Re: PM/FB/gxfb: add config option that allows disabling of VT switch during suspend

On 10/03/08 18:14 -0400, Andres Salomon wrote:

On Mon, 10 Mar 2008 14:51:18 -0700
Andrew Morton [off-list ref] wrote:

quoted

On Mon, 10 Mar 2008 17:44:24 -0400
Andres Salomon [off-list ref] wrote:

quoted

On Mon, 10 Mar 2008 14:19:39 -0700
Andrew Morton [off-list ref] wrote:

quoted

It would be far preferable to do this via a kernel boot parameter rather
than via a kernel rebuild.

Well, it shouldn't be supported at _all_ unless the framebuffer driver
supports it; you're asking for it to be converted to something like the
following?



#ifdef CONFIG_FBDEV_SUPPORTS_NOSWITCH
static int no_vt_switch;
#endif

int pm_prepare_console(void)
{
#ifdef CONFIG_FBDEV_SUPPORTS_NOSWITCH
	if (no_vt_switch)
		return 0;
#endif
	...
}

#ifdef CONFIG_FBDEV_SUPPORTS_NOSWITCH
module_param(no_vt_switch, int, 0);
MODULE_PARM_DESC(no_vt_switch, "...");
#endif


If so, that means extra #ifdef's sprinkled throughout the code.  Note
that most framebuffer drivers won't be supporting this, and those that
do will almost certainly always want vt switching turned off..

I don't think you need any ifdefs or config options at all, do you?  Just
add a new module parameter to this driver and some little interface into
the PM core which allows the driver to set no_vt_switch?

That's a possibility, but doesn't adding hooks into PM core for two
drivers (lxfb and gxfb) seems like overkill?  I also don't really see
anyone needing to switch back and forth between VT_SWITCH and
NO_VT_SWITCH other than to work around possible bugs in the register
save/restore code..

I like Andrew's idea.  I wager This won't be Geode specific for long.
Either other drivers will get the hint and add real save/restore code
or the GPU subystem code being worked on by the X folks will come along
and make the VT switch obsolete for everybody.  Either way, I see hooks
in the PM core as generic love that everybody can benefit from.

Jordan

-- 
Jordan Crouse
Systems Software Development Engineer 
Advanced Micro Devices, Inc.


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