linux-kernel - Re: [PATCH v4 19/19] auxdisplay: ht16k33: Add LED support

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Message-ID: <5b70f272-eec9-0ff7-1bd2-bf1659b10e9c@infradead.org>
Date:   Tue, 27 Jul 2021 14:05:05 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Robin van der Gracht <robin@...tonic.nl>,
        Rob Herring <robh+dt@...nel.org>,
        Miguel Ojeda <ojeda@...nel.org>,
        Paul Burton <paulburton@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Pavel Machek <pavel@....cz>, Marek Behun <marek.behun@....cz>,
        Arnd Bergmann <arnd@...db.de>
Cc:     devicetree@...r.kernel.org, linux-leds@...r.kernel.org,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 19/19] auxdisplay: ht16k33: Add LED support

On 7/27/21 7:04 AM, Geert Uytterhoeven wrote:
> Instantiate a single LED based on the "led" subnode in DT.
> This allows the user to control display brightness and blinking (backed
> by hardware support) through the LED class API and triggers, and exposes
> the display color.  The LED will be named
> "auxdisplay:<color>:<function>".
> 
> When running in dot-matrix mode and if no "led" subnode is found, the
> driver falls back to the traditional backlight mode, to preserve
> backwards compatibility.
> 
> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> ---
> v4:
>   - Add missing select LEDS_CLASS,
> 
> v3:
>   - Remove unneeded C++ comment,
>   - Use "err" instead of "error" to be consistent with existing driver
>     naming style,
>   - Make the creation of the LED device dependent on the presence of the
>     "led" subnode in DT, so it can be used in dot-matrix mode too.
>   - Use led_init_data() and devm_led_classdev_register_ext() to retrieve
>     all LED properties from DT, instead of manual LED name construction
>     based on just the "color" property,
> 
> v2:
>   - Use "auxdisplay" instead of DRIVER_NAME in LED name.

Hi Geert,

Since LEDS_CLASS depends on NEW_LEDS, does this also need to
select NEW_LEDS?

and similar for INPUT_MATRIXKMAP: it depends on INPUT.

However, selecting (enabling) an entire subsystem is not a
preferable thing to do.

> ---
>  drivers/auxdisplay/Kconfig   |   1 +
>  drivers/auxdisplay/ht16k33.c | 124 ++++++++++++++++++++++++++++++-----
>  2 files changed, 108 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/auxdisplay/Kconfig b/drivers/auxdisplay/Kconfig
> index 42fc7b155de09dbc..7436b9a4edbe5450 100644
> --- a/drivers/auxdisplay/Kconfig
> +++ b/drivers/auxdisplay/Kconfig
> @@ -176,6 +176,7 @@ config HT16K33
>  	select FB_SYS_IMAGEBLIT
>  	select INPUT_MATRIXKMAP
>  	select FB_BACKLIGHT
> +	select LEDS_CLASS
>  	select LINEDISP
>  	help
>  	  Say yes here to add support for Holtek HT16K33, RAM mapping 16*8

thanks.
-- 
~Randy