Hi Richard, On Fri, Mar 14, 2025 at 11:25:09AM +0100, Richard Leitner wrote: > On Fri, Mar 14, 2025 at 09:20:23AM +0000, Sakari Ailus wrote: > > Hi Richard, > > > > Thanks for the set. > > Hi Sakari, > thanks for the quick response! > > > > > On Fri, Mar 14, 2025 at 09:49:55AM +0100, Richard Leitner wrote: > > > Add a control V4L2_CID_FLASH_DURATION to set the duration of a > > > flash/strobe pulse. This is different to the V4L2_CID_FLASH_TIMEOUT > > > control, as the timeout defines a limit after which the flash is > > > "forcefully" turned off again. > > > > > > On the other hand the new V4L2_CID_FLASH_DURATION is the desired length > > > of the flash/strobe pulse > > > > What's the actual difference between the two? To me they appear the same, > > just expressed in a different way. > > According to FLASH_TIMEOUT documentation: > > Hardware timeout for flash. The flash strobe is stopped after this > period of time has passed from the start of the strobe. [1] > > This is a little bit unspecific, but as also discussed with Dave [2] > according to the documentation of V4L2_FLASH_FAULT_TIMEOUT it seems to > be targeted at providing a "real timeout" control, not settings the > desired duration: > > The flash strobe was still on when the timeout set by the user > --- V4L2_CID_FLASH_TIMEOUT control --- has expired. Not all flash > controllers may set this in all such conditions. [1] > > If I understood that wrong, I'm also happy to use FLASH_TIMEOUT for this > use-case. But tbh I think FLASH_DURATION would be more specific. > > As this still seems unclear: Should the documentation be > changed/rewritten if we stick with the FLASH_DURATION approach? > > [1] https://www.kernel.org/doc/html/latest/userspace-api/media/v4l/ext-ctrls-flash.html > [2] https://lore.kernel.org/lkml/CAPY8ntB8i4OyUWAL8k899yUd5QsRifJXiOfWXKceGQ7TNZ4OUw@xxxxxxxxxxxxxx/ Right, I think I can see what you're after. How does the sensor determine when to start the strobe, i.e. on which frame and which part of the exposure of that frame? > > > > > > > > > Signed-off-by: Richard Leitner <richard.leitner@xxxxxxxxx> > > > --- > > > drivers/media/v4l2-core/v4l2-ctrls-defs.c | 1 + > > > include/uapi/linux/v4l2-controls.h | 1 + > > > 2 files changed, 2 insertions(+) > > > > > > diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c b/drivers/media/v4l2-core/v4l2-ctrls-defs.c > > > index 1ea52011247accc51d0261f56eab1cf13c0624a0..f9ed7273a9f3eafe01c31b638e1c8d9fcf5424af 100644 > > > --- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c > > > +++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c > > > @@ -1135,6 +1135,7 @@ const char *v4l2_ctrl_get_name(u32 id) > > > case V4L2_CID_FLASH_FAULT: return "Faults"; > > > case V4L2_CID_FLASH_CHARGE: return "Charge"; > > > case V4L2_CID_FLASH_READY: return "Ready to Strobe"; > > > + case V4L2_CID_FLASH_DURATION: return "Strobe Duration"; > > > > > > /* JPEG encoder controls */ > > > /* Keep the order of the 'case's the same as in v4l2-controls.h! */ > > > diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h > > > index 974fd254e57309e6def95b4a4f8e4de13a3972a7..80050cadb8377e3070ebbadc493fcd08b2c12c0b 100644 > > > --- a/include/uapi/linux/v4l2-controls.h > > > +++ b/include/uapi/linux/v4l2-controls.h > > > @@ -1173,6 +1173,7 @@ enum v4l2_flash_strobe_source { > > > > > > #define V4L2_CID_FLASH_CHARGE (V4L2_CID_FLASH_CLASS_BASE + 11) > > > #define V4L2_CID_FLASH_READY (V4L2_CID_FLASH_CLASS_BASE + 12) > > > +#define V4L2_CID_FLASH_DURATION (V4L2_CID_FLASH_CLASS_BASE + 13) > > > > > > > > > /* JPEG-class control IDs */ > > > > > -- Regards, Sakari Ailus
