linux-kernel - Re: [PATCH 03/19 v2] Staging: xgifb: Remove LCDA detection in xgifb

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Message-ID: <50002A76.6000609@igalia.com>
Date:	Fri, 13 Jul 2012 16:02:30 +0200
From:	Miguel Gómez <magomez@...lia.com>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	arnaud.patard@...-net.org, aaro.koskinen@....fi,
	dan.carpenter@...cle.com, devel@...verdev.osuosl.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/19 v2] Staging: xgifb: Remove LCDA detection in xgifb_probe().

El 09/07/12 20:39, Greg KH escribió:
> On Fri, Jul 06, 2012 at 12:40:38PM +0200, Miguel Gómez wrote:
>> The piece of code that checks for LCDA in xgifb_probe() just checks for some
>> register values but doesn't really do anything in response to them (the actions
>> that should be executed are commented).
>> As nothing is really being done, the code can be safely removed.
>
> Are you sure?  Some devices (foolish ones that is) need registers read
> to work properly as that is part of their start-up logic.  Yeah, it
> doesn't seem to make sense, but hardware designers usually have good
> reasons for doing this type of thing.  Or at least they think they do :)

Weird... I didn't expect that some devices might need those reads to 
work properly... I'm writing down that comment for the future ;)

> So have you tested the device after this change and it all works
> properly?  You do have this device, right?

I have an XGI Z7 card that I use for testing, and it doesn't require 
those reads to work properly, despite I don't have a Z9 or Z11 to test. 
But according to Aaro's comment, it seems that the patch is safe as 
these register reads don't have any effect.

Regards!

-- 
Miguel Gómez
Igalia - http://www.igalia.com


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