Message-ID: <20231102155521.2yo5qpugdhkjy22x@skbuf>
Date: Thu, 2 Nov 2023 17:55:21 +0200
From: Vladimir Oltean <olteanv@...il.com>
To: Linus Walleij <linus.walleij@...aro.org>
Cc: Luiz Angelo Daros de Luca <luizluca@...il.com>, netdev@...r.kernel.org,
	alsi@...g-olufsen.dk, andrew@...n.ch, vivien.didelot@...il.com,
	f.fainelli@...il.com, davem@...emloft.net, kuba@...nel.org,
	pabeni@...hat.com, robh+dt@...nel.org, krzk+dt@...nel.org,
	arinc.unal@...nc9.com
Subject: Re: [PATCH net-next v2 3/3] net: dsa: realtek: support reset
 controller

On Thu, Nov 02, 2023 at 03:59:48PM +0100, Linus Walleij wrote:
> I don't know if this is an answer to your question, but look at what I did in
> 
> drivers/usb/fotg210/Makefile:
> 
> # This setup links the different object files into one single
> # module so we don't have to EXPORT() a lot of internal symbols
> # or create unnecessary submodules.
> fotg210-objs-y                          += fotg210-core.o
> fotg210-objs-$(CONFIG_USB_FOTG210_HCD)  += fotg210-hcd.o
> fotg210-objs-$(CONFIG_USB_FOTG210_UDC)  += fotg210-udc.o
> fotg210-objs                            := $(fotg210-objs-y)
> obj-$(CONFIG_USB_FOTG210)               += fotg210.o
> 
> Everything starting with CONFIG_* is a Kconfig option obviously.
> 
> The final module is just one file named fotg210.ko no matter whether
> HCD (host controller), UDC (device controller) or both parts were
> compiled into it. Often you just need one of them, sometimes you may
> need both.
> 
> It's a pretty clean example of how you do this "one module from
> several optional parts" using Kbuild.

To be clear, something like this is what you mean, right?

diff --git a/drivers/net/dsa/realtek/Kconfig b/drivers/net/dsa/realtek/Kconfig
index 060165a85fb7..857a039fb0f1 100644
--- a/drivers/net/dsa/realtek/Kconfig
+++ b/drivers/net/dsa/realtek/Kconfig
@@ -15,39 +15,37 @@ menuconfig NET_DSA_REALTEK
 
 if NET_DSA_REALTEK
 
+config NET_DSA_REALTEK_INTERFACE
+	tristate
+	help
+	  Common interface driver for accessing Realtek switches, either
+	  through MDIO or SMI.
+
 config NET_DSA_REALTEK_MDIO
-	tristate "Realtek MDIO interface driver"
-	depends on OF
-	depends on NET_DSA_REALTEK_RTL8365MB || NET_DSA_REALTEK_RTL8366RB
-	depends on NET_DSA_REALTEK_RTL8365MB || !NET_DSA_REALTEK_RTL8365MB
-	depends on NET_DSA_REALTEK_RTL8366RB || !NET_DSA_REALTEK_RTL8366RB
+	tristate "Realtek MDIO interface support"
 	help
 	  Select to enable support for registering switches configured
 	  through MDIO.
 
 config NET_DSA_REALTEK_SMI
-	tristate "Realtek SMI interface driver"
-	depends on OF
-	depends on NET_DSA_REALTEK_RTL8365MB || NET_DSA_REALTEK_RTL8366RB
-	depends on NET_DSA_REALTEK_RTL8365MB || !NET_DSA_REALTEK_RTL8365MB
-	depends on NET_DSA_REALTEK_RTL8366RB || !NET_DSA_REALTEK_RTL8366RB
+	bool "Realtek SMI interface support"
 	help
 	  Select to enable support for registering switches connected
 	  through SMI.
 
 config NET_DSA_REALTEK_RTL8365MB
 	tristate "Realtek RTL8365MB switch subdriver"
-	imply NET_DSA_REALTEK_SMI
-	imply NET_DSA_REALTEK_MDIO
+	select NET_DSA_REALTEK_INTERFACE
 	select NET_DSA_TAG_RTL8_4
+	depends on OF
 	help
 	  Select to enable support for Realtek RTL8365MB-VC and RTL8367S.
 
