), and only  
> enabling the device seems a bit dangerous.

Jon Smirl gave a great description of exactly how to write such a  
"driver".  I seem to recall that we already have the ability to  
trigger manual PCI binding by bus:slot number; in combination with an  
appropriate "write EEPROM with firmware file" driver that has no  
default list of PCI devices; you could easily manually trigger a bind  
of the device.  On the other hand I would personally never put such a  
device in my system, what if the garbage device IDs happened to match  
a device with poorly-written PCI IDE drivers that panic when they  
bind to a device which does not match their expectations?  In any  
case what you really need for all those cases is a simplistic stub  
driver that provides some sort of in-kernel mutual exclusion.

Cheers,
Kyle Moffett

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