On 01/31/2018 05:51 AM, Tim Harvey wrote: > On Mon, Jan 29, 2018 at 4:00 AM, Hans Verkuil <hverkuil@xxxxxxxxx> wrote: >> On 01/25/2018 05:15 PM, Tim Harvey wrote: > <snip> >>>> >>>> Hmm. This receiver supports multiple output formats, but you advertise only one. >>>> That looks wrong. If nothing else, you should be able to switch between RGB and >>>> YUV 4:4:4 since they use the same port config. >>>> >>>> It's a common use-case that you want to switch between RGB and YUV depending on >>>> the source material (i.e. if you receive a desktop/graphics then RGB is best, if >>>> you receive video then YUV 4:2:2 or 4:2:0 is best). >>>> >>>> Hardcoding just one format won't do. >>>> >>> >>> I've been thinking about this a bit. I had hard-coded a single format >>> for now because I haven't had any good ideas on how to deal with the >>> fact that the port mappings would need to differ if you change from >>> the RGB888/YUV444 (I think these are referred to as 'planar' formats?) >>> to YUV422 (semi-planar) and BT656 formats. It is true though that the >>> 36bit (TDA19973) RGB888/YUV444 and 24bit (TDA19971/2) formats can both >>> be supported with the same port mappings / pinout. >> >> Regarding terminology: >> >> RGB and YUV are typically interleaved, i.e. the color components are >> (for two pixels) either RGBRGB for RGB888, YUVYUV for YUV444 or YUYV >> for YUV422. >> >> Planar formats are in practice only seen for YUV and will first output >> all Y samples, and then the UV samples. This requires that the hardware >> buffers the frame and that's not normally done by HDMI receivers. >> >> The DMA engine, however, is often able to split up the interleaved YUV >> samples that it receives and DMA them to separate buffers, thus turning >> an interleaved media bus format to a planar memory format. >> >> BT656 doesn't refer to how the samples are transferred, instead it >> refers to how the hsync and vsync are reported. The enum v4l2_mbus_type >> has various options, one of them being BT656. >> >> Which mbus type is used is board specific (and should come from the >> device tree). Whether to transmit RGB888, YUV444 or YUV422 (or possibly >> even YUV420) is dynamic and is up to userspace since it is use-case >> dependent. >> >> So you'll never switch between BT656 and CSI, but you can switch between >> BT656+RGB and BT656+YUV, or between CSI+RGB and CSI+YUV. >> >>> >>> For example the GW5400 has a TDA19971 mapped to IMX6 CSI_DATA[19:4] >>> (16bit) for YUV422. However if you want to use BT656 you have to shift >>> the TDA19971 port mappings to get the YCbCr pins mapped to >>> CSI_DATA[19:x] and those pin groups are at the bottom of the bus for >>> the RGB888/YUV444 format. >> >> As mentioned above, you wouldn't switch between mbus types. >> >>> >>> I suppose however that perhaps for the example above if I have a 16bit >>> width required to support YUV422 there would never be a useful case >>> for supporting 8-bit/10-bit/12-bit BT656 on the same board? >> >> You wouldn't switch between mbus types, but if the device tree configures >> BT.656 with a bus width of 24 bits, then the application might very well >> want to dynamically switch between 8, 10 and 12 bits per color component. >> > > Hans, > > I just submitted a v7 with multiple format support. Your point about > bus_type being specified by dt is exactly what I needed to help make > sense of the formats. Ah, good. It took me some time as well before I realized that the confusion was in mixing up bus types and formats. > That said, I'm unsure how to properly test the enum_mbus_code() pad op > function. How do you obtain a list of valid formats on a subdev? > > I tried the following: > root@ventana:~# media-ctl -e 'tda19971 2-0048' > /dev/v4l-subdev1 > root@ventana:~# media-ctl --get-v4l2 '"tda19971 2-0048":0' > [fmt:UYVY8_2X8/1280x720 field:none colorspace:srgb] > ^^^^ calls get_format and returns the 1 and only format available for > my tda19971 with 16bit parallel bus > root@ventana:~# v4l2-ctl -d /dev/v4l-subdev1 --get-fmt-video-out > VIDIOC_G_FMT: failed: Inappropriate ioctl for device > root@ventana:~# v4l2-ctl -d /dev/v4l-subdev1 --list-formats-out > ioctl: VIDIOC_ENUM_FMT > > I'm thinking perhaps enumerating the list of possible formats is a > missing feature in media-ctl? Yeah, it is. Surprising, really. Ditto for the SUBDEV_ENUM_FRAME_SIZE/INTERVAL ioctls. I wonder whether this should be added to v4l2-ctl, media-ctl or both. I always felt that media-ctl is more about setting up the whole pipeline, whereas v4l2-ctl is specific to a V4L2 device. Regards, Hans
