Re: [PATCH V2 2/9] drm/panel: add pre_enable and post_disable routines

From: Thierry Reding <thierry.reding@gmail.com>
To: Ajay Kumar <ajaykumar.rs@samsung.com>
Cc: linux-samsung-soc@vger.kernel.org, seanpaul@google.com,
	joshi@samsung.com, dri-devel@lists.freedesktop.org,
	ajaynumb@gmail.com, prashanth.g@samsung.com
Subject: Re: [PATCH V2 2/9] drm/panel: add pre_enable and post_disable routines
Date: Tue, 22 Apr 2014 10:19:49 +0200	[thread overview]
Message-ID: <20140422081948.GA17275@ulmo> (raw)
In-Reply-To: <1398119958-32005-3-git-send-email-ajaykumar.rs@samsung.com>

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On Tue, Apr 22, 2014 at 04:09:11AM +0530, Ajay Kumar wrote:
> Most of the panels need an init sequence as mentioned below:
> 	-- poweron LCD unit/LCD_EN
> 	-- start video data
> 	-- poweron LED unit/BL_EN
> And, a de-init sequence as mentioned below:
> 	-- poweroff LED unit/BL_EN
> 	-- stop video data
> 	-- poweroff LCD unit/LCD_EN
> With existing callbacks for drm panel, we cannot accomodate such panels,
> since only two callbacks, i.e "panel_enable" and panel_disable are supported.
> 
> This patch adds:
> 	-- "pre_enable" callback which can be called before
> 	the actual video data is on, and then call the "enable"
> 	callback after the video data is available.
> 
> 	-- "post_disable" callback which can be called after
> 	the video data is off, and use "disable" callback
> 	to do something before switching off the video data.
> 
> Now, we can easily map the above scenario as shown below:
> 	poweron LCD unit/LCD_EN = "pre_enable" callback
> 	poweron LED unit/BL_EN = "enable" callback
> 	poweroff LED unit/BL_EN = "disable" callback
> 	poweroff LCD unit/LCD_EN = "post_disable" callback

I don't like this. What happens when the next panel comes around that
has a yet slightly different requirement? Will we introduce a new
pre_pre_enable() and post_post_disable() function then?

There's got to be a better way to solve this.

Thierry

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