On Wednesday 22 October 2014 19:10:05 Guenter Roeck wrote: > 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
Ok, are you going to fix i8k_get_temp() function (with sleeping)? -- Pali Rohár pali.ro...@gmail.com
signature.asc
Description: This is a digitally signed message part.
