linux-kernel - Re: [PATCH v10 0/5] USB: misc: Add onboard_usb

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Message-ID: <YK03AVRfbRJUGd0X@google.com>
Date:   Tue, 25 May 2021 10:42:25 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Alan Stern <stern@...land.harvard.edu>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Michal Simek <michal.simek@...inx.com>,
        devicetree@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>,
        linux-usb@...r.kernel.org, Peter Chen <peter.chen@...nel.org>,
        linux-kernel@...r.kernel.org, Stephen Boyd <swboyd@...omium.org>,
        Ravi Chandra Sadineni <ravisadineni@...omium.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Bastien Nocera <hadess@...ess.net>,
        Al Cooper <alcooperx@...il.com>,
        "Alexander A. Klimov" <grandmaster@...klimov.de>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Christian Lamparter <chunkeey@...glemail.com>,
        Colin Ian King <colin.king@...onical.com>,
        Dmitry Osipenko <digetx@...il.com>,
        Fabio Estevam <festevam@...il.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Vinod Koul <vkoul@...nel.org>, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v10 0/5] USB: misc: Add onboard_usb_hub driver

On Fri, May 21, 2021 at 02:30:39PM +0200, Greg Kroah-Hartman wrote:
> On Tue, May 11, 2021 at 03:52:18PM -0700, Matthias Kaehlcke wrote:
> > This series adds:
> > - the onboard_usb_hub_driver
> > - glue in the xhci-plat driver to create the onboard_usb_hub
> >   platform device if needed
> > - a device tree binding for the Realtek RTS5411 USB hub controller
> > - device tree changes that add RTS5411 entries for the QCA SC7180
> >   based boards trogdor and lazor
> > - a couple of stubs for platform device functions to avoid
> >   unresolved symbols with certain kernel configs
> > 
> > The main issue the driver addresses is that a USB hub needs to be
> > powered before it can be discovered. For discrete onboard hubs (an
> > example for such a hub is the Realtek RTS5411) this is often solved
> > by supplying the hub with an 'always-on' regulator, which is kind
> > of a hack. Some onboard hubs may require further initialization
> > steps, like changing the state of a GPIO or enabling a clock, which
> > requires even more hacks. This driver creates a platform device
> > representing the hub which performs the necessary initialization.
> > Currently it only supports switching on a single regulator, support
> > for multiple regulators or other actions can be added as needed.
> > Different initialization sequences can be supported based on the
> > compatible string.
> > 
> > Besides performing the initialization the driver can be configured
> > to power the hub off during system suspend. This can help to extend
> > battery life on battery powered devices which have no requirements
> > to keep the hub powered during suspend. The driver can also be
> > configured to leave the hub powered when a wakeup capable USB device
> > is connected when suspending, and power it off otherwise.
> 
> I get a build error when I apply this series to my tree:
> 
> drivers/usb/misc/onboard_usb_hub.c:273:6: error: redefinition of ‘of_is_onboard_usb_hub’
>   273 | bool of_is_onboard_usb_hub(const struct device_node *np)
>       |      ^~~~~~~~~~~~~~~~~~~~~
> In file included from drivers/usb/misc/onboard_usb_hub.c:21:
> ./include/linux/usb/onboard_hub.h:9:20: note: previous definition of ‘of_is_onboard_usb_hub’ with type ‘bool(const struct device_node *)’ {aka ‘_Bool(const struct device_node *)’}
>     9 | static inline bool of_is_onboard_usb_hub(const struct device_node *np)
>       |                    ^~~~~~~~~~~~~~~~~~~~~
> 
> Any thoughts?

That function keeps haunting me in different ways ...

I suspect this was a build with CONFIG_COMPILE_TEST=y. The driver is
compiled for such a config and has the actual implementation, however
the header defines the static inline unless CONFIG_USB_ONBOARD_HUB=y/m.

I realized earlier that the driver doesn't really need to include the
header, and planned to remove it in the next version, which might be
the most practical solution.