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    SubjectRe: [PATCH v2 1/8] driver core: make deferring probe after init optional
    On Thu, May 24, 2018 at 12:50:17PM -0500, Rob Herring wrote:
    > Deferred probe will currently wait forever on dependent devices to probe,
    > but sometimes a driver will never exist. It's also not always critical for
    > a driver to exist. Platforms can rely on default configuration from the
    > bootloader or reset defaults for things such as pinctrl and power domains.
    > This is often the case with initial platform support until various drivers
    > get enabled. There's at least 2 scenarios where deferred probe can render
    > a platform broken. Both involve using a DT which has more devices and
    > dependencies than the kernel supports. The 1st case is a driver may be
    > disabled in the kernel config. The 2nd case is the kernel version may
    > simply not have the dependent driver. This can happen if using a newer DT
    > (provided by firmware perhaps) with a stable kernel version.
    >
    > Subsystems or drivers may opt-in to this behavior by calling
    > driver_deferred_probe_check_init_done() instead of just returning
    > -EPROBE_DEFER. They may use additional information from DT or kernel's
    > config to decide whether to continue to defer probe or not.
    >
    > Cc: Alexander Graf <agraf@suse.de>
    > Signed-off-by: Rob Herring <robh@kernel.org>
    > ---
    > drivers/base/dd.c | 17 +++++++++++++++++
    > include/linux/device.h | 2 ++
    > 2 files changed, 19 insertions(+)
    >
    > diff --git a/drivers/base/dd.c b/drivers/base/dd.c
    > index c9f54089429b..d6034718da6f 100644
    > --- a/drivers/base/dd.c
    > +++ b/drivers/base/dd.c
    > @@ -226,6 +226,16 @@ void device_unblock_probing(void)
    > driver_deferred_probe_trigger();
    > }
    >
    > +int driver_deferred_probe_check_init_done(struct device *dev, bool optional)
    > +{
    > + if (optional && initcalls_done) {
    > + dev_WARN(dev, "ignoring dependency for device, assuming no driver");

    You really only need dev_warn(), here, right?

    thanks,

    greg k-h

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