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 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