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

[FUJITA Tomonori <fujita.tomonori@gmail.com>]

On Sun, 24 Sep 2023 12:10:58 +0200
Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> wrote:

> On Sun, Sep 24, 2023 at 11:38 AM FUJITA Tomonori
> <fujita.tomonori@gmail.com> wrote:
>>
>> With that approach, you can enable both C and Rust versions? It might
>> breaks auto-module-loading.
> 
> No, I meant that it would still be one or the other, i.e. `N` would
> mean "use the normal, existing, production C one"; while `Y` would
> replace it with the Rust reference driver.

I see.

>> If a module selects CONFIG_AX88796B_PHY, then we need
>> CONFIG_AX88796B_C_PHY or CONFIG_AX88796B_RUST_PHY.
> 
> Are you talking about the inner one perhaps? What I meant is that
> `obj-$(CONFIG_AX88796B_PHY)` expands to `obj-` if
> `CONFIG_AX88796B_PHY` is not defined, so it already does the job of
> the outer `ifdef`, right?

Ah, would work, I guess.

Something simpler like the following might work.

diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
index 107880d13d21..e4d941f0ebe4 100644
--- a/drivers/net/phy/Kconfig
+++ b/drivers/net/phy/Kconfig
@@ -107,6 +107,13 @@ config AX88796B_PHY
 	  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.
+
 config BROADCOM_PHY
 	tristate "Broadcom 54XX PHYs"
 	select BCM_NET_PHYLIB
diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile
index c945ed9bd14b..58d7dfb095ab 100644
--- a/drivers/net/phy/Makefile
+++ b/drivers/net/phy/Makefile
@@ -41,7 +41,11 @@ aquantia-objs			+= aquantia_hwmon.o
 endif
 obj-$(CONFIG_AQUANTIA_PHY)	+= aquantia.o
 obj-$(CONFIG_AT803X_PHY)	+= at803x.o
-obj-$(CONFIG_AX88796B_PHY)	+= ax88796b.o
+ifdef CONFIG_AX88796B_RUST_PHY
+  obj-$(CONFIG_AX88796B_PHY)	+= ax88796b_rust.o
+else
+  obj-$(CONFIG_AX88796B_PHY)	+= ax88796b.o
+endif
 obj-$(CONFIG_BCM54140_PHY)	+= bcm54140.o
 obj-$(CONFIG_BCM63XX_PHY)	+= bcm63xx.o
 obj-$(CONFIG_BCM7XXX_PHY)	+= bcm7xxx.o