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

From: Matthias Kaehlcke <mka@chromium.org>
To: Dmitry Osipenko <digetx@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Alan Stern <stern@rowland.harvard.edu>,
	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>,
	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: Mon, 20 Dec 2021 10:44:55 -0800	[thread overview]
Message-ID: <YcDPJ1POD5oAqyLj@google.com> (raw)
In-Reply-To: <b0b69294-e7fb-5e7a-80f3-466dd4bdc88a@gmail.com>

On Fri, Dec 17, 2021 at 03:47:24AM +0300, Dmitry Osipenko wrote:
> 17.12.2021 02:56, Matthias Kaehlcke пишет:
> > 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>
> > 
> > Note: This patch has been removed from the onboard_usb_hub series,
> > together with "ARM: configs: Explicitly enable USB_XHCI_PLATFORM
> > where needed" and "arm64: defconfig: Explicitly enable
> > USB_XHCI_PLATFORM". These patches aren't any longer needed for the
> > series. If maintainers think they are useful independently from
> > the series please pick them or let me know what needs to be
> > changed to get them landed.
> > 
> 
> Hi,
> 
> I don't know what this all is about, perhaps I'm CC'ed semi-randomly
> because touched that Kconfig once.

Yes, it seems tools select you based on their heuristics because you
made changes to that file.

> All I can say here is that the commit message tells us "This is not
> recommended" and doesn't explain what's the actual problem is being
> solved. If there is no real problem, why bother?

Earlier versions of the onboard_usb_hub series [1] which had a dependency
involving USB_XHCI_PLATFORM had an issue with invalid (rand)configs
that was related with the 'selects'.

The series doesn't depend on USB_XHCI_PLATFORM any longer, hence the
original issue doesn't exist anymore, however it might re-surface in
the future.

Personally I have no vested interest at this point in getting the
config changes landed, I just wanted to make clear what the status
is (split off from the series, no future versions unless someone
requests them), rather than abandoning them silently.

[1]: https://patchwork.kernel.org/project/linux-usb/list/?series=531343