Re: Console unregistration questions

["Antonino A. Daplas" <adaplas@gmail.com>]

On Fri, 2007-04-27 at 08:14 -0700, Jesse Barnes wrote:
> 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).

I'll try modifying fbcon + your patch this weekend so we can selectively
unbind framebuffers.

Tony



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