Hi Hans, On Fri, Apr 26, 2024 at 10:12:37AM +0200, Hans Verkuil wrote: > On 4/26/24 09:39, Sakari Ailus wrote: > > Hi Hans, > > > > On Fri, Apr 26, 2024 at 09:22:40AM +0200, Hans Verkuil wrote: > >> On 20/02/2024 14:03, Sakari Ailus wrote: > >>> When a device passes through the video data while still having its own > >>> receiver and transmitter, it can use the same frequency as the upstream > >>> link does. The Intel MEI CSI device is an example of this. An integer menu > >>> control isn't useful in conveying the actual frequency to the receiver in > >>> this case. > >>> > >>> Document that the LINK_FREQ control may also be a 64-bit integer control. > >>> > >>> Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> > >>> --- > >>> .../userspace-api/media/v4l/ext-ctrls-image-process.rst | 2 +- > >>> 1 file changed, 1 insertion(+), 1 deletion(-) > >>> > >>> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst > >>> index b1c2ab2854af..7a3ccb100e1d 100644 > >>> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst > >>> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst > >>> @@ -22,7 +22,7 @@ Image Process Control IDs > >>> > >>> .. _v4l2-cid-link-freq: > >>> > >>> -``V4L2_CID_LINK_FREQ (integer menu)`` > >>> +``V4L2_CID_LINK_FREQ (integer menu or 64-bit integer)`` > >>> The frequency of the data bus (e.g. parallel or CSI-2). > >> > >> I really think a new control should be created for this. > >> > >> As I understand it, V4L2_CID_LINK_FREQ gives a set of supported frequencies, > >> and the application has to pick one (I think?). Is it supposed to be a > >> read-only control? Some driver seem to set the READ_ONLY flag, and some do not. > >> The documentation isn't helpful in that respect. > > > > This is read-only effectively in current IVSC implementation. > > > >> > >> In the case of the Intel MEI CSI and similar devices a new control would be > >> better, I think. Do I understand it correctly that for these devices it would > >> always be a read-only control? I.e. it just reports the frequency, but applications > >> cannot change it? > > > > How would you call the new control? > > > > V4L2_CID_LINK_FREQ_READ_ONLY? > > > > Originally the reason for changing LINK_FREQ for sensors was be part of > > changing sensor's configuration to achieve a given frame interval. > > Will this new variant always be read-only? At least for this purpose I think so. Apart from the sensor configuration, I'm not aware of another use case for the user to change it. > > How about V4L2_CID_CUR_LINK_FREQ? > > I.e., it returns the current link frequency. That way it can also be > used by drivers that implement V4L2_CID_LINK_FREQ. It could, but the drivers already report this using V4L2_CID_LINK_FREQ. It'd be extra driver code for little if any gain. > > Better ideas are welcome :-) V4L2_CID_LINK_FREQ_VALUE? V4L2_CID_LINK_FREQ2?? :-) -- Regards, Sakari Ailus
