linux-kernel - Re: [PATCH] usb: Kconfig: make USB_ULPI_BUS select USB

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Date:   Tue, 13 Sep 2016 09:04:08 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Peter Chen <hzpeterchen@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Chen <peter.chen@....com>,
        Felipe Balbi <balbi@...nel.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: Kconfig: make USB_ULPI_BUS select USB_COMMON

On Tuesday, September 13, 2016 9:48:55 AM CEST Peter Chen wrote:
> On Mon, Sep 12, 2016 at 05:36:23PM +0200, Arnd Bergmann wrote:
> > Moving the CONFIG_USB_ULPI_BUS option to the top-level Kconfig file
> > means that we can enable it without any of the other USB support,
> > leading to a build error because Kbuild never enters the
> > drivers/usb/common/ directory without CONFIG_USB_COMMON:
> > 
> > ERROR: "ulpi_unregister_driver" [drivers/phy/phy-tusb1210.ko] undefined!
> > ERROR: "__ulpi_register_driver" [drivers/phy/phy-tusb1210.ko] undefined!
> > ERROR: "ulpi_write" [drivers/phy/phy-tusb1210.ko] undefined!
> > 
> 
> Thanks, Arnd. I have submitted the fix.
> 
> https://git.kernel.org/cgit/linux/kernel/git/gregkh/usb.git/commit/?h=usb-next&id=6406c3d226374c28d452b11db3b5ac241ce26191

I see you used 'depends on USB_COMMON' though instead of 'select USB_COMMON'.

This seems inconsistent with how we handle the other places after the patch
I did earlier this year [see below].

It probably works fine for now, but having a mix of 'depends on' and 'select'
can be confusing for users as well as create dependency loops that break
the build.

	Arnd

commit badf6d47f8a93098c6e05fdeb735b44b61877451
Author: Arnd Bergmann <arnd@...db.de>
Date:   Wed Mar 23 17:45:08 2016 +0100

    usb: common: rework CONFIG_USB_COMMON logic
    
    The phy-am335x driver selects 'USB_COMMON', but all other drivers
    use 'depends on' for that symbol, and it depends on USB || USB_GADGET
    itself, which causes a Kconfig warning:
    
    warning: (AM335X_PHY_USB) selects USB_COMMON which has unmet direct dependencies (USB_SUPPORT && (USB || USB_GADGET))
    
    As suggested by Felipe Balbi, this turns the logic around, and makes
    'USB_COMMON' selected by everything else that needs it, so we can
    remove the dependencies.
    
    Fixes: 59f042f644c5 ("usb: phy: phy-am335x: bypass first VBUS sensing for host-only mode")
    Signed-off-by: Arnd Bergmann <arnd@...db.de>
    Acked-by: Felipe Balbi <balbi@...nel.org>
    Reviewed-by: Peter Chen <peter.chen@....com>
    Signed-off-by: Felipe Balbi <felipe.balbi@...ux.intel.com>

diff --git a/drivers/phy/Kconfig b/drivers/phy/Kconfig
index 26566db09de0..e92b97cd6056 100644
--- a/drivers/phy/Kconfig
+++ b/drivers/phy/Kconfig
@@ -250,7 +250,8 @@ config PHY_SUN9I_USB
 	tristate "Allwinner sun9i SoC USB PHY driver"
 	depends on ARCH_SUNXI && HAS_IOMEM && OF
 	depends on RESET_CONTROLLER
-	depends on USB_COMMON
+	depends on USB_SUPPORT
+	select USB_COMMON
 	select GENERIC_PHY
 	help
 	  Enable this to support the transceiver that is part of Allwinner
diff --git a/drivers/usb/Kconfig b/drivers/usb/Kconfig
index 8ed451dd651e..8689dcba5201 100644
--- a/drivers/usb/Kconfig
+++ b/drivers/usb/Kconfig
@@ -31,8 +31,6 @@ if USB_SUPPORT
 
 config USB_COMMON
 	tristate
-	default y
-	depends on USB || USB_GADGET
 
 config USB_ARCH_HAS_HCD
 	def_bool y
@@ -41,6 +39,7 @@ config USB_ARCH_HAS_HCD
 config USB
 	tristate "Support for Host-side USB"
 	depends on USB_ARCH_HAS_HCD
+	select USB_COMMON
 	select NLS  # for UTF-8 strings
 	---help---
 	  Universal Serial Bus (USB) is a specification for a serial bus
diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig
index af5d922a8f5d..2057add439f0 100644
--- a/drivers/usb/gadget/Kconfig
+++ b/drivers/usb/gadget/Kconfig
@@ -15,6 +15,7 @@
 
 menuconfig USB_GADGET
 	tristate "USB Gadget Support"
+	select USB_COMMON
 	select NLS
 	help
 	   USB is a master/slave protocol, organized with one master