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

[Kyle Moffett]

On May 7, 2006, at 09:12:01, Pavel Machek wrote:
> > > It has everything to do with the 'enable' file. The 'enable' file  
> > > lets you change the state of the hardware without an ownership  
> > > mechanism. Other device users will not be notified of the state  
> > > change. Since the other users can't be sure of the state of the  
> > > hardware when they are activated, they will have to reload their  
> > > state into the hardware on every activation.
> >
> > you seem to miss the fact that this can be done now without the  
> > enable flag, setpci can be used to disable the BARs, again the  
> > enable flag doesn't change that....
>
> ...well, when you launch setpci, you are firmly in 'unsupported'  
> land.  While 'enable' sounds like something where users expect it  
> to be supported.

*Especially* since there are a number of users (including myself) who  
have tendencies to go wandering around sysfs tinkering with the  
available values.  Not having seen this thread, I would have had no  
problem doing "echo -n 0 >enable" on some device thinking that it was  
a fairly standard way to turn off the power to my soundcard when I'm  
not using it, and likely result in a kernel panic because I suddenly  
disabled the BARs on the device out from under the driver.

Cheers,
Kyle Moffett

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/