Re: [PATCH 1/5] backlight: lp8788: document sysfs attributes

Daniel Thompson
2018-01-31T11:07:27Z

On Fri, Jan 26, 2018 at 08:20:08PM +0530, Aishwarya Pant wrote:
> Add documentation for sysfs interfaces of lp8788 backlight driver by
> looking through the code and the git commit history.
>
> Signed-off-by: Aishwarya Pant <aishpant@gmail.com>
> ---
> Documentation/ABI/testing/sysfs-class-backlight-lp8788 | 10 ++++++++++
> 1 file changed, 10 insertions(+)
> create mode 100644 Documentation/ABI/testing/sysfs-class-backlight-lp8788
>
> diff --git a/Documentation/ABI/testing/sysfs-class-backlight-lp8788 b/Documentation/ABI/testing/sysfs-class-backlight-lp8788
> new file mode 100644
> index 000000000000..c0e565c8d63d
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-class-backlight-lp8788
> @@ -0,0 +1,10 @@
> +sysfs interface for Texas Instruments lp8788 mfd backlight driver
> +-----------------------------------------------------------------
> +
> +What: /sys/class/backlight/<backlight>/bl_ctl_mode
> +Date: Feb, 2013
> +KernelVersion: v3.10
> +Contact: Milo Kim <milo.kim@ti.com>
> +Description:
> + (RO) Displays whether the brightness is controlled by the PWM
> + input("PWM based") or the I2C register("Register based").

I rather dislike drivers with this type of "bonus" sysfs controls. I'm
struggling to come up with any reason why the userspace would want to
read this control (and I think bl_ctl_mode gets the fewest hits after
searching with google hits of any search I've tried) . It looks to me
like this is debug information that should never have gone into sysfs
at all.

So I think this is either something that should go directly into
ABI/obsolete (with a fairly short expiry time) or perhaps simply
remove the property entirely.

Daniel.