netdev - Re: [PATCH net-next] net: phy: disregard "Clause 22 registers present" bit in get_phy_c45_devs_in

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Message-ID: <20190208182750.GH1853@lunn.ch>
Date:   Fri, 8 Feb 2019 19:27:50 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        David Miller <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] net: phy: disregard "Clause 22 registers
 present" bit in get_phy_c45_devs_in_pkg

> >> -	*devices_in_package |= (phy_reg & 0xffff);
> >> +	/* Bit 0 doesn't represent a device, it indicates c22 regs presence */
> >> +	*devices_in_package |= (phy_reg & 0xfffe);
> > 
> > Hi Heiner
> > 
> > Just for readability, can we use BIT(0) in there somehow?
> > 
> You think 0xfffe together with the comment is still not clear enough?

Hi Heiner

It is more i was wondering why the 0xffff was there in the first
place. PHY registers are 16 bits. Is this because of a compiler
warning? If the use of 0xffff is not obvious, why would 0xfffe be any
better.

> >>  /* Device present registers. */
> >>  #define MDIO_DEVS_PRESENT(devad)	(1 << (devad))
> >> +#define MDIO_DEVS_C22PRESENT		MDIO_DEVS_PRESENT(0)
> > 
> > Err. The commit message says you did not add this...
> > 
> Maybe I'm not clear enough in the commit message. Typically we have two
> constants for a device:
> 
> MDIO_MMD_XXX (for the device)
> MDIO_DEVS_XXX (for the bit of the device in the device list bitmap)
> 
> For the C22PRESENT flag I don't define the first one (because it's
> not a device) but the second one (because it uses a bit in the device
> list bitmap).

This would be better as a separate patch. It is not used here, and the
explanation can then be made clearer.

	    Andrew