linux-kernel - Re: [PATCH net-next] net: phy: intel-xway: add support for PHY LEDs

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Message-ID: <ZwZ31IkwY-bum7T0@makrotopia.org>
Date: Wed, 9 Oct 2024 13:32:20 +0100
From: Daniel Golle <daniel@...rotopia.org>
To: Andrew Lunn <andrew@...n.ch>
Cc: Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] net: phy: intel-xway: add support for PHY LEDs

On Wed, Oct 09, 2024 at 02:16:29PM +0200, Andrew Lunn wrote:
> > +static int xway_gphy_led_polarity_set(struct phy_device *phydev, int index,
> > +				      unsigned long modes)
> > +{
> > +	bool active_low = false;
> > +	u32 mode;
> > +
> > +	if (index >= XWAY_GPHY_MAX_LEDS)
> > +		return -EINVAL;
> > +
> > +	for_each_set_bit(mode, &modes, __PHY_LED_MODES_NUM) {
> > +		switch (mode) {
> > +		case PHY_LED_ACTIVE_LOW:
> > +			active_low = true;
> > +			break;
> > +		case PHY_LED_ACTIVE_HIGH:
> > +			break;
> > +		default:
> > +			return -EINVAL;
> > +		}
> > +	}
> > +
> > +	return phy_modify(phydev, XWAY_MDIO_LED, XWAY_GPHY_LED_INV(index),
> > +			  active_low ? XWAY_GPHY_LED_INV(index) : 0);
> 
> This does not appear to implement the 'leave it alone' option.

The framework already implements that. The function is never called with
modes == 0.
See commit 7ae215ee7bb8 net: phy: add support for PHY LEDs polarity modes:

       if (of_property_read_bool(led, "active-low"))
               set_bit(PHY_LED_ACTIVE_LOW, &modes);
       if (of_property_read_bool(led, "inactive-high-impedance"))
               set_bit(PHY_LED_INACTIVE_HIGH_IMPEDANCE, &modes);

       if (modes) {
               /* Return error if asked to set polarity modes but not supported */
               if (!phydev->drv->led_polarity_set)
                       return -EINVAL;

               err = phydev->drv->led_polarity_set(phydev, index, modes);
               if (err)
                       return err;
       }

So in case none of the LED polarity properties are set in DT, modes is 0
and hence led_polarity_set() isn't called.

I considered to change that with my suggested patch
https://patchwork.kernel.org/project/netdevbpf/patch/473d62f268f2a317fd81d0f38f15d2f2f98e2451.1728056697.git.daniel@makrotopia.org/

But it was rightously critizised for breaking existing DT which assume
LED polarity not being touched if none of the polarity properties are
present.