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

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Date:   Fri, 8 Feb 2019 19:16:52 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
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

On 08.02.2019 15:02, Andrew Lunn wrote:
> On Fri, Feb 08, 2019 at 08:12:47AM +0100, Heiner Kallweit wrote:
>> Bit 0 in register 1.5 doesn't represent a device but is a flag that
>> Clause 22 registers are present. Therefore disregard this bit when
>> populating the device list. If code needs this information it
>> should read register 1.5 directly instead of accessing the device
>> list. Because this bit doesn't represent a device I didn't add a
>> MDIO_MMD_C22PRESENT constant or similar.
>>
>> Signed-off-by: Heiner Kallweit <hkallweit1@...il.com>
>> ---
>>  drivers/net/phy/phy_device.c | 3 ++-
>>  include/uapi/linux/mdio.h    | 1 +
>>  2 files changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
>> index 9369e1323..c2316a117 100644
>> --- a/drivers/net/phy/phy_device.c
>> +++ b/drivers/net/phy/phy_device.c
>> @@ -682,7 +682,8 @@ static int get_phy_c45_devs_in_pkg(struct mii_bus *bus, int addr, int dev_addr,
>>  	phy_reg = mdiobus_read(bus, addr, reg_addr);
>>  	if (phy_reg < 0)
>>  		return -EIO;
>> -	*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?
But sure, I can make it more explicit.

>>  
>>  	return 0;
>>  }
>> diff --git a/include/uapi/linux/mdio.h b/include/uapi/linux/mdio.h
>> index 2e6e309f0..0e012b168 100644
>> --- a/include/uapi/linux/mdio.h
>> +++ b/include/uapi/linux/mdio.h
>> @@ -115,6 +115,7 @@
>>  
>>  /* 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).

>      Andrew
> 
Heiner