linux-kernel - Re: [PATCH v17 7/7] usb: Specify dependencies on USB_XHCI

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Date:   Tue, 16 Nov 2021 21:21:44 -0500
From:   Alan Stern <stern@...land.harvard.edu>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Felipe Balbi <balbi@...nel.org>, linux-kernel@...r.kernel.org,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Peter Chen <peter.chen@...nel.org>, linux-usb@...r.kernel.org,
        devicetree@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>,
        Roger Quadros <rogerq@...nel.org>,
        Michal Simek <michal.simek@...inx.com>,
        Ravi Chandra Sadineni <ravisadineni@...omium.org>,
        Bastien Nocera <hadess@...ess.net>,
        Andrew Lunn <andrew@...n.ch>,
        Aswath Govindraju <a-govindraju@...com>,
        Dmitry Osipenko <digetx@...il.com>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>,
        Pawel Laszczak <pawell@...ence.com>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Tony Lindgren <tony@...mide.com>,
        linux-arm-kernel@...ts.infradead.org, linux-omap@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH v17 7/7] usb: Specify dependencies on USB_XHCI_PLATFORM
 with 'depends on'

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@...omium.org>
> Reviewed-by: Roger Quadros <rogerq@...nel.org>
> Reviewed-by: Douglas Anderson <dianders@...omium.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