[PATCH 3/5] of/device: Make of_get_next_child() check status properties
Michael Ellerman
michael at ellerman.id.au
Thu Dec 16 09:40:55 EST 2010
On Wed, 2010-12-15 at 10:35 -0800, Hollis Blanchard wrote:
> On Wed, Dec 8, 2010 at 7:09 PM, David Gibson
> <david at gibson.dropbear.id.au> wrote:
> > On Thu, Dec 09, 2010 at 12:33:22PM +1100, Michael Ellerman wrote:
> >> On Wed, 2010-12-08 at 15:01 -0600, Scott Wood wrote:
> >> > On Wed, 8 Dec 2010 11:29:44 -0800
> >> > Deepak Saxena <deepak_saxena at mentor.com> wrote:
> >> >
> >> > > We only return the next child if the device is available.
> >> > >
> >> > > Signed-off-by: Hollis Blanchard <hollis_blanchard at mentor.com>
> >> > > Signed-off-by: Deepak Saxena <deepak_saxena at mentor.com>
> >> > > ---
> >> > > drivers/of/base.c | 4 +++-
> >> > > 1 files changed, 3 insertions(+), 1 deletions(-)
> >> > >
> >> > > diff --git a/drivers/of/base.c b/drivers/of/base.c
> >> > > index 5d269a4..81b2601 100644
> >> > > --- a/drivers/of/base.c
> >> > > +++ b/drivers/of/base.c
> >> > > @@ -321,6 +321,8 @@ struct device_node *of_get_next_parent(struct device_node *node)
> >> > > *
> >> > > * Returns a node pointer with refcount incremented, use
> >> > > * of_node_put() on it when done.
> >> > > + *
> >> > > + * Does not return nodes marked unavailable by a status property.
> >> > > */
> >> > > struct device_node *of_get_next_child(const struct device_node *node,
> >> > > struct device_node *prev)
> >> > > @@ -330,7 +332,7 @@ struct device_node *of_get_next_child(const struct device_node *node,
> >> > > read_lock(&devtree_lock);
> >> > > next = prev ? prev->sibling : node->child;
> >> > > for (; next; next = next->sibling)
> >> > > - if (of_node_get(next))
> >> > > + if (of_device_is_available(next) && of_node_get(next))
> >> > > break;
> >> > > of_node_put(prev);
> >> > > read_unlock(&devtree_lock);
> >> >
> >> > This seems like too low-level a place to put this. Some code may know
> >> > how to un-disable a device in certain situations, or it may be part of
> >> > debug code trying to dump the whole device tree, etc. Looking
> >> > further[1], I see a raw version of this function, but not other things
> >> > like of_find_compatible_node.
> >>
> >> Yeah I agree. I think we'll eventually end up with __ versions of all or
> >> lots of them. Not to mention there might be cases you've missed where
> >> code expects to see unavailable nodes. The right approach is to add
> >> _new_ routines that don't return unavailable nodes, and convert code
> >> that you know wants to use them.
> >
> > Actually, I don't think we really want these status-skipping
> > iterators at all. The device tree iterators should give us the device
> > tree, as it is. Those old-style drivers which seach for a node rather
> > than using the bus probing logic can keep individual checks of the
> > status property until they're converted to the new scheme.
>
> So the patch should look something like this?
>
> @@ -321,6 +321,8 @@ struct device_node *of_get_next_parent(struct
> device_node *node)
> *
> * Returns a node pointer with refcount incremented, use
> * of_node_put() on it when done.
> + *
> + * Do not use this function.
> */
> struct device_node *of_get_next_child(const struct device_node *node,
> struct device_node *prev)
Haha. No it should say "this function doesn't lie to you".
And the patch should say "this patch _doesn't_ subtly change all callers
of of_get_next_child() without carefully auditing them".
cheers
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