From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756644AbaIQTXm (ORCPT ); Wed, 17 Sep 2014 15:23:42 -0400 Received: from rhlx01.hs-esslingen.de ([129.143.116.10]:54618 "EHLO rhlx01.hs-esslingen.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756450AbaIQTXk (ORCPT ); Wed, 17 Sep 2014 15:23:40 -0400 Date: Wed, 17 Sep 2014 21:23:37 +0200 From: Andreas Mohr To: Takashi Iwai Cc: Dmitry Torokhov , Clemens Ladisch , Andreas Mohr , Vojtech Pavlik , Jiri Kosina , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] Input: joystick - Use ktime for measuring timing Message-ID: <20140917192337.GA27319@rhlx01.hs-esslingen.de> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Priority: none User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Wed, Sep 10, 2014 at 05:57:17PM +0200, Takashi Iwai wrote: > The current codes in gameport and analog joystick drivers for the time > accounting have a long-standing problem when the system is running > with CPU freq; since the timing is measured via TSC or sample counter, > the calculation isn't reliable. Thank you very much for having followed through on this! (somehow you never seem to disappoint me :) While working on testing this and doing various gameport/soundcard modifications, I'm afraid I have seen the following checkpatch.pl (of v3.16) warnings: WARNING: Missing a blank line after declarations #164: FILE: drivers/input/joystick/analog.c:192: + unsigned int x; + GET_TIME(x); WARNING: line over 80 characters #224: FILE: drivers/input/joystick/analog.c:301: + port->axes[j] = (delta(start, time[i]) << ANALOG_FUZZ_BITS) / port->loop; BTW the commit as-is will not be compatible with v3.16 since there's no ktime_get_ns() there yet and (to add insult to injury) even the #include header files have changed, too. That's a bit of a pity since I just had intended to say that it's a very good idea to release a quick(&dirty) initial timing hotfix for gameport handling *prior* to possibly doing any subsequent less-related gameport cleanup commits, since the quick initial timing hotfix would be very prominent -stable material, except it... ain't so (--> life sucks :-). So, for -stable reasons it might be very worthwhile to add some compat code to the analog.c patch - I am currently using the following compat fix (on v3.16): --- a/drivers/input/joystick/analog.c +++ b/drivers/input/joystick/analog.c @@ -36,7 +36,14 @@ #include #include #include -#include +//#include +#include + +static inline u64 ktime_get_ns(void) +{ + return ktime_to_ns(ktime_get()); +} + (which obviously isn't fit for purpose yet since you'd need a versioned #include conditional, and the name of this function when unconditionally added is in direct conflict with the same-name > v3.16 one) So, should that commit be improved to have a simple versioning check in order to be fully -stable deployable, or would -stable be handled differently anyway? (I'll now have these updates and checkpatch.pl stuff maintained in a FIXUP commit locally) So much for a quick status update (I'll be rebooting into 3.16 now - my last kernel build was as low as 3.11.x even, WOW). Thanks, Andreas Mohr