RFC: Where to store camera properties (upside down, needs sw whitebalance, etc). ?

Quoted 10 lines

Quoted 10 lines

2) With some cams the upside down ness may actually be stored in an eeprom, or in some cases even determined by a switch (so the cam can be rotated manually by the user and the the switch indicates the position)

In these cases we need a userspace API to find this out too. Since this is a per frame thing for some cams (one frame could be upright, the next upside down). I would like to suggest to define some V4L2_BUF_FLAG_ 's for this which can be used by drivers to indicate that the picture in the buffer is vflipped or hflipped (with upside down being both together).

Please be aware of the fact that, when the gspca-sq905 module is considered complete, there will need to be some kind of scheme which will take its needs into consideration. Here is what happens with these cameras:

1. All of them have the same Vendor:Product number, 0x2770:0x9120.

2. Some of them emit output which needs vertical inversion, but for some others a horizontal mirroring is required, instead.

3. The way that you can tell which is needed is that a four-byte model number is requested, and that can be parsed to decide which of (1) or
(2) to do. The way the camera works, the first step in initializing it is to read this number; the streaming takes place after that.

Clearly, it is possible either to perform the appropriate action on the frames either in the module, or in userspace, in libv4l. Equally obvious, if the action has to take place in userspace then there has to be some way to pass the appropriate information on.

From my point of view, it does not matter whether the appropriate manipulations take place in the module or in userspace. I merely want to point out that the information does not come from the Vendor:Product number, but from a specific query which takes place after the module is in control and is sending commands to the camera. And, if the manipulation is done in userspace then the information has to be passed on, too.

Theodore Kilgore

The use of the buffer flags makes the life easier as this flag is read for every image. So we can solve for the flip/rotation issues with the help of two new buffer flags: V4L2_BUF_FLAG_NEEDS_HFLIP and V4L2_BUF_FLAG_NEEDS_VFLIP.

A driver has to set them properly. Does the rotation or flip(s) apply to every image (e.g. sensor upside down) or change with frames (e.g. Genesys webcams), that no more matters .
I can do the patch these days.
I do not remember if there is h/v flip functions in the libv4l, maybe they have to be added.

Regards,
Nol