netdev - Re: [PATCH v3 7/9] net: mvmdio: add xmdio xsmi support

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Message-ID: <20170612101739.GA4902@n2100.armlinux.org.uk>
Date:   Mon, 12 Jun 2017 11:17:39 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Antoine Tenart <antoine.tenart@...e-electrons.com>
Cc:     davem@...emloft.net, jason@...edaemon.net, andrew@...n.ch,
        gregory.clement@...e-electrons.com,
        sebastian.hesselbarth@...il.com, f.fainelli@...il.com,
        thomas.petazzoni@...e-electrons.com, nadavh@...vell.com,
        mw@...ihalf.com, netdev@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 7/9] net: mvmdio: add xmdio xsmi support

On Mon, Jun 12, 2017 at 11:57:43AM +0200, Antoine Tenart wrote:
> +static const struct orion_mdio_ops *orion_mdio_get_ops(struct orion_mdio_dev *dev,
> +						       int regnum)
> +{
> +	if (dev->bus_type == BUS_TYPE_XSMI && (regnum & MII_ADDR_C45))
> +		return &orion_mdio_xsmi_ops;
> +	else if (dev->bus_type == BUS_TYPE_SMI)
> +		return &orion_mdio_smi_ops;
> +
> +	return ERR_PTR(-EOPNOTSUPP);
> +}

Oh, this is where you're doing it - I'm not sure having this complexity
is really necessary - there is no dynamic choice between the two.  This
seems to be way over-engineered.

You might as well make the SMI operations fail if MII_ADDR_C45 is set,
and the XSMI operations fail if MII_ADDR_C45 is not set.

Hmm, I think this whole driver is over-engineered:

1. the mdio read/write functions implement their own locking.

   At the MDIO level, there is already locking in the form of a per-bus
   lock "bus->mdio_lock" which will be taken whenever either of these
   functions is called.  So the driver's "dev->lock" is redundant.

2. with the redundant locking removed, orion_mdio_write() becomes a
   call to orion_mdio_wait_ready() followed by a call to dev->ops->write.
   It seems that orion_mdio_wait_ready() could be a library function
   shared between a SMI version of orion_mdio_write() and a XSMI version.

3. the same is really true of orion_mdio_read(), although that function
   is a little more complex in itself, the result would actually end up
   being simpler.

With those changes together, it elimates "struct orion_mdio_ops" entirely,
and I think makes the driver smaller, simpler, and cleaner.

-- 
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