linux-kernel - Re: [net-next RFC PATCH 0/3] net: phy: detach PHY driver OPs from phy

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Date: Sun, 18 Feb 2024 00:22:45 +0100
From: Christian Marangi <ansuelsmth@...il.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Michael Hennerich <michael.hennerich@...log.com>,
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Subject: Re: [net-next RFC PATCH 0/3] net: phy: detach PHY driver OPs from
 phy_driver struct

On Sat, Feb 17, 2024 at 07:53:08PM +0000, Russell King (Oracle) wrote:
> On Sat, Feb 17, 2024 at 08:41:11PM +0100, Christian Marangi wrote:
> > Posting as RFC due to the massive change to a fundamental struct.
> > 
> > While adding some PHY ID for Aquantia, I notice that there is a
> > big problem with duplicating OPs with each PHY.
> > 
> > The original idea to prevent this was to use mask on the PHY ID
> > and identify PHY Family. Problem is that OEM started to use all
> > kind of PHY ID and this is not doable, hence for PHY that have
> > the same OPs, we have to duplicate all of them.
> > 
> > This is present in Aquantia PHY, but is much more present in
> > other PHY, especially in the BCM7XXX where they use a big macro
> > for common PHYs.
> > 
> > To reduce patch delta, I added the additional variable without
> > adding tabs as this would have resulted in a massive patch.
> > Also to have patch bisectable, this change has to be in one go
> > hence I had to use this trick to reduce patch delta.
> > 
> > Other solution to this problem were to introduce additional
> > variables to phy_driver struct but that would have resulted
> > in having 2 different way to do the same thing and that is not O.K.
> > 
> > I took care to compile-test all the PHY, only exception is the unique
> > RUST driver, where I still have to learn that funny language and
> > I didn't had time to update it, so that is the only driver that
> > I think require some fixup.
> > 
> > I posted 2 example that would benefits from this change, but I can
> > find much more in other PHY driver.
> 
> Would it make more sense instead of this big churn, to instead
> introduce into struct phy_driver:
> 
> 	struct mdio_device_id	*ids;
> 
> which would then allow a phy_driver structure to be matched by
> several device IDs?

Yes that was an alternative idea, but is it good to then have 2 way to
declare PHY ID?

Also the name should be changed... Maybe an array of a struct PHY_ID,
name that ends with a sentinel?

> 
> We then would not need to touch any of the existing drivers initially,
> and a later cleanup could be to identify those where all the ops are
> the same for several phy_driver structures, and convert them over.

We have many PHY that already have macro to define the same OPs and
change only name PHY ID and mask.

-- 
	Ansuel