Re: [PATCH] usb: ulpi: don't register drivers if bus doesn't exist

Heikki Krogerus
2015-05-25T11:42:25Z

Hi,

> Why do we even need that? If you take patch that makes ulpi_init a
> subsys_initcall you won't have this problem, and no additional weird
> hacks and errors will be needed

Using subsys_initcall will work around the problem for now, but I
would not make the assumption that there will never be ulpi phy
drivers and ulpi interface drivers that don't use subsys_initcall
themselves. By checking the old phy drivers at drivers/usb/phy/, at
least so far it hasn't been uncommon for them to use subsys_initcall.

I would much prefer to have a proper fix for this issue instead of
just working around it, but we need to use subsys_initcall in any
case.

> >> > + /* Was the bus registered successfully? */
> >> > + if (!ulpi_bus.p)
> >> > + return -ENODEV;
> >>
> >> Ick, no, don't go mucking around in the bus internals like this, that's
> >> not ok. You should either "know" the bus is registered, or something is
> >> really wrong with the design here.
> > can't we use a variable which can be initialized to 1 in ulpi_init() if
> > the bus registers successfully and later check that?

Just a note. We should also be aware if the bus registration failed or
if it just hasn't been loaded yet.

If we used a variable like that, I guess it could initially have the
value -EAGAIN. If bus_register returns error, we store -ENODEV to it.
If bus_register succeeds we store 0 to it. I don't know if we can just
store the return value from bus_register to it.

In ulpi_register_driver and ulpi_register_interface we can then just
return it if it has a value other then 0.

But couldn't we add a helper function to drivers/base/bus.c that the
bus drivers can use to at least check was the bus already loaded or
not? It looks like there are a couple of bus drivers that use the
struct bus member "p" to check that.

Greg, what do you think?

Thanks,

--
heikki