Re: Mis-use of BUS_PASS_ORDER_MIDDLE

On Tue, Apr 19, 2016 at 2:53 AM John Baldwin <jhb_at_freebsd.org> wrote:

> On Monday, April 18, 2016 11:10:12 PM Howard Su wrote:
> > I noticed several places there are code like this, especially in some arm
> > low level drivers.
> > EARLY_DRIVER_MODULE(aw_ccu, simplebus, aw_ccu_driver, aw_ccu_devclass,
> >     0, 0, BUS_PASS_BUS + BUS_PASS_ORDER_MIDDLE);
> >
> > ​I feel the usage of BUS_PASS_ORDER_MIDDLE is misused. There are another
> > macro EARLY_DRIVER_MODULE_ORDERED, which take an additional parameter
> > "order". I believe BUS_PASS_ORDER_xxx is used for that parameter.
>
> No, this is actually correct.  The _ORDERED variants actually accept a
> SI_ORDER_* value to determine how drivers contained in a single .ko file
> are registered (in particular if you have several drivers in a .ko file
> you typically want the "top-most" driver to attach last so that all the
> other drivers are ready once the actual device is attached).
>
Why not use _ORDERED here to achieve same thing?  _ORDERED(....,
SI_ORDER_LAST, BUS_PASS_BUS)?

I am thinking to add some macro like BUS_DRIVER_MODULE, INT_DRIVER_MODULE,
TIMER_DRIVER_MODULE, so that the driver can declare itself in such way. If
we can avoid usage of BUS_PASS_ORDER_XXX, the macro is much cleaner.

I am plan to do is: in autoconf phase, first load timer, int and some bus,
etc low level drivers first, then set cold=0, then load other driver to
work around the problem that driver needs special handling on cold which is
not necessary. of course, this may depends on your change of ap_startup.
thoughts?


> --
> John Baldwin
>
-- 
-Howard