 config NET_DSA_REALTEK_RTL8366RB
 	tristate "Realtek RTL8366RB switch subdriver"
-	imply NET_DSA_REALTEK_SMI
-	imply NET_DSA_REALTEK_MDIO
+	select NET_DSA_REALTEK_INTERFACE
 	select NET_DSA_TAG_RTL4_A
+	depends on OF
 	help
 	  Select to enable support for Realtek RTL8366RB.
 
diff --git a/drivers/net/dsa/realtek/Makefile b/drivers/net/dsa/realtek/Makefile
index 0aab57252a7c..35b7734c0ad0 100644
--- a/drivers/net/dsa/realtek/Makefile
+++ b/drivers/net/dsa/realtek/Makefile
@@ -1,6 +1,15 @@
 # SPDX-License-Identifier: GPL-2.0
-obj-$(CONFIG_NET_DSA_REALTEK_MDIO) 	+= realtek-mdio.o
-obj-$(CONFIG_NET_DSA_REALTEK_SMI) 	+= realtek-smi.o
+
+obj-$(CONFIG_NET_DSA_REALTEK_INTERFACE) := realtek-interface.o
+
+realtek-interface-objs			:= realtek-interface-common.o
+ifdef CONFIG_NET_DSA_REALTEK_MDIO
+realtek-interface-objs			+= realtek-mdio.o
+endif
+ifdef CONFIG_NET_DSA_REALTEK_SMI
+realtek-interface-objs			+= realtek-smi.o
+endif
+
 obj-$(CONFIG_NET_DSA_REALTEK_RTL8366RB) += rtl8366.o
 rtl8366-objs 				:= rtl8366-core.o rtl8366rb.o
 obj-$(CONFIG_NET_DSA_REALTEK_RTL8365MB) += rtl8365mb.o
diff --git a/drivers/net/dsa/realtek/realtek-interface-common.c b/drivers/net/dsa/realtek/realtek-interface-common.c
new file mode 100644
index 000000000000..bb7c77cdb9e2
--- /dev/null
+++ b/drivers/net/dsa/realtek/realtek-interface-common.c
@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+#include <linux/module.h>
+
+#include "realtek-mdio.h"
+#include "realtek-smi.h"
+
+static int __init realtek_interface_init(void)
+{
+	int err;
+
+	err = realtek_mdio_init();
+	if (err)
+		return err;
+
+	err = realtek_smi_init();
+	if (err) {
+		realtek_smi_exit();
+		return err;
+	}
+
+	return 0;
+}
+module_init(realtek_interface_init);
+
+static void __exit realtek_interface_exit(void)
+{
+	realtek_smi_exit();
+	realtek_mdio_exit();
+}
+module_exit(realtek_interface_exit);
+
+MODULE_AUTHOR("Luiz Angelo Daros de Luca <luizluca@...il.com>");
+MODULE_AUTHOR("Linus Walleij <linus.walleij@...aro.org>");
+MODULE_DESCRIPTION("Driver for interfacing with Realtek switches via MDIO or SMI");
+MODULE_LICENSE("GPL");
diff --git a/drivers/net/dsa/realtek/realtek-mdio.c b/drivers/net/dsa/realtek/realtek-mdio.c
index 292e6d087e8b..6997dec14de2 100644
--- a/drivers/net/dsa/realtek/realtek-mdio.c
+++ b/drivers/net/dsa/realtek/realtek-mdio.c
@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0+
-/* Realtek MDIO interface driver
+/* Realtek MDIO interface support
  *
  * ASICs we intend to support with this driver:
  *
@@ -19,12 +19,12 @@
  * Copyright (C) 2009-2010 Gabor Juhos <juhosg@...nwrt.org>
  */
 
-#include <linux/module.h>
 #include <linux/of.h>
 #include <linux/overflow.h>
 #include <linux/regmap.h>
 
 #include "realtek.h"
+#include "realtek-mdio.h"
 
 /* Read/write via mdiobus */
 #define REALTEK_MDIO_CTRL0_REG		31
@@ -283,8 +283,12 @@ static struct mdio_driver realtek_mdio_driver = {
 	.shutdown = realtek_mdio_shutdown,
 };
 
