linux-kernel - Re: [PATCH] userspace API definitions for auto-focus coil

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Date:	Mon, 6 Jun 2016 09:06:29 +0300
From:	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>
To:	Pavel Machek <pavel@....cz>, Sakari Ailus <sakari.ailus@....fi>
Cc:	pali.rohar@...il.com, sre@...nel.org,
	kernel list <linux-kernel@...r.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	linux-omap@...r.kernel.org, tony@...mide.com, khilman@...nel.org,
	aaro.koskinen@....fi, patrikbachan@...il.com, serge@...lyn.com,
	linux-media@...r.kernel.org, mchehab@....samsung.com,
	robh+dt@...nel.org, pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH] userspace API definitions for auto-focus coil

Hi,

On  5.06.2016 22:07, Pavel Machek wrote:
> Add userspace API definitions.
>
> Signed-off-by: Pavel Machek <pavel@....cz>
>
> diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
> index b6a357a..23011cc 100644
> --- a/include/uapi/linux/v4l2-controls.h
> +++ b/include/uapi/linux/v4l2-controls.h
> @@ -974,4 +975,9 @@ enum v4l2_detect_md_mode {
>   #define V4L2_CID_DETECT_MD_THRESHOLD_GRID	(V4L2_CID_DETECT_CLASS_BASE + 3)
>   #define V4L2_CID_DETECT_MD_REGION_GRID		(V4L2_CID_DETECT_CLASS_BASE + 4)
>
> +/* Control IDs specific to the AD5820 driver as defined by V4L2 */
> +#define V4L2_CID_FOCUS_AD5820_BASE 	(V4L2_CTRL_CLASS_CAMERA | 0x10af)
> +#define V4L2_CID_FOCUS_AD5820_RAMP_TIME	(V4L2_CID_FOCUS_AD5820_BASE+0)
> +#define V4L2_CID_FOCUS_AD5820_RAMP_MODE	(V4L2_CID_FOCUS_AD5820_BASE+1)
> +
>   #endif
>

Sakari, what about adding those as standard camera controls? It seems 
ad5820 is not the only VCM driver to implement "antiringing" controls, 
http://rohmfs.rohm.com/en/products/databook/datasheet/ic/motor/mobile_module/bu64241gwz-e.pdf 
is another example I found by quick search.

What about:

#define V4L2_CID_FOCUS_STEP_MODE xxx
enum v4l2_cid_focus_step_mode {
V4L2_CID_FOCUS_STEP_MODE_DIRECT,
V4L2_CID_FOCUS_STEP_MODE_LINEAR,
V4L2_CID_FOCUS_STEP_MODE_AUTO
};
#define V4L2_CID_FOCUS_STEP_TIME xxx+1

Also, how the userspace(or the kernel) is notified by v4l that there is 
an event? The point is - I think it is a good idea to notify when VCM 
has completed its movement, we can start a timer based on the current 
position, mode, step time etc and notify after the pre-calculated 
movement time.

Here ftp://ftp.analog.com/pub/evalcd/AD5820_v1_0/AD5820_Quickstart.pdf 
can be found the modes/timings description for ad5820 along with the 
equations needed to calculate timings etc.

Ivo