Hans Verkuil wrote: >> Hans Verkuil wrote: >>> But if you have ideas to improve the core to make it easier to add pm >>> support to the drivers that need it, then I am all for it. >> IMO, the runtime pm should be supported at V4L core, but some callbacks >> are >> needed. Also, I can see some classes of PM at the core: >> >> TV standard demod and sensors only need to be powerup when streaming. > > Definitely not the demod: that's generally used to detect whether there is > a TV signal and what audio format is used. You want that also when not > streaming. I guess it can be powered down though when no files are open. This is device-specific: on some devices, the tuner provides the info (and even decode the audio carrier). Also, on some modes (e. g. radio), the demod may be turned off. >> So, I think that we'll need some callbacks to the drivers, in order to do >> the >> power management on the applicable components. The final action should be >> at >> the driver level, but supported by the core. > > I guess the essential information is: > > 1) is someone using the driver (i.e. is a device node open, which is not > necessarily limited to v4l2-type device nodes)? > 2) are we actively streaming from or to some particular input or output? > > And we probably need some easy way to detect and set the powersaving state > for each component (subdev or the main v4l2_device). krefs can be a good alternative to check device usage and enable powersaving, but we'll need some callbacks to save/restore chip register values per dev/subdev. > > I really need to research the pm stuff... > > Regards, > > Hans > >>> Regards, >>> >>> Hans >>> >>>> Thanks >>>> Guennadi >>>> --- >>>> Guennadi Liakhovetski, Ph.D. >>>> Freelance Open-Source Software Developer >>>> http://www.open-technology.de/ >>>> >>> >> >> -- >> >> Cheers, >> Mauro >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-media" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> > > -- Cheers, Mauro _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
