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Date: Fri, 2 Feb 2024 17:30:23 +0000
From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Andrew Lunn <andrew@lunn.ch>
Cc: Christian Marangi <ansuelsmth@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Bjorn Andersson <andersson@kernel.org>,
	Konrad Dybcio <konrad.dybcio@linaro.org>,
	Heiner Kallweit <hkallweit1@gmail.com>,
	Frank Rowand <frowand.list@gmail.com>,
	Robert Marko <robert.marko@sartura.hr>, netdev@vger.kernel.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-msm@vger.kernel.org
Subject: Re: [net-next PATCH v5 9/9] net: phy: qca807x: add support for
 configurable LED
Message-ID: <Zb0mryS0CGfkolbO@shell.armlinux.org.uk>
References: <20240201151747.7524-1-ansuelsmth@gmail.com>
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 <46085abf-8e82-4fd9-95b8-95cbfde6e5c2@lunn.ch>
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 <8bbff46a-f316-49b7-82f8-44dbdd452b0d@lunn.ch>
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Sender: Russell King (Oracle) <linux@armlinux.org.uk>

On Fri, Feb 02, 2024 at 06:08:33PM +0100, Andrew Lunn wrote:
> On Fri, Feb 02, 2024 at 05:40:21PM +0100, Christian Marangi wrote:
> > On Fri, Feb 02, 2024 at 02:43:37AM +0100, Andrew Lunn wrote:
> > > > +
> > > > +			phydev->drv->led_brightness_set = NULL;
> > > > +			phydev->drv->led_blink_set = NULL;
> > > > +			phydev->drv->led_hw_is_supported = NULL;
> > > > +			phydev->drv->led_hw_control_set = NULL;
> > > > +			phydev->drv->led_hw_control_get = NULL;
> > > 
> > > I don't see how that works. You have multiple PHYs using this
> > > driver. Some might have LEDs, some might have GPOs. But if you modify
> > > the driver structure like this, you prevent all PHYs from having LEDs,
> > > and maybe cause a Opps if a PHY device has already registered its
> > > LEDs?
> > >
> > 
> > God you are right! Off-topic but given the effects this may cause, why
> > the thing is not const?
> 
> I would like it to be, but its not easy. There are fields in the
> driver structure that phylib needs to modify. e.g. mdiodrv.driver gets
> passed to the driver core when registering the driver, and it modifies
> it. mdiodrv.flags is also manipulated. So we cannot make the whole
> structure const.

We can make phy_device's drv pointer const though, which would have the
effect of catching code such as the above. That doesn't impact the
driver model nor the mdio layer.

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