linux-kernel - Re: [PATCH net-next,v2 1/2] net: phy: add LED dimming support

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Message-ID: <11bb4bcf-c3e6-4ab0-b61c-ef7f37dd695c@lunn.ch>
Date: Sat, 5 Apr 2025 21:45:04 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Aleksander Jan Bajkowski <olek2@...pl>
Cc: lxu@...linear.com, hkallweit1@...il.com, linux@...linux.org.uk,
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, lee@...nel.org,
	linux-leds@...r.kernel.org, Daniel Golle <daniel@...rotopia.org>
Subject: Re: [PATCH net-next,v2 1/2] net: phy: add LED dimming support

On Sat, Apr 05, 2025 at 09:09:53PM +0200, Aleksander Jan Bajkowski wrote:
> Some PHYs support LED dimming. The use case is a router that dims LEDs
> at night. PHYs from different manufacturers support a different number of
> brightness levels, so it was necessary to extend the API with the
> led_max_brightness() function. If this function is omitted, a default
> value is used, assuming that only two levels are supported.
> 
> Signed-off-by: Aleksander Jan Bajkowski <olek2@...pl>
> Reviewed-by: Daniel Golle <daniel@...rotopia.org>

The merge window is still open at the moment, so you will need to
repost next week.


> ---
>  drivers/net/phy/phy_device.c | 7 ++++++-
>  include/linux/phy.h          | 7 +++++++
>  2 files changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index 675fbd225378..4011ececca70 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -3106,7 +3106,12 @@ static int of_phy_led(struct phy_device *phydev,
>  
>  	cdev->hw_control_get_device = phy_led_hw_control_get_device;
>  #endif
> -	cdev->max_brightness = 1;
> +	if (phydev->drv->led_max_brightness)
> +		cdev->max_brightness =
> +			phydev->drv->led_max_brightness(phydev, index);
> +	else
> +		cdev->max_brightness = 1;

> +	/**
> +	 * @led_max_brightness: Maximum number of brightness levels
> +	 * supported by hardware. When only two levels are supported
> +	 * i.e. LED_ON and LED_OFF the function can be omitted.
> +	 */
> +	int (*led_max_brightness)(struct phy_device *dev, u8 index);

We might want to consider types here. led_classdev->max_brightness is
an unsigned int. Your callback returns int, so it could include
-EOPNOTSUPP, -EINVAL, -ENODEV etc. There is no check for an error
code, so max_brightness is going to end up ~ 2^32, and not work very
well.

	Andrew