Messages in this thread | | | From | Rob Herring <> | Date | Thu, 24 May 2018 15:57:54 -0500 | Subject | Re: [PATCH v2 1/8] driver core: make deferring probe after init optional |
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On Thu, May 24, 2018 at 2:00 PM, Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote: > 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) { > > Wait, what's the "optional" mess here?
My intent was that subsystems just always call this function and never return EPROBE_DEFER themselves. Then the driver core can make decisions as to what to do (such as the timeout added in the next patch). Or it can print common error/debug messages. So optional is a hint to allow subsystems per device control.
> > The caller knows this value, so why do you need to even pass it in here?
Because regardless of the value, we always stop deferring when/if we hit the timeout and the caller doesn't know about the timeout. If we get rid of it, we'd need functions for both init done and for deferred timeout.
> And bool values that are not obvious are horrid. I had to go look this > up when reading the later patches that just passed "true" in this > variable as I had no idea what that meant.
Perhaps inverting it and calling it "keep_deferring" would be better. However, the flag is ignored if we have timed out.
> > So as-is, no, this isn't ok, sorry. > > And at the least, this needs some kerneldoc to explain it :)
That part is easy enough to fix.
Rob
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