Andy Walls wrote: > On Sun, 2010-02-21 at 23:07 -0500, Devin Heitmueller wrote: >> I am doing some work on the saa711x driver, and ran into a case where >> I need to disable the chroma AGC and manually set the chroma gain. > > Sakari, Hans, or anyone else, > > On a somewhat related note, what is the status of the media controller > and of file handles per v4l2_subdev. Will Sakari's V4L file-handle > changes be all we need for the infrastructure or is there more to be > done after that? > > I'd like to implement specific "technician controls", something an > average user wouldn't use, for a few subdevs. The exposition of a control to the user or not is a decision of the userspace software developer. We shouldn't be too concerned about it. Eventually, we can group some controls on a "raw hardware level" group. I don't think we need a media controller for it. Also, this won't avoid developers to use the media controller to expose such controls to userspace. >> I see there is an existing boolean control called V4L2_CID_CHROMA_AGC, >> which would be the logical candidate for allowing the user to disable >> the chroma AGC. However, once this is done I still need to expose the >> ability to set the gain manually (bits 6-0 of register 0x0f). >> >> Is there some existing control I am just missing? Or do I need to do >> this through a private control. >> >> I'm asking because it seems a bit strange that someone would introduce >> a v4l2 standard control to disable the AGC but not have the ability to >> manually set the gain once it was disabled. > > Devin, > > Well, I can imagine letting hardware do the initial AGC, and then when > it is settled manually disabling it to prevent hardware from getting > "fooled". I did some tests on it with cx23881/cx23883 chips. At least on cx88, as far as I remember, the AGC doesn't affect the saturation register, so, this trick won't work. The issue with cx88 chips is that, with some video input sources, the AGC over-saturates the color pattern. So, depending on the analog video standard and the quality of the source (TV or Composite/Svideo), it gives more reallistic colors with different AGC/saturation configuration. 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
