netdev - Re: [PATCH net-next] net: phy: Allow building mdio-boardinfo into the kernel

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Date:   Wed, 29 Mar 2017 10:09:46 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Networking <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Andrew Lunn <andrew@...n.ch>, rmk+kernel@...linux.org.uk
Subject: Re: [PATCH net-next] net: phy: Allow building mdio-boardinfo into the kernel

On Tue, Mar 28, 2017 at 9:57 PM, Florian Fainelli <f.fainelli@...il.com> wrote:
> mdio-boardinfo contains code that is helpful for platforms to register
> specific MDIO bus devices independent of how CONFIG_MDIO_DEVICE or
> CONFIG_PHYLIB will be selected (modular or built-in). In order to make
> that possible, let's do the following:
>
> - descend into drivers/net/phy/ unconditionally
>
> - make mdiobus_setup_mdiodev_from_board_info() take a callback argument
>   which allows us not to expose the internal MDIO board info list and
>   mutex, yet maintain the logic within the same file
>
> - relocate the code that creates a MDIO device into
>   drivers/net/phy/mdio_bus.c
>
> - build mdio-boardinfo.o into the kernel as soon as MDIO_DEVICE is
>   defined (y or m)
>
> Fixes: 90eff9096c01 ("net: phy: Allow splitting MDIO bus/device support from PHYs")
> Fixes: 648ea0134069 ("net: phy: Allow pre-declaration of MDIO devices")
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>

It survived the overnight randconfig build,

Tested-by: Arnd Bergmann <arnd@...db.de>

On a related note, I ran into one more case of a network driver selecting a
particular PHY:

drivers/net/built-in.o: In function `octeon_mdiobus_remove':
wilink_platform_data.c:(.text+0xe58): undefined reference to
`mdiobus_unregister'
wilink_platform_data.c:(.text+0xe60): undefined reference to `mdiobus_free'
drivers/net/built-in.o: In function `octeon_mdiobus_probe':
wilink_platform_data.c:(.text+0xec8): undefined reference to
`devm_mdiobus_alloc_size'
wilink_platform_data.c:(.text+0x1090): undefined reference to
`of_mdiobus_register'
wilink_platform_data.c:(.text+0x10d0): undefined reference to `mdiobus_free'

Building with this hack fixes the three instances I found so far, but my
current workaround seems rather fragile:

@@ -28,7 +28,7 @@ config MDIO_BCM_UNIMAC

 config MDIO_BITBANG
        tristate "Bitbanged MDIO buses"
-       depends on !(MDIO_DEVICE=y && PHYLIB=m)
+       depends on m || !(MDIO_DEVICE=y && PHYLIB=m)
        help
          This module implements the MDIO bus protocol in software,
          for use by low level drivers that export the ability to
@@ -118,6 +118,7 @@ config MDIO_OCTEON
 config MDIO_SUN4I
        tristate "Allwinner sun4i MDIO interface support"
        depends on ARCH_SUNXI
+       depends on m || !(MDIO_DEVICE=y && PHYLIB=m)
        help
          This driver supports the MDIO interface found in the network
          interface units of the Allwinner SoC that have an EMAC (A10,
@@ -109,6 +109,7 @@ config MDIO_OCTEON
        tristate "Octeon and some ThunderX SOCs MDIO buses"
        depends on 64BIT
        depends on HAS_IOMEM
+       depends on m || !(MDIO_DEVICE=y && PHYLIB=m)
        select MDIO_CAVIUM
        help
          This module provides a driver for the Octeon and ThunderX MDIO

The configuration causing it is something like this:

CONFIG_MDIO_OCTEON=y
CONFIG_MDIO_DEVICE=y
CONFIG_PHYLIB=m

This is what I'm trying now:

--- a/drivers/net/phy/Kconfig
+++ b/drivers/net/phy/Kconfig
@@ -7,7 +7,16 @@ menuconfig MDIO_DEVICE
        help
           MDIO devices and driver infrastructure code.

-if MDIO_DEVICE
+config MDIO_BUS
+       tristate
+       default m if PHYLIB=m
+       default MDIO_DEVICE
+       help
+         This internal symbol is used for link time dependencies and it
+         reflects whether the mdio_bus/mdio_device code is built as a
+         loadable module or built-in.
+
+if MDIO_BUS

 config MDIO_BCM_IPROC
        tristate "Broadcom iProc MDIO bus controller"
@@ -28,7 +37,6 @@ config MDIO_BCM_UNIMAC

 config MDIO_BITBANG
        tristate "Bitbanged MDIO buses"
-       depends on m || !(MDIO_DEVICE=y && PHYLIB=m)
        help
          This module implements the MDIO bus protocol in software,
          for use by low level drivers that export the ability to
@@ -109,7 +117,6 @@ config MDIO_OCTEON
        tristate "Octeon and some ThunderX SOCs MDIO buses"
        depends on 64BIT
        depends on HAS_IOMEM
-       depends on m || !(MDIO_DEVICE=y && PHYLIB=m)
        select MDIO_CAVIUM
        help
          This module provides a driver for the Octeon and ThunderX MDIO
@@ -119,7 +126,6 @@ config MDIO_OCTEON
 config MDIO_SUN4I
        tristate "Allwinner sun4i MDIO interface support"
        depends on ARCH_SUNXI
-       depends on m || !(MDIO_DEVICE=y && PHYLIB=m)
        help
          This driver supports the MDIO interface found in the network
          interface units of the Allwinner SoC that have an EMAC (A10,


    Arnd