Re: [PATCH] gpiolib: handle probe deferrals better

[Guenter Roeck <linux@roeck-us.net>]

On Fri, Apr 01, 2016 at 03:03:40PM +0200, Linus Walleij wrote:
> On Fri, Apr 1, 2016 at 2:16 PM, Alexander Stein
> <alexander.stein@systec-electronic.com> wrote:
> 
> > I noticed you fiddle with late_initcall_sync. Sorry, I did not mention it:
> > gpio_mcp23s08 as well as gpio_keys are loaded as modules, so late_initcall_*
> > should not affect it.
> 
> I don't get this. I think probe deferral is only used to defer
> initcalls used for built-in drivers.
> 

Maybe late_initcall() and driver_probe_done() are not synchronous ?

In other words, is it guaranteed that driver_probe_done() returns
true when late_initcall() is executed ?

Thanks,
Guenter

> If there are dependencies among things compiled as modules,
> doesn't depmod/modprobe make sure that they are probed in
> the right order? Could it be that some module alias thingofabob
> is missing?
> 
> Or is modprobe failing because it (correctly) see that there is
> no symbol dependencies between the gpio_mcp23s08 and
> gpio-keys modules? (Not that I know how depmod works...)
> 
> If nothing else works, I guess marking mcp23s08 as bool
> and building it into the kernel will work, right?
> 
> Yours,
> Linus Walleij