-mdio_module_driver(realtek_mdio_driver);
+int realtek_mdio_init(void)
+{
+	return mdio_driver_register(&realtek_mdio_driver);
+}
 
-MODULE_AUTHOR("Luiz Angelo Daros de Luca <luizluca@...il.com>");
-MODULE_DESCRIPTION("Driver for Realtek ethernet switch connected via MDIO interface");
-MODULE_LICENSE("GPL");
+void realtek_mdio_exit(void)
+{
+	mdio_driver_unregister(&realtek_mdio_driver);
+}
diff --git a/drivers/net/dsa/realtek/realtek-mdio.h b/drivers/net/dsa/realtek/realtek-mdio.h
new file mode 100644
index 000000000000..941b4ef9d531
--- /dev/null
+++ b/drivers/net/dsa/realtek/realtek-mdio.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+
+#ifndef _REALTEK_MDIO_H
+#define _REALTEK_MDIO_H
+
+#if IS_ENABLED(CONFIG_NET_DSA_REALTEK_MDIO)
+
+int realtek_mdio_init(void);
+void realtek_mdio_exit(void);
+
+#else
+
+static inline int realtek_mdio_init(void)
+{
+	return 0;
+}
+
+static inline void realtek_mdio_exit(void)
+{
+}
+
+#endif
+
+#endif
diff --git a/drivers/net/dsa/realtek/realtek-smi.c b/drivers/net/dsa/realtek/realtek-smi.c
index 755546ed8db6..4c282bfc884d 100644
--- a/drivers/net/dsa/realtek/realtek-smi.c
+++ b/drivers/net/dsa/realtek/realtek-smi.c
@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0+
-/* Realtek Simple Management Interface (SMI) driver
+/* Realtek Simple Management Interface (SMI) interface
  * It can be discussed how "simple" this interface is.
  *
  * The SMI protocol piggy-backs the MDIO MDC and MDIO signals levels
@@ -26,7 +26,6 @@
  */
 
 #include <linux/kernel.h>
-#include <linux/module.h>
 #include <linux/device.h>
 #include <linux/spinlock.h>
 #include <linux/skbuff.h>
@@ -40,6 +39,7 @@
 #include <linux/if_bridge.h>
 
 #include "realtek.h"
+#include "realtek-smi.h"
 
 #define REALTEK_SMI_ACK_RETRY_COUNT		5
 
@@ -560,8 +560,13 @@ static struct platform_driver realtek_smi_driver = {
 	.remove_new = realtek_smi_remove,
 	.shutdown = realtek_smi_shutdown,
 };
-module_platform_driver(realtek_smi_driver);
 
-MODULE_AUTHOR("Linus Walleij <linus.walleij@...aro.org>");
-MODULE_DESCRIPTION("Driver for Realtek ethernet switch connected via SMI interface");
-MODULE_LICENSE("GPL");
+int realtek_smi_init(void)
+{
+	return platform_driver_register(&realtek_smi_driver);
+}
+
+void realtek_smi_exit(void)
+{
+	platform_driver_unregister(&realtek_smi_driver);
+}
diff --git a/drivers/net/dsa/realtek/realtek-smi.h b/drivers/net/dsa/realtek/realtek-smi.h
new file mode 100644
index 000000000000..9a4838321f94
--- /dev/null
+++ b/drivers/net/dsa/realtek/realtek-smi.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+
+#ifndef _REALTEK_SMI_H
+#define _REALTEK_SMI_H
+
+#if IS_ENABLED(CONFIG_NET_DSA_REALTEK_SMI)
+
+int realtek_smi_init(void);
+void realtek_smi_exit(void);
+
+#else
+
+static inline int realtek_smi_init(void)
+{
+	return 0;
+}
+
+static inline void realtek_smi_exit(void)
+{
+}
+
+#endif
+
+#endif
-- 
2.34.1


It looks pretty reasonable to me. More stuff could go into
realtek-interface-common.c, that could be called directly from
realtek-smi.c and realtek-mdio.c without exporting anything.

I've eliminated the possibility for the SMI and MDIO options to be
anything other than y or n, because only a single interface module
(the common one) exists, and the y/n/m quality of that is
implied/selected by the drivers which depend on it. I hope I wasn't too
trigger-happy with this.

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