Hi Jacopo, On Tue, Jul 04, 2023 at 05:00:24PM +0200, Jacopo Mondi wrote: > Hi Tommaso > > On Tue, Jul 04, 2023 at 04:30:09PM +0200, Tommaso Merciai wrote: > > Hi Jacopo, > > > > On Tue, Jul 04, 2023 at 04:05:44PM +0200, Jacopo Mondi wrote: > > > Hi Tommaso > > > > > > On Tue, Jul 04, 2023 at 03:51:43PM +0200, Tommaso Merciai wrote: > > > > Hi Jacopo, > > > > > > > > On Mon, Jul 03, 2023 at 10:29:10PM +0200, Jacopo Mondi wrote: > > > > > Document the suggested way to exposure controls for exposure and gain > > > > > for camera sensor drivers. > > > > > > > > > > Signed-off-by: Jacopo Mondi <jacopo.mondi@xxxxxxxxxxxxxxxx> > > > > > --- > > > > > .../driver-api/media/camera-sensor.rst | 19 +++++++++++++++++++ > > > > > 1 file changed, 19 insertions(+) > > > > > > > > > > diff --git a/Documentation/driver-api/media/camera-sensor.rst b/Documentation/driver-api/media/camera-sensor.rst > > > > > index ee4a7fe5f72a..dfe8f35aecea 100644 > > > > > --- a/Documentation/driver-api/media/camera-sensor.rst > > > > > +++ b/Documentation/driver-api/media/camera-sensor.rst > > > > > @@ -189,3 +189,22 @@ the ``V4L2_CID_VFLIP`` and ``V4L2_CID_HFLIP`` controls with the > > > > > a flip can potentially change the output buffer content layout. Flips should > > > > > also be taken into account when enumerating and handling media bus formats > > > > > on the camera sensor source pads. > > > > > + > > > > > +Exposure and Gain Control > > > > > +------------------------- > > > > > + > > > > > +Camera sensor drivers that allows applications to control the image exposure > > > > > +and gain should do so by exposing dedicated controls to applications. > > > > > + > > > > > +Exposure time is controlled by registering the ``V4L2_CID_EXPOSURE`` control. > > > > > +The control definition does not specify a unit to allow maximum flexibility > > > > > +for multiple device types, but when used for camera sensor driver it should be > > > > > > > > > +expressed in unit of lines whenever possible. > > > > > > > > Same comment here. > > > > > > I might have missed what other comment you are referring to :) > > > > Sorry, I'm referring to your comment: > > > > "I think this might be useful yes. A few paragraph above the frame > > duration calculation formula is expressed as well, so I guess adding > > one for this is helpful too" > > > > Ah ok, see v2 for that > > > > > > > > > > > > Can you add formula/references about this point I think you are referring on "tline" units (maybe I'm completely wrong :) ), > > > > > > Is "tline" the line duration ? If that's the case then no, I am > > > referring to the number of lines, not their duration. > > > > Ok. Thanks, need to find some docs regarding this units :'( > > For this I think having some good reference/formula here would help users to find the > > corrispective value into the sensor datasheet. > > > > I'm still not sure if you're talking about the formula to convert from > a time duration to the number of lines as Dave suggested (which I > added in v2) This one. I checked v2 thanks for the clarification! Regards, Tommaso > or a formula to convert from the number of lines provided > by userspace as the value of the V4L2_CID_EXPOSURE control to the > actual value to be set in the sensor's registers that control the > exposure time. If you're referring to the latter I'm afraid this is > device specific and putting any example here might actually be > mis-leading. As far as I can tell the sensors I had dealt with, > internally represents the exposure control in number of lines or > fractions of lines. Doing the conversion in the driver is usually > trivial (I'm sure there are devices where this is less trivial of > course). > > Did I get your question right or am I still missing something ? > > > I just proved this to you :) > > > > Regards, > > Tommaso > > > > > > > > > but to be honest checking also the some sensors datasheet I don't find to much infos about this units. > > > > Would be really helpfull to add some details on this point. > > > > > > > > > + > > > > > +Camera sensor driver should try whenever possible to distinguish between the > > > > > +analogue and digital gain control functions. Analogue gain is a multiplier > > > > > +factor applied to all color channels on the pixel array before they get > > > > > +converted in the digital domain. It should be be made controllable by > > > > > +registering the ``V4L2_CID_ANALOGUE_GAIN`` control, expressed as a device > > > > > +specific gain code. Digital gain control is optional and should be exposed to > > > > > +applications by registering ``V4L2_CID_DIGITAL_GAIN``. Camera sensor drivers are > > > > > -- > > > > > > > > This part looks good to me. > > > > > > > > Thanks, > > > > Tommaso > > > > > > > > > 2.40.1 > > > > >
