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? 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. Better ideas are welcome :-) Regards, Hans
