Re: [PATCH v2 3/3] net: phy: add Rust Asix PHY driver

From: FUJITA Tomonori <fujita.tomonori@gmail.com>
To: gregkh@linuxfoundation.org
Cc: fujita.tomonori@gmail.com, netdev@vger.kernel.org,
	rust-for-linux@vger.kernel.org, andrew@lunn.ch,
	miguel.ojeda.sandonis@gmail.com
Subject: Re: [PATCH v2 3/3] net: phy: add Rust Asix PHY driver
Date: Fri, 06 Oct 2023 23:30:54 +0900 (JST)	[thread overview]
Message-ID: <20231006.233054.318856023136859648.fujita.tomonori@gmail.com> (raw)
In-Reply-To: <2023100637-episode-espresso-7a5a@gregkh>

On Fri, 6 Oct 2023 16:12:24 +0200
Greg KH <gregkh@linuxfoundation.org> wrote:

> On Fri, Oct 06, 2023 at 10:53:25PM +0900, FUJITA Tomonori wrote:
>> On Fri, 6 Oct 2023 12:31:59 +0200
>> Greg KH <gregkh@linuxfoundation.org> wrote:
>> 
>> > On Fri, Oct 06, 2023 at 06:49:11PM +0900, FUJITA Tomonori wrote:
>> >> +config AX88796B_RUST_PHY
>> >> +	bool "Rust reference driver"
>> >> +	depends on RUST && AX88796B_PHY
>> >> +	default n
>> > 
>> > Nit, "n" is always the default, there is no need for this line.
>> 
>> Understood, I'll remove this line.
>> 
>> >> +	help
>> >> +	  Uses the Rust version driver for Asix PHYs.
>> > 
>> > You need more text here please.  Provide a better description of what
>> > hardware is supported and the name of the module if it is built aas a
>> > module.
>> > 
>> > Also that if you select this one, the C driver will not be built (which
>> > is not expressed in the Kconfig language, why not?
>> 
>> Because the way to load a PHY driver module can't handle multiple
>> modules with the same phy id (a NIC driver loads a PHY driver module).
>> There is no machinism to specify which PHY driver module should be
>> loaded when multiple PHY modules have the same phy id (as far as I know).
> 
> Sorry, I know that, I mean I am pretty sure you can express this "one or
> the other" type of restriction in Kconfig, no need to encode it in the
> Makefile logic.
> 
> Try doing "depens on AX88796B_PHY=n" as the dependency for the rust
> driver.

You meant the following?

config AX88796B_PHY
	tristate "Asix PHYs"
	help
	  Currently supports the Asix Electronics PHY found in the X-Surf 100
	  AX88796B package.

config AX88796B_RUST_PHY
	bool "Rust reference driver"
	depends on RUST && AX88796B_PHY
	default n
	help
	  Uses the Rust version driver for Asix PHYs.

The problem is that there are NIC drivers that `select
AX88796B_PHY`. the Kconfig language doesn't support something like
`select AX88796B_PHY or AX88796B_RUST_PHY`, I guess.