netdev - Re: [PATCH 0/1] add MDIO bus multiplexer driven by a regmap device

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Date:   Wed, 30 Jan 2019 16:22:43 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Pankaj Bansal <pankaj.bansal@....com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Varun Sethi <V.Sethi@....com>
Subject: Re: [PATCH 0/1] add MDIO bus multiplexer driven by a regmap device

On Wed, Jan 30, 2019 at 11:21:57AM +0000, Pankaj Bansal wrote:
> Add support for an MDIO bus multiplexer controlled by a regmap device, like an 
> FPGA.
> 
> These apis is an extension of the existing driver 
> drivers/net/phy/mdio-mux-mmioreg.c.
> 
> The problem with mmioreg driver is that it can operate only on memory mapped 
> devices.
> but if we have a device that controls mdio muxing and that device is controlled 
> using
> i2c or spi, then it will not work.
> 
> Therefore, added apis that can be used by regmap device to control mdio mux.
> 
> Tested on a NXP LX2160AQDS board which uses the "QIXIS" FPGA attached to the 
> i2c bus.
> 
> This is my second attempt at this.
> In my previous approach i wrote a separate driver for regmap apis. But then i
> realized that it is not meant to control a specific device.
> It is meant to control some registers of parent device. Therefore, IMO this 
> should not be a
> Platform driver and there should not be any "compatible" property to which this 
> driver is associated.

Hi Pankaj

It is not clear to me how you actually use this. You also need to
document the device tree binding. It could be when you write that
documentation it then becomes clear how it should be used.

Do you have patches adding support for this to the LX2160AQDS?  Seeing
that would also help.

Thanks
	Andrew