Re: [PATCH v17 7/7] usb: Specify dependencies on USB_XHCI_PLATFORM with 'depends on'

From: Alan Stern <stern@rowland.harvard.edu>
To: Matthias Kaehlcke <mka@chromium.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Rob Herring <robh+dt@kernel.org>,
	Frank Rowand <frowand.list@gmail.com>,
	Mathias Nyman <mathias.nyman@intel.com>,
	Felipe Balbi <balbi@kernel.org>,
	linux-kernel@vger.kernel.org,
	Krzysztof Kozlowski <krzk@kernel.org>,
	Stephen Boyd <swboyd@chromium.org>,
	Peter Chen <peter.chen@kernel.org>,
	linux-usb@vger.kernel.org, devicetree@vger.kernel.org,
	Douglas Anderson <dianders@chromium.org>,
	Roger Quadros <rogerq@kernel.org>,
	Michal Simek <michal.simek@xilinx.com>,
	Ravi Chandra Sadineni <ravisadineni@chromium.org>,
	Bastien Nocera <hadess@hadess.net>, Andrew Lunn <andrew@lunn.ch>,
	Aswath Govindraju <a-govindraju@ti.com>,
	Dmitry Osipenko <digetx@gmail.com>,
	Gregory Clement <gregory.clement@bootlin.com>,
	Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
	Lukas Bulwahn <lukas.bulwahn@gmail.com>,
	Pawel Laszczak <pawell@cadence.com>,
	Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>,
	Tony Lindgren <tony@atomide.com>,
	linux-arm-kernel@lists.infradead.org, linux-omap@vger.kernel.org,
	linux-samsung-soc@vger.kernel.org
Subject: Re: [PATCH v17 7/7] usb: Specify dependencies on USB_XHCI_PLATFORM with 'depends on'
Date: Tue, 16 Nov 2021 21:21:44 -0500	[thread overview]
Message-ID: <20211117022144.GA158646@rowland.harvard.edu> (raw)
In-Reply-To: <20211116120642.v17.7.If248f05613bbb06a44eb0b0909be5d97218f417b@changeid>

On Tue, Nov 16, 2021 at 12:07:39PM -0800, Matthias Kaehlcke wrote:
> Some USB controller drivers that depend on the xhci-plat driver
> specify this dependency using 'select' in Kconfig. This is not
> recommended for symbols that have other dependencies as it may
> lead to invalid configurations. Use 'depends on' to specify the
> dependency instead of 'select'.
> 
> For dwc3 specify the dependency on USB_XHCI_PLATFORM in
> USB_DWC3_HOST and USB_DWC3_DUAL_ROLE. Also adjust the
> dependencies of USB_DWC3_CORE to make sure that at least one
> of USB_DWC3_HOST, USB_DWC3_GADGET or USB_DWC3_DUAL_ROLE can be
> selected.
> 
> Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
> Reviewed-by: Roger Quadros <rogerq@kernel.org>
> Reviewed-by: Douglas Anderson <dianders@chromium.org>
> ---
> 
> Changes in v17:
> - removed explicit dependency on USB from USB_DWC3
> - added 'Reviewed-by' tags from Roger and Doug
> 
> Changes in v16:
> - none
> 
> Changes in v15:
> - adjusted dependencies of USB_DWC3_CORE to make sure it can only
>   be enabled when at least one of USB_DWC3_HOST, USB_DWC3_GADGET
>   or USB_DWC3_DUAL_ROLE is selectable
> - updated commit message
> 
> Changes in v14:
> - none
> 
> Changes in v13:
> - patch added to the series

> diff --git a/drivers/usb/host/Kconfig b/drivers/usb/host/Kconfig
> index d1d926f8f9c2..e5e612f143a1 100644
> --- a/drivers/usb/host/Kconfig
> +++ b/drivers/usb/host/Kconfig
> @@ -80,7 +80,7 @@ config USB_XHCI_MTK
>  
>  config USB_XHCI_MVEBU
>  	tristate "xHCI support for Marvell Armada 375/38x/37xx"
> -	select USB_XHCI_PLATFORM
> +	depends on USB_XHCI_PLATFORM
>  	depends on HAS_IOMEM
>  	depends on ARCH_MVEBU || COMPILE_TEST
>  	help
> @@ -112,9 +112,9 @@ config USB_EHCI_BRCMSTB
>  config USB_BRCMSTB
>  	tristate "Broadcom STB USB support"
>  	depends on (ARCH_BRCMSTB && PHY_BRCM_USB) || COMPILE_TEST
> +	depends on !USB_XHCI_HCD || USB_XHCI_PLATFORM
>  	select USB_OHCI_HCD_PLATFORM if USB_OHCI_HCD
>  	select USB_EHCI_BRCMSTB if USB_EHCI_HCD
> -	select USB_XHCI_PLATFORM if USB_XHCI_HCD
>  	help
>  	  Enables support for XHCI, EHCI and OHCI host controllers
>  	  found in Broadcom STB SoC's.

It should be pointed out that this now requires people with xHCI systems 
to actively turn on CONFIG_USB_XHCI_PLATFORM before they can enable 
CONFIG_USB_BRCMSTB.  Before, that was not necessary.  Some users might 
get confused and not realize what is needed.  Perhaps something should 
be added to the "help" text.

Alan Stern