Hi, I'm working on AR0521 MIPI camera sensor driver update and I'm still not sure how the timings should be programmed. V4L2 has: - V4L2_CID_LINK_FREQ I understand it's a menu with fixed integers (frequencies in Hz). Documentation/driver-api/media/camera-sensor.rst: "For camera sensors that are connected to a bus where transmitter and receiver require common configuration set by drivers, such as CSI-2 or parallel (BT.601 or BT.656) bus, the ``V4L2_CID_LINK_FREQ`` control is mandatory on transmitter drivers. Receiver drivers can use the ``V4L2_CID_LINK_FREQ`` to query the frequency used on the bus." How (and if) do I use the above when the sensor in question uses PLLs and can generate arbitrary link frequencies? - V4L2_CID_VBLANK and V4L2_CID_HBLANK These are fine for setting the timings (and the AR0521 can use them). There is, however, another value needed for precise timing control, the so called "extra" timing (a hw register), specified in pixels. The calculated frame rate is thus: fr = pixel_clock / (width + hblank) * (height + vblank) + extra. How do I specify the "extra"? Currently, I'm using the [sg]_frame_interval() functions, should it stay this way (so there are [HV]BLANK controls AND [sg]_frame_interval() in parallel on the same device)? It appears the userspace should be able to set, in addition to *BLANK, the pixel clock. How do I do that? The V4L2_CID_PIXEL_RATE appears to be a good candidate, but v4l2_ctrl_fill() sets a read-only flag on it. Any ideas? At present I'm about to use two (orthogonal) interfaces (frame interval based and the - incomplete - [hv]blank-based) - but perhaps I'm missing something important? -- Krzysztof Hałasa Sieć Badawcza Łukasiewicz Przemysłowy Instytut Automatyki i Pomiarów PIAP Al. Jerozolimskie 202, 02-486 Warszawa
