Re: Console unregistration questions

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Thursday, April 26, 2007, Antonino A. Daplas wrote:
> I have no problems with the purpose of this patch, but I would like what
> other kernel developers, both fbdev and non-fbdev, think about this.
>
> The main problem with this version is it's possible to have more than 1
> fb driver mapped to each console (and people do that).  So if one of
> them unregisters, it will also unbind the other one. Code-wise, it's not
> a problem.  But users will not expect that behavior.
>
> It's fixable though, as unbind_con_driver() also accepts the first and
> last parameter.  fbcon_fb_unbind() will have to walk con2fbmap[], so
> something like this untested code instead:
>
> static int fbcon_fb_unbind(int idx) {
> 	for (i = 0; i < MAX_NR_CONSOLES; i++) {
> 		/* Assure we do not unbind other drivers */
> 		if (idx == con2fbmap[i])
> 			/* can be optimize to minimize multiple calls to
> 			 	unbind_con_driver() */
> 			unbind_con_driver(&fb_con, i, i, 0);
> 	}
> ]
>
> Besides the above, we still have to make adjustments to fbcon so it can
> handle one driver going away and while still managing other loaded
> drivers.

Unbinding from specific consoles would indeed be much better, and provide 
more intuitive behavior.  I just wasn't sure how to do it offhand in 
fbcon; I'll try your snippet, looks like it should work nicely (at and 
worst we'll have 64 calls to unbind_con_driver, so I don't think batching 
is an issue).

Thanks,
Jesse

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