Re: [PATCH v1] reset: Make optional stuff optional for all users

[Philipp Zabel <p.zabel@pengutronix.de>]

On Mon, 2017-04-03 at 14:33 +0000, Shevchenko, Andriy wrote:
> On Mon, 2017-04-03 at 17:31 +0300, Andy Shevchenko wrote:
> > On Mon, 2017-04-03 at 16:27 +0200, Philipp Zabel wrote:
> > > 
> 
> > > >  	int rstc_id;
> > > >  	int ret;
> > > >  
> > > > -	if (!node)
> > > > -		return ERR_PTR(-EINVAL);
> > > > -
> > > 
> > > This should be
> > > 
> > > 	if (!node)
> > > 		return optional ? NULL : ERR_PTR(-EINVAL);
> > > 
> > > instead. Can you confirm this works for Intel boards with DW UART? I
> > > can
> > > fix it up when applying if you agree.
> > 
> > I don't think it worth to change. I specifically checked all of_*
> > calls
> > in that function and they cope pretty nice with node == NULL.

__of_reset_control_get called with id != NULL calls
of_property_match_string first, which then returns -EINVAL if
node == NULL, which makes __of_reset_control_get return NULL if optional
or -ENOENT otherwise, even though the correct return value would be
-EINVAL in the DT case.

__of_reset_control_get called with id == NULL calls
of_parse_phandle_with_args first, which calls
__of_parse_phandle_with_args, which returns an undefined value if
np == NULL, as far as I can tell:
of_for_each_phandle first calls of_phandle_iterator_init, which, when
called with np == NULL clears the iterator structure returns -ENOENT.
The return value is ignored in the of_for_each_phandle macro, and
of_phandle_iterator_next is then called and returns -ENOENT because
it->cur == NULL, ending the loop without ever assigning a value to rc.
__of_parse_phandle_with_args then returns the uninitialized value.

The point being, instead of having to regularly forage through a number
of of_ API functions to make sure my expectations are still met, I'd
prefer to keep the check in place.

> > 
> > So, I rather to go with my initial change.
> > 
> 
> Hit Enter before closing another thought.
> 
> When you come with solution where this __of_reset_control_get() will be
> called only for node != NULL case you will not need that check either.

__of_reset_control_get is public API (via of_reset_control_get), so I
can't guarantee node != NULL even in the DT case.

> So, I would go my solution because of two benefits:
> - it fixes bug

True.

> - if will not bring ping-ponging code

Unfortunately not.

regards
Philipp