linux-kernel - Re: [PATCH] FB: add early fb blank feature.

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Date:	Thu, 15 Sep 2011 12:53:13 +0300
From:	Tomi Valkeinen <tomi.valkeinen@...com>
To:	Inki Dae <inki.dae@...sung.com>
Cc:	FlorianSchandinat@....de, linux-fbdev@...r.kernel.org,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	kyungmin.park@...sung.com
Subject: Re: [PATCH] FB: add early fb blank feature.

Hi,

On Fri, 2011-09-09 at 14:03 +0900, Inki Dae wrote:
> this patch adds early fb blank feature that this is a callback of
> lcd panel driver would be called prior to fb driver's one.
> in case of MIPI-DSI based video mode LCD Panel, for lcd power off,
> the power off commands should be transferred to lcd panel with display
> and mipi-dsi controller enabled because the commands is set to lcd panel
> at vsync porch period. on the other hand, in opposite case, the callback
> of fb driver should be called prior to lcd panel driver's one because of
> same issue. now we could handle call order to fb blank properly.
> 
> the order is as the following:
> 
> at fb_blank function of fbmem.c
>   -> fb_early_notifier_call_chain()
>      -> lcd panel driver's early_set_power()
>   -> info->fbops->fb_blank()
>      -> fb driver's fb_blank()
>   -> fb_notifier_call_chain()
>      -> lcd panel driver's set_power()

I'm not familiar with the lcd.c, so I may be talking nonsense, but I
don't quite understand the need for this patch. If you have some kind of
panel driver, shouldn't the panel driver handle power off in just one
place?

With omapfb and omapdss, the omapfb's fb_blank function just calls power
off in the panel driver, which handles all necessary actions. Is your
model somehow totally different?

 Tomi


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