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In-Reply-To: <966a62da-52b6-1789-13d6-5fe06b62c7fe@marek.ca>
From:   Arnd Bergmann <arnd@arndb.de>
Date:   Thu, 28 Jul 2022 14:03:06 +0200
Message-ID: <CAK8P3a2HGYJZvcXM+9fROys5A6c40zFWD2qATT4xssSJf6hRfQ@mail.gmail.com>
Subject: Re: [PATCH 0/2] arm64 defconfig: Get faddr2line working
To:     Jonathan Marek <jonathan@marek.ca>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        John Garry <john.garry@huawei.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Olof Johansson <olof@lixom.net>, SoC Team <soc@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Vinod Koul <vkoul@kernel.org>
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On Thu, Jul 28, 2022 at 1:57 PM Jonathan Marek <jonathan@marek.ca> wrote:
> On 7/28/22 5:09 AM, Arnd Bergmann wrote:
> > diff --git a/drivers/soundwire/qcom.c b/drivers/soundwire/qcom.c
> > index 22b706350ead..f65c7737c2db 100644
> > --- a/drivers/soundwire/qcom.c
> > +++ b/drivers/soundwire/qcom.c
> > @@ -1289,11 +1289,7 @@ static int qcom_swrm_probe(struct platform_device *pdev)
> >          data = of_device_get_match_data(dev);
> >          ctrl->rows_index = sdw_find_row_index(data->default_rows);
> >          ctrl->cols_index = sdw_find_col_index(data->default_cols);
> > -#if IS_REACHABLE(CONFIG_SLIMBUS)
> > -       if (dev->parent->bus == &slimbus_bus) {
> > -#else
> > -       if (false) {
> > -#endif
> > +       if (IS_ENABLED(CONFIG_SLIMBUS) && dev->parent->bus == &slimbus_bus) {
> >                  ctrl->reg_read = qcom_swrm_ahb_reg_read;
> >                  ctrl->reg_write = qcom_swrm_ahb_reg_write;
> >                  ctrl->regmap = dev_get_regmap(dev->parent, NULL);
> >
>
> This relies on the compiler optimizing out the reference to slimbus_bus,
> which doesn't exist in the CONFIG_SLIMBUS=n case (not tested, but I
> think this means an O0 build will fail?).

That is correct: We rely on this everywhere in the kernel, which is why
it is impossible to build kernels with -O0.

       Arnd