linux-kernel - Re: [PATCH v2 1/8] media: v4l: ctrls: add a control for flash/strobe duration

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Message-ID: <Z9P01zU_Kg0U62wa@kekkonen.localdomain>
Date: Fri, 14 Mar 2025 09:20:23 +0000
From: Sakari Ailus <sakari.ailus@...ux.intel.com>
To: Richard Leitner <richard.leitner@...ux.dev>
Cc: Dave Stevenson <dave.stevenson@...pberrypi.com>,
	Mauro Carvalho Chehab <mchehab@...nel.org>,
	Lee Jones <lee@...nel.org>, Pavel Machek <pavel@...nel.org>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-leds@...r.kernel.org
Subject: Re: [PATCH v2 1/8] media: v4l: ctrls: add a control for flash/strobe
 duration

Hi Richard,

Thanks for the set.

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.

> 
> Signed-off-by: Richard Leitner <richard.leitner@...ux.dev>
> ---
>  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