From: Sakari Ailus <sakari.ailus@linux.intel.com>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Petr Mladek <pmladek@suse.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
Rob Herring <robh@kernel.org>
Subject: Re: [PATCH v2 1/6] device property: Add functions for accessing node's parents
Date: Fri, 29 Mar 2019 15:15:07 +0200 [thread overview]
Message-ID: <20190329131507.cc4qt5oyd74nvmzt@kekkonen.localdomain> (raw)
In-Reply-To: <CAJZ5v0gAM_jn-gkmyu7Av+X0W_8g9NGjBEeXC-3-q_Ncb2PEGw@mail.gmail.com>
On Thu, Mar 28, 2019 at 03:52:35PM +0100, Rafael J. Wysocki wrote:
> On Thu, Mar 28, 2019 at 12:13 PM Sakari Ailus
> <sakari.ailus@linux.intel.com> wrote:
> >
> > Hi Rafael,
> >
> > On Thu, Mar 28, 2019 at 10:38:01AM +0100, Rafael J. Wysocki wrote:
> > > On Wed, Mar 27, 2019 at 3:20 PM Sakari Ailus
> > > <sakari.ailus@linux.intel.com> wrote:
> > > >
> > > > Hi Petr,
> > > >
> > > > On Wed, Mar 27, 2019 at 01:26:25PM +0100, Petr Mladek wrote:
> > > > > On Tue 2019-03-26 14:41:01, Sakari Ailus wrote:
> > > > > > Add two convenience functions for accessing node's parents:
> > > > > >
> > > > > > fwnode_count_parents() returns the number of parent nodes a given node
> > > > > > has. fwnode_get_nth_parent() returns node's parent at a given distance
> > > > > > from the node itself.
> > > > > >
> > > > > > Also reorder fwnode_get_parent() in property.c according to the same order
> > > > > > as in property.h.
> > > > > >
> > > > > > diff --git a/drivers/base/property.c b/drivers/base/property.c
> > > > > > index 8b91ab380d14..61eb6ceacc3f 100644
> > > > > > --- a/drivers/base/property.c
> > > > > > +++ b/drivers/base/property.c
> > > > > > @@ -554,17 +567,49 @@ struct fwnode_handle *fwnode_get_next_parent(struct fwnode_handle *fwnode)
> > > > > > EXPORT_SYMBOL_GPL(fwnode_get_next_parent);
> > > > > >
> > > > > > /**
> > > > > > - * fwnode_get_parent - Return parent firwmare node
> > > > > > - * @fwnode: Firmware whose parent is retrieved
> > > > > > + * fwnode_count_parents - Return the number of parents a node has
> > > > > > + * @fwnode: The node the parents of which are to be counted
> > > > > > *
> > > > > > - * Return parent firmware node of the given node if possible or %NULL if no
> > > > > > - * parent was available.
> > > > > > + * Returns the number of parents a node has.
> > > > > > */
> > > > > > -struct fwnode_handle *fwnode_get_parent(const struct fwnode_handle *fwnode)
> > > > > > +unsigned int fwnode_count_parents(struct fwnode_handle *fwnode)
> > > > > > {
> > > > > > - return fwnode_call_ptr_op(fwnode, get_parent);
> > > > > > + unsigned int count;
> > > > > > +
> > > > > > + fwnode_handle_get(fwnode);
> > > > > > +
> > > > > > + for (count = 0; fwnode; count++)
> > > > > > + fwnode = fwnode_get_next_parent(fwnode);
> > > > >
> > > > > Is it guaranteed that all parents stay when
> > > > > fwnode_get_next_parent() releases the reference count
> > > > > for each counted member?
> > > >
> > > > fwnode_get_next_parent() only releases the child node after it has acquired
> > > > the parent. The only implementation with refcounting for single nodes is
> > > > actually OF.
> > > >
> > > > >
> > > > > > +
> > > > > > + return count - 1;
> > > > >
> > > > > We could start counting from count = -1;
> > > >
> > > > We could, but then count would need to be made signed (unless overflowing
> > > > is preferred instead).
> > >
> > > What if there are no parents?
> > >
> > > Or is it guaranteed that there always will be at least one?
> >
> > If there are no parents, the function will return 0 --- the node itself is
> > counted in the loop, too, hence the need to decrement by one.
>
> Right, sorry.
>
> Then I don't see why count cannot be int. Or call it "iter" to avoid
> confusion with negative "counts". :-)
Another option would be changing where the counting starts --- the first
parent. I.e.
fwnode = fwnode_get_parent(fwnode);
for (count = 0; fwnode; count++)
fwnode = fwnode_get_next_parent(fwnode);
return count;
--
Sakari Ailus
sakari.ailus@linux.intel.com
next prev parent reply other threads:[~2019-03-29 13:15 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-26 12:41 [PATCH v2 0/6] Device property improvements, add %pfw format specifier Sakari Ailus
2019-03-26 12:41 ` [PATCH v2 1/6] device property: Add functions for accessing node's parents Sakari Ailus
2019-03-27 12:26 ` Petr Mladek
2019-03-27 14:20 ` Sakari Ailus
2019-03-28 9:38 ` Rafael J. Wysocki
2019-03-28 11:13 ` Sakari Ailus
2019-03-28 14:52 ` Rafael J. Wysocki
2019-03-29 13:15 ` Sakari Ailus [this message]
2019-03-29 14:15 ` Andy Shevchenko
2019-03-29 14:46 ` Sakari Ailus
2019-03-29 23:00 ` Rafael J. Wysocki
2019-03-28 14:10 ` Petr Mladek
2019-03-29 13:04 ` Sakari Ailus
2019-03-29 14:14 ` Andy Shevchenko
2019-03-29 15:31 ` Sakari Ailus
2019-03-26 12:41 ` [PATCH v2 2/6] device property: Add fwnode_get_name for returning the name of a node Sakari Ailus
2019-03-28 9:45 ` Rafael J. Wysocki
2019-03-28 11:31 ` Sakari Ailus
2019-03-31 6:42 ` Rob Herring
2019-03-26 12:41 ` [PATCH v2 3/6] device property: Add a function to obtain a node's prefix Sakari Ailus
2019-03-26 13:16 ` Andy Shevchenko
2019-03-26 13:32 ` Sakari Ailus
2019-03-27 12:36 ` Petr Mladek
2019-03-28 11:43 ` Sakari Ailus
2019-03-31 6:42 ` Rob Herring
2019-03-26 12:41 ` [PATCH v2 4/6] lib/vsprintf: Remove support for %pF and %pf in favour of %pS and %ps Sakari Ailus
2019-03-26 12:41 ` [PATCH v2 5/6] lib/vsprintf: Make use of fwnode API to obtain node names and separators Sakari Ailus
2019-03-26 12:41 ` [PATCH v2 6/6] lib/vsprintf: Add %pfw conversion specifier for printing fwnode names Sakari Ailus
2019-03-26 13:11 ` Rasmus Villemoes
2019-03-26 13:24 ` Andy Shevchenko
2019-03-26 13:31 ` Sakari Ailus
2019-03-28 14:29 ` Petr Mladek
2019-03-29 13:10 ` Sakari Ailus
2019-03-26 20:18 ` Joe Perches
[not found] ` <20190328114845.giusyarjibvg5ru7@kekkonen.localdomain>
2019-03-28 11:51 ` Sakari Ailus
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