Re: [PATCH v1 12/18] driver core: Add fw_devlink_parse_fwtree()

Saravana Kannan
2020-11-21T02:01:14Z

On Mon, Nov 16, 2020 at 8:25 AM Rafael J. Wysocki <rafael@kernel.org> wrote:
>
> On Thu, Nov 5, 2020 at 12:24 AM Saravana Kannan <saravanak@google.com> wrote:
> >
> > This function is a wrapper around fwnode_operations.add_links().
> >
> > This function parses each node in a fwnode tree and create fwnode links
> > for each of those nodes. The information for creating the fwnode links
> > (the supplier and consumer fwnode) is obtained by parsing the properties
> > in each of the fwnodes.
> >
> > This function also ensures that no fwnode is parsed more than once by
> > marking the fwnodes as parsed.
> >
> > Signed-off-by: Saravana Kannan <saravanak@google.com>
> > ---
> > drivers/base/core.c | 19 +++++++++++++++++++
> > include/linux/fwnode.h | 3 +++
> > 2 files changed, 22 insertions(+)
> >
> > diff --git a/drivers/base/core.c b/drivers/base/core.c
> > index 4a0907574646..ee28d8c7ee85 100644
> > --- a/drivers/base/core.c
> > +++ b/drivers/base/core.c
> > @@ -1543,6 +1543,25 @@ static bool fw_devlink_is_permissive(void)
> > return fw_devlink_flags == DL_FLAG_SYNC_STATE_ONLY;
> > }
> >
> > +static void fw_devlink_parse_fwnode(struct fwnode_handle *fwnode)
> > +{
> > + if (fwnode->flags & FWNODE_FLAG_LINKS_ADDED)
> > + return;
>
> Why is the flag needed?
>
> Duplicate links won't be created anyway and it doesn't cause the tree
> walk to be terminated.

To avoid parsing a fwnode more than once. The cumulative impact of the
repeated parsing is actually quite high.

And I intentionally didn't do this check at the tree walk level
because DT overlay can add/remove/change individual fwnodes and I want
to reparse those when they are added while avoiding parsing other
nodes that have already been parsed and not changed by DT overlay.

>
> > +
> > + fwnode_call_int_op(fwnode, add_links, NULL);
> > + fwnode->flags |= FWNODE_FLAG_LINKS_ADDED;
> > +}
> > +
> > +static void fw_devlink_parse_fwtree(struct fwnode_handle *fwnode)
> > +{
> > + struct fwnode_handle *child = NULL;
> > +
> > + fw_devlink_parse_fwnode(fwnode);
> > +
> > + while ((child = fwnode_get_next_available_child_node(fwnode, child)))
>
> I'd prefer
>
> for (child = NULL; child; child =
> fwnode_get_next_available_child_node(fwnode, child))

I was about to change to this and then realized it won't work. It
would have to be

for (child = fwnode_get_next_available_child_node(fwnode, NULL));
child;
child = fwnode_get_next_available_child_node(fwnode, child))

Is that really better? The while() seems a lot more readable to me. I
don't have a strong opinion, so I'll go with whatever you say after
reading this.

>
> > + fw_devlink_parse_fwtree(child);
> > +}
> > +
> > static void fw_devlink_link_device(struct device *dev)
> > {
> > int fw_ret;
> > diff --git a/include/linux/fwnode.h b/include/linux/fwnode.h
> > index ec02e1e939cc..9aaf9e4f3994 100644
> > --- a/include/linux/fwnode.h
> > +++ b/include/linux/fwnode.h
> > @@ -15,12 +15,15 @@
> > struct fwnode_operations;
> > struct device;
> >
>
> Description here, please.

Ack

>
> > +#define FWNODE_FLAG_LINKS_ADDED BIT(0)
> > +
> > struct fwnode_handle {
> > struct fwnode_handle *secondary;
> > const struct fwnode_operations *ops;
> > struct device *dev;
> > struct list_head suppliers;
> > struct list_head consumers;
> > + u32 flags;
>
> That's a bit wasteful. Maybe u8 would suffice for the time being?

Ack.

-Saravana