Re: [PATCH] Fix FB console blanking

[Dmitry Baryshkov <dbaryshkov@gmail.com>]

Geert Uytterhoeven wrote:
> On Mon, 24 Nov 2008, Dmitry Baryshkov wrote:
>> The commit aef7db4bd5a3b6068dfa05919a3d685199eed116 fixed the problem
>> with recursive locking in fb blanking code if blank is caused by user
>> setting the /sys/class/graphics/fb*/blank. However this broke the fbcon
>> timeout blanking.
> 
> Can you please explain a bit more about what `broken' means? What happens, how
> can I reproduce it?

If you use a driver that defines ->fb_blank operation and at the same 
time that driver relies on other driver (e.g. backlight or lcd class) to 
blank the screen, when the fbcon times out and tries to blank the fb, it 
will call only fb driver blanker and won't notify the other driver. Thus 
FB output is disabled, but the screen isn't blanked.

> 
> Thanks!
> 
>> Restore fbcon blanking and at the same time apply the proper fix for the
>> above problem: if fbcon_blank is called with FBINFO_FLAG_USEREVENT, we
>> are already called through notification from fb_blank, thus we don't
>> have to blank the fb again.
> 
> Is it just an issue of blanking again if the display is already blanked?

Yes. (at least the original problem that I stumbled upon).

> 
>> Signed-off-by: Dmitry Baryshkov <dbaryshkov@gmail.com>
>> ---
>>  drivers/video/console/fbcon.c |    9 +++------
>>  1 files changed, 3 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c
>> index 9cbff84..2f2f0f9 100644
>> --- a/drivers/video/console/fbcon.c
>> +++ b/drivers/video/console/fbcon.c
>> @@ -2400,16 +2400,13 @@ static int fbcon_blank(struct vc_data *vc, int blank, int mode_switch)
>>  
>>   	if (!fbcon_is_inactive(vc, info)) {
>>  		if (ops->blank_state != blank) {
>> -			int ret = 1;
>> -
>>  			ops->blank_state = blank;
>>  			fbcon_cursor(vc, blank ? CM_ERASE : CM_DRAW);
>>  			ops->cursor_flash = (!blank);
>>  
>> -			if (info->fbops->fb_blank)
>> -				ret = info->fbops->fb_blank(blank, info);
>> -			if (ret)
>> -				fbcon_generic_blank(vc, info, blank);
>> +			if (!(info->flags & FBINFO_MISC_USEREVENT))
>> +				if (fb_blank(info, blank))
>> +					fbcon_generic_blank(vc, info, blank);
>>  		}
>>  
>>  		if (!blank)
> 
> Gr{oetje,eeting}s,
> 
> 						Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
> 							    -- Linus Torvalds


-- 
With best wishes
Dmitry


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