Re: [PATCH v2 8/9] media: i2c: ov7251: Add strobe output enable control

[Antoine Pichot <antoine.pichot@gmail.com>]

Hi,

On Tue, Oct 28, 2026, Antoine Pichot wrote:
> Alternate frames is what the Windows driver uses for face recognition
> on this hardware: its 30 and 60 fps modes write 0xaa, and a register
> dump taken during a Windows Hello sign-in on a Surface Book 2 shows the
> same. Lighting every frame (0xff, which two of its other modes use)
> would double the average emitter power. User space tells lit frames
> from dark ones by their brightness; V4L2 has no per-frame illumination
> flag yet.

Before I send v3, could you please say which of these two you prefer?

V4L2_CID_FLASH_STROBE_OE is a boolean: it turns the strobe pin on or
off. Two sensor settings then shape the signal: how long the pulse
lasts within a frame (the span, which this driver ties to the
exposure), and which frames get a pulse at all (the pattern, one bit
per frame over eight frames). V4L2 has no control for the pattern.
ov9282 writes 0xff in its common register table, a pulse on every
frame; this patch writes 0xaa, a pulse on alternate frames. Both chips
default to 0xa5, four frames in eight, so a driver has to pick one.

- when the control is on, pulse alternate frames, as in this patch;
- when the control is on, pulse every frame, like ov9282, and add a
  menu control "Strobe Frame Pattern" with "Every frame" and
  "Alternate frames", after the infrared torch mode of the Windows
  camera API (off, always on, alternating frame illumination).

Either way the pattern is one register write.

Thanks,
Antoine