Hi, quoting V4L2 spec: http://v4l2spec.bytesex.org/spec/r13317.htm "__s32 step [...] Generally drivers should not scale hardware control values. It may be necessary for example when the name or id imply a particular unit and the hardware actually accepts only multiples of said unit. If so, drivers must take care values are properly rounded when scaling, such that errors will not accumulate on repeated read-write cycles."
I'm wondering what that "particular unit" means. Is it OK to name V4L2_CID_EXPOSURE to "Exposure time [us]" and then use microseconds for exposure time, even if HW supports only image row granularity (rolling shutter)? If not, how should the driver report to user program the actual exposure time (necessary eg. for 50 Hz/60 Hz flicker elimination). What about flash timeout, we have here a circuit which supports only 50, 100, 200, 400, etc. milliseconds. I report "step" to be 50 ms and then round the user setting to the closest value available. User program could query the actual value used with VIDIOC_G_CTRL. The same problem holds for other controls, at least we'd like to use exposure value (EV) units for gain, etc. - Tuukka -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
