From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753714AbaJVRKR (ORCPT ); Wed, 22 Oct 2014 13:10:17 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:36068 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751031AbaJVRKP (ORCPT ); Wed, 22 Oct 2014 13:10:15 -0400 Date: Wed, 22 Oct 2014 10:10:05 -0700 From: Guenter Roeck To: Pali =?iso-8859-1?Q?Roh=E1r?= Cc: Arnd Bergmann , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Steven Honeyman Subject: Re: [PATCH] i8k: Ignore temperature sensors which report invalid values Message-ID: <20141022171005.GA30530@roeck-us.net> References: <1413730014-30945-1-git-send-email-pali.rohar@gmail.com> <201410221429.06699@pali> <20141022161947.GA31045@roeck-us.net> <201410221835.53526@pali> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <201410221835.53526@pali> User-Agent: Mutt/1.5.21 (2010-09-15) X-Authenticated_sender: guenter@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-CTCH-PVer: 0000001 X-CTCH-Spam: Unknown X-CTCH-VOD: Unknown X-CTCH-Flags: 0 X-CTCH-RefID: str=0001.0A020209.5447E4F7.006E,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0 X-CTCH-Score: 0.000 X-CTCH-ScoreCust: 0.000 X-CTCH-Rules: C_4847, X-CTCH-SenderID: linux@roeck-us.net X-CTCH-SenderID-Flags: 0 X-CTCH-SenderID-TotalMessages: 4 X-CTCH-SenderID-TotalSpam: 0 X-CTCH-SenderID-TotalSuspected: 0 X-CTCH-SenderID-TotalConfirmed: 0 X-CTCH-SenderID-TotalBulk: 0 X-CTCH-SenderID-TotalVirus: 0 X-CTCH-SenderID-TotalRecipients: 0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: mailgid no entry from get_relayhosts_entry X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 22, 2014 at 06:35:53PM +0200, Pali Rohár wrote: > On Wednesday 22 October 2014 18:19:47 Guenter Roeck wrote: > > On Wed, Oct 22, 2014 at 02:29:06PM +0200, Pali Rohár wrote: > > > On Tuesday 21 October 2014 06:27:23 Guenter Roeck wrote: > > > > On 10/20/2014 09:46 AM, Pali Rohár wrote: > > > > > Ok, I will describe my problem. Guenter, maybe you can > > > > > find another solution/fix for it. > > > > > > > > > > Calling i8k_get_temp(3) on my laptop without > > > > > I8K_TEMPERATURE_BUG always returns value 193 (which is > > > > > above I8K_MAX_TEMP). > > > > > > > > > > When I8K_TEMPERATURE_BUG is enabled (by default) then > > > > > i8k_get_temp(3) returns value from prev[3] and store new > > > > > value I8K_TEMPERATURE_BUG to prev[3]. Value in prev[3] > > > > > is initialized to 0. > > > > > > > > > > What I want to achieve is: when i8k_get_temp() for > > > > > particular sensor id always returns invalid value (> > > > > > I8K_MAX_TEMP) then we should totally ignore sensor with > > > > > that id and do not export it via hwmon. > > > > > > > > > > My solution is: initialize prev[id] to I8K_MAX_TEMP, so > > > > > on invalid data first call to i8k_get_temp(id) returns > > > > > I8K_MAX_TEMP. Then in i8k_init_hwmon check if value is > > > > > < I8K_MAX_TEMP and if not ignore sensor id. > > > > > > > > > > Guenter, it is clear now? Are you ok that we should > > > > > ignore sensor if always report value above > > > > > I8K_MAX_TEMP? If you do not like my solution/patch for > > > > > it, can you specify how other can it be fixed? > > > > > > > > I still don't see the point in initializing prev[]. > > > > > > Now prev[] is initialized to 0. It means that first call > > > i8k_get_temp() (with sensor id which return value > > > > I8K_MAX_TEMP) returns 0. Second and other calls returns > > > I8K_MAX_TEMP. > > > > > > So point is to return same value for first and other calls. > > > > Yes, I realized that after I sent my previous mail. > > > > > > Yes, I am ok with ignoring sensor values if the reported > > > > temperature is above I8K_MAX_TEMP. I am just not sure if > > > > we should check against I8K_MAX_TEMP or against, say, > > > > 192. Reason is that we do know that the sensor can > > > > erroneously return 0x99 on some systems once in a while. > > > > We would not want to ignore those sensors just because > > > > they happen to report 0x99 during initialization. > > > > > > > > So maybe make it > > > > > > > > if (err >= 0 && err < 192) > > > > > > > > and add a note before the first if(), explaining that > > > > higher values suggest that there is no sensor attached. > > > > > > > > Thanks, > > > > Guenter > > > > > > Right, now we need to decide which magic constant to use... > > > > > > And now I found another problem :-) > > > > > > On my laptop i8k_get_temp(3) not always return value 193. It > > > is only when AMD graphics card is turned off. When card is > > > on i8k_get_temp(3) returns same value as temperature hwmon > > > part from radeon DRM driver. > > > > Can you turn the GPU on or off during runtime ? > > That would make it really tricky to handle the situation. > > > > Yes. New laptops with Nvidia Optimus or AMD PowerXpress or Enduro > technology are designed to automatically turn off secondary GPU > when is not in use. And nouveau/radeon drivers together with > vga_switcheroo implements this dynamic power on/off. > > > > So it looks like that on my laptop i8k sensor with id 3 > > > reports GPU temperature. > > > > > > When card is turned off radeon driver reports -EINVAL for > > > temperature hwmon sysnode. > > > > > > So now I think i8k could not ignore sensor totally as it can > > > be mapped to some HW which can be dynamically turned on/off > > > (like my graphics card). > > > > > > So what do you think about reporting -EINVAL instead > > > I8K_MAX_TEMP when dell SMM returns value above > > > I8K_MAX_TEMP? > > > > -EINVAL is supposed to mean "Invalid Argument", so it really > > has ia different semantics. We could use -ENXIO, "No such > > device or address", which seems more appropriate. > > > > I prefer to use -EINVAL because other driver (radeon) is using it > and userspace "sensors" programs handle EINVAL and show "N/A" in > output instead reporting some error about reading value. If > nothing else consistency (with other drivers) is my argument. > Ok, if sensors implements it that way then let's do it. > > Overall, I think the entire error handling is broken and > > should be replaced. One option would be to explicitly check > > for 0x99 and, if detected, go to sleep for, say, 100ms and > > try again. If it still fails, and for all other bad values, > > return -ENXIO. Then the calling code can either return the > > error to user space in the show function, or not install the > > sensor in the probe function. > > > > Does that make sense ? > > > > Yes, replacing error handling with retry call (after some sleep) > is better then current code (which returns previous value or > returns I8K_MAX_TEMP). > > But your solution not install the sensor if probe fails on bad > value does not solve problem that i8k.ko is loading at time when > GPU card is turned off. > Yes, the dynamics in that situation makes it a bit difficult to handle the situation. > I think current check for installing sensor (err < 0) is enough > and when invalid value (> I8K_MAX_TEMP) is returned just do not > show this value for userspace in hwmon sysnode. > Ok with me, and agreed. Thanks, Guenter