Hi everyone, Just some little comments for my use case. Hope that helps. On 20/04/2022 00:04, Guenter Roeck wrote: > On 4/19/22 14:01, Laurent Pinchart wrote: >> On Tue, Apr 19, 2022 at 12:28:06PM -0700, Guenter Roeck wrote: >>> On 4/19/22 11:24, Nicolas Dufresne wrote: >>>> Hi, >>>> >>>> adding linux-hwmon in CC for a wider feedback. >>>> >>>> Le vendredi 15 avril 2022 à 13:18 +0200, Benjamin Mugnier a écrit : >>>>> Add V4L2_CID_TEMPERATURE control to get temperature from sensor in >>>>> celsius as a volatile and read-only control, and its documentation. >>>>> Useful to monitor thermals from v4l controls for sensors that support >>>>> this. >>>> >>>> Any justification to expose a temperature sensor outside of the dedicated kernel >>>> API hwmon ? I know if may makes it harder to use, as the sensor isn't bound to >>>> the camera driver, and also the sensor may not work if the camera is not >>>> streaming. But in the end, the API in hwmon does not look that complex, and is >>>> perhaps more precise ? This sensor is able to read the temperature even if not streaming. >>>> >>>> All in all, I think we need a strong justification to implement a custom >>>> thermometer interface, something described here and documented with care to >>>> prevent abuse. I would also see opinion from folks outside of the linux-media, >>>> hence why I have CCed hwmon mailing list. >>> >>> All I can say is that this seems to be odd and a bit outside the scope of >>> v4l2. I would have expected the vgxy61 driver to register a hwmon device >>> instead. >> >> I don't have a definitive opinion yet, but as Nicolas raised the issue >> by pushing towards hwmon, I'll offer counter-arguments for the sake of >> it :-) >> >> The temperature sensor in the imaging sensor is used to measure the die >> temperature, in order to tune the noise and spectral response model of >> the imaging sensor. It's thus not a generic-purpose temperature sensor. >> If the feature were to be exposed through hwmon, userspace would need to >> associate an hwmon device to the imaging sensor V4L2 subdev (we have a >> way to do so through the MC API, it doesn't support hwmon at this point, >> but I suppose it could be added). There are also various constraints >> that tie the temperature reading to the imaging side, it could be that >> the temperature would only be readable while capturing frames. That's >> probably possible to handle too but returning an error from the >> temperature read. >> >> Code-wise, both the driver and userspace would be more complex, for very >> little practical gain (I don't dispute a theorical gain). >> > > All I can say is - not my subsystem, not my call to make. If you say this > is special and is better handled in V4L2, I'll take you by your word. > > Guenter > I'll happily implement whatever conclusion we make here. I could also drop this control for the first iteration of the driver, and come back later once a consensus is reached. Benjamin
