Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755390AbbBFNra (ORCPT ); Fri, 6 Feb 2015 08:47:30 -0500 Received: from hofr.at ([212.69.189.236]:36640 "EHLO mail.hofr.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752561AbbBFNr2 (ORCPT ); Fri, 6 Feb 2015 08:47:28 -0500 Date: Fri, 6 Feb 2015 14:47:26 +0100 From: Nicholas Mc Guire To: Thomas Winischhofer Cc: Tormod Volden , Scot Doyle , Nicholas Mc Guire , Jean-Christophe Plagniol-Villard , Tomi Valkeinen , linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH RFC] video: fbdev: sis: condition with no effect Message-ID: <20150206134726.GB32696@opentech.at> References: <1423049774-16305-1-git-send-email-hofrat@osadl.org> <54D46694.7050108@winischhofer.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54D46694.7050108@winischhofer.net> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4814 Lines: 103 On Fri, 06 Feb 2015, Thomas Winischhofer wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > Tormod Volden wrote: > > On Thu, Feb 5, 2015 at 9:45 PM, Scot Doyle wrote: > >> On Wed, 4 Feb 2015, Nicholas Mc Guire wrote: > >>> The if and the else branch code are identical - so the condition has no > >>> effect on the effective code - this patch removes the condition and the > >>> duplicated code. > >>> > >>> Signed-off-by: Nicholas Mc Guire > >>> --- > >>> > >>> This code has been in here since commit 544393fe584d ("sisfb update") so I guess it is > >>> safe to simply remove the duplicated code if nobody noticed for 10 years. > >>> > >>> Note that the code is not really CodingStyle compliant - the lines inserted were formatted > >>> to satisfy the coding style but I'm unsure if it is not better to leave it in the > >>> old format. > >>> > >>> Patch was only compile tested with x86_64_defconfig + > >>> CONFIG_FB_SIS=m, CONFIG_FB_SIS_300=y, CONFIG_FB_SIS_315=y > >>> > >>> Patch is against 3.19.0-rc7 (localversion-next is -next-20150204) > >>> > >>> drivers/video/fbdev/sis/init301.c | 9 ++------- > >>> 1 file changed, 2 insertions(+), 7 deletions(-) > >>> > >>> diff --git a/drivers/video/fbdev/sis/init301.c b/drivers/video/fbdev/sis/init301.c > >>> index 295e0de..9533a8ab 100644 > >>> --- a/drivers/video/fbdev/sis/init301.c > >>> +++ b/drivers/video/fbdev/sis/init301.c > >>> @@ -7971,13 +7971,8 @@ SiS_SetCHTVReg(struct SiS_Private *SiS_Pr, unsigned short ModeNo, unsigned short > >>> } > >>> } else { /* ---- PAL ---- */ > >>> /* We don't play around with FSCI in PAL mode */ > >>> - if(resindex == 0x04) { > >>> - SiS_SetCH70xxANDOR(SiS_Pr,0x20,0x00,0xEF); /* loop filter off */ > >>> - SiS_SetCH70xxANDOR(SiS_Pr,0x21,0x01,0xFE); /* ACIV on */ > >>> - } else { > >>> - SiS_SetCH70xxANDOR(SiS_Pr,0x20,0x00,0xEF); /* loop filter off */ > >>> - SiS_SetCH70xxANDOR(SiS_Pr,0x21,0x01,0xFE); /* ACIV on */ > >>> - } > >>> + SiS_SetCH70xxANDOR(SiS_Pr, 0x20, 0x00, 0xEF); /* loop filter off */ > >>> + SiS_SetCH70xxANDOR(SiS_Pr, 0x21, 0x01, 0xFE); /* ACIV on */ > >>> } > >>> > >>> #endif /* 300 */ > >> The code covering the PAL case had this redundancy when it was introduced > >> in Linux 2.4.19. > >> > >> Lines 7934-7981 consider three variables: PAL, overscan, and resindex. > >> Given the "#ifdef 0" block, couldn't the current six sections collapse > >> into two? One for (!PAL && overscan && resindex==5) and another for the > >> rest? > > > > Are we sure there isn't a typo in one of the duplicate clauses? Or > > wrong copy-pasting? Generally I am skeptical to "fixing" code without > > understanding what is behind or testing it, and just cosmetically > > brush over it. For now at least it is obvious that there is something > > wrong. In case (although an unlikely one) someone who understands the > > code and knows this chip comes along, he would quickly spot this. > > After your "fixups" this will be all forgotten. Additionally it adds > > to the impression that this code is being maintained, which is wrong. > > > > I would understand an argument about annoying compiler warnings and > > the like, but in that case I would prefer to #if 0 it instead of > > "prettifying" it. > > > > 0.02 > > Tormod > > > > The code is partly unfinished due to a lack of hardware to test this > with. SiS announced SiS+Chrontel 7019 combos at some point but I have > never seen one. The code was written based on the Chrontel datasheets, > which weren't clear to some extent, and there wasn't ever any test > hardware. I don't recall this one exactly, but identical if-else > statements mean that one alternative is (assumingly) correct, while the > other is uncertain and/or untested. I left such redunant if-statements > in the code to remember the conditions and the fact that there is a > second alternative. > > Considering the long time I'd say it's safe to simplify this. > > A word on other changes I monitored recently: Please bear in mind that > with video hardware reading and writing registers is not simple like > reading and writing to memory. Sometimes reading causes an effect in the > hardware as well (latches, etc), so removing seemingly redundant > GetReg/SetReg sequences might actually have an effect. > thanks for that note - will add that to my checklist of sideffects for future patches. thx! hofrat -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/