On Sat, Nov 30, 2024 at 11:44:04PM +0200, Andy Shevchenko wrote:
> On Fri, Nov 29, 2024 at 11:16:54PM -0800, Dmitry Torokhov wrote:
> > On Fri, Nov 29, 2024 at 04:50:15PM +0200, Andy Shevchenko wrote:
> > > On Thu, Nov 28, 2024 at 03:04:50PM -0800, Dmitry Torokhov wrote:
> > > > On Thu, Nov 28, 2024 at 03:13:16PM +0200, Andy Shevchenko wrote:
> > > > > On Wed, Nov 27, 2024 at 09:39:34PM -0800, Dmitry Torokhov wrote:
>
> ...
>
> > > > > > @@ struct fwnode_handle *device_get_next_child_node(const struct device *dev,
> > > > > > const struct fwnode_handle *fwnode = dev_fwnode(dev);
> > > > > > struct fwnode_handle *next;
> > > > >
> > > > > > - if (IS_ERR_OR_NULL(fwnode))
> > > > > > + if (IS_ERR_OR_NULL(fwnode)) {
> > > > > > + fwnode_handle_put(child);
> > > > > > return NULL;
> > > > > > + }
> > > > >
> > > > > > /* Try to find a child in primary fwnode */
> > > > > > next = fwnode_get_next_child_node(fwnode, child);
> > > > >
> > > > > So, why not just moving the original check (w/o dropping the reference) here?
> > > > > Wouldn't it have the same effect w/o explicit call to the fwnode_handle_put()?
> > > >
> > > > Because if you rely on check in fwnode_get_next_child_node() you would
> > > > not know if it returned NULL because there are no more children or
> > > > because the node is invalid. In the latter case you can't dereference
> > > > fwnode->secondary.
> > >
> > > Yes, so, how does it contradict my proposal?
> >
> > I guess I misunderstood your proposal then. Could you please explain it
> > in more detail?
>
>
> Current code (in steps):
> if (IS_ERR_OR_NULL()) check
> trying primary
> trying secondary if previous is NULL
>
>
> My proposal
>
> trying primary
> return if not NULL
> if (IS_ERR_OR_NULL()) check in its current form (no put op)
> trying secondary
>
> After your first patch IIUC this is possible as trying primary will put child uncoditionally.
Ah, I see. No, I do not think this is a good idea: it will make the code
harder to understand for a casual reader: "Why do we check node validity
only after we used it for the first time?"
For the code not in a hot path there is a lot of value in simplicity.
Thanks.
--
Dmitry
