On Mon, 23 Feb 2009, Hans Verkuil wrote: > On Sunday 22 February 2009 23:54:42 Hans de Goede wrote: > > Trent Piepho wrote: > > > On Sun, 22 Feb 2009, Hans de Goede wrote: > > >> Yes that is what we are talking about, the camera having a gravity > > >> switch (usually nothing as advanced as a gyroscope). Also the bits we > > >> are talking about are in a struct which communicates information one > > >> way, from the camera to userspace, so there is no way to clear the > > >> bits to make the camera do something. > > > > > > First, I'd like to say I agree with most that the installed orientation > > > of the camera sensor really is a different concept than the current > > > value of a gravity sensor. It's not necessary, and maybe not even > > > desirable, to handle them in the same way. > > > > > > I do not see the advantage of using reserved bits instead of controls. > > > > > > The are a limited number of reserved bits. In some structures there > > > are only a few left. They will run out. Then what? Packing > > > non-standard sensor attributes and camera sensor meta-data into a few > > > reserved bits is not a sustainable policy. > > > > > > Controls on the other card are not limited and won't run out. > > > > Yes but these things are *not* controls, end of discussion. The control > > API is for controls, not to stuff all kind of cruft in. > > I agree, these are not controls. > > There is an option to use the current status field. There are enough bits > free, that's not the problem. But the spec is explicit about the fact that > these bits apply to the current input only, and that's not true for these > new bits. We can change the spec in this regard of course, but then you > have to document each bit of the status field whether it is valid for the > current input only, or also if this isn't the current input. It's all a bit > messy. > > In addition, there are 4 reserved fields here and it is the first time in a > very long time that we actually need one. And after all, that's why they > are there in the first place. v4l2_capability: 5 of 32 cap bits left, 4 reserved words v4l2_fmtdesc: 31 flag bits, 4 reserved words v4l2_buffer: 22 flags bits, 1 reserved word v4l2_framebuffer: 25 cap bits, 26 flag bits, no reserved words v4l2_input: 4 reserved words v4l2_output: 4 reserved words v4l2_tuner: 27 cap bits, 4 reserved words > Trent does have a point that we need to be careful not to add fields without > a good reason. Choosing option 1 fits the bill, and the orientation also > fits the 'status' name. Only the sensor mount orientation is not really a > status. Although with some creative naming we might come close :-) > > Hmm, let's see: > > V4L2_IN_ST_HAS_SENSOR_INFO 0x00000010 > V4L2_IN_ST_SENSOR_HFLIPPED 0x00000020 > V4L2_IN_ST_SENSOR_VFLIPPED 0x00000040 > > V4L2_IN_ST_HAS_PIVOT_INFO 0x00001000 > V4L2_IN_ST_PIVOT_0 0x00000000 > V4L2_IN_ST_PIVOT_90 0x00002000 > V4L2_IN_ST_PIVOT_180 0x00004000 > V4L2_IN_ST_PIVOT_270 0x00006000 > V4L2_IN_ST_PIVOT_MSK 0x00006000 One of my other points what the controls include meta-data. What happens when someone has an orientation sensor with 45 degree resolution? A control would just change the step size from 90 to 45. Existing software would already know what it means. With this method you have to add: V4L2_IN_ST_HAS_PIVOT_45_INFO 0x00008000 V4L2_IN_ST_PIVOT_45 0x00010000 V4L2_IN_ST_PIVOT_135 0x00012000 V4L2_IN_ST_PIVOT_225 0x00014000 V4L2_IN_ST_PIVOT_315 0x00016000 V4L2_IN_ST_PIVOT_45_MSK 0x00016000 Interpreting the pivot bits becomes more fun now. Existing software can do nothing with these extra bits. It can tell the user nothing. Next, add camera aperture. f/0.7 to f/64 in both half stop and third stop increments. Getting low on bits already. Suppose I have just three or four sensors on my camera. That's not all that much. A typical digital camera has more than that. They're probably connected by something slow, like I2C. Maybe non-trivial calculations are needed to use the data, like most demod's SNR registers. Each time I query the input the driver must query and calculate the value of ALL the sensors. Even though I only can about one of them. Controls can be queried individually. -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
