Re: [PATCH 3/8] device property: Helper to match multiple connections

On 28-12-21, 09:04, Bjorn Andersson wrote:

On Tue 28 Dec 05:09 PST 2021, Dmitry Baryshkov wrote:

quoted

On 28/12/2021 08:21, Bjorn Andersson wrote:

quoted

In some cases multiple connections with the same connection id
needs to be resolved from a fwnode graph.

One such example is when separate hardware is used for performing muxing and/or
orientation switching of the SuperSpeed and SBU lines in a USB-C
connector. In this case the connector needs to belong to a graph with
multiple matching remote endpoints, and the TypeC controller needs to be
able to resolve them both.

Add a new API that allows this kind of lookup.

Signed-off-by: Bjorn Andersson <redacted>
---
  drivers/base/property.c  | 94 ++++++++++++++++++++++++++++++++++++++++
  include/linux/property.h |  5 +++
  2 files changed, 99 insertions(+)

diff --git a/drivers/base/property.c b/drivers/base/property.c
index cbe4fa298413..0aa0296fd991 100644
--- a/drivers/base/property.c
+++ b/drivers/base/property.c

@@ -1180,6 +1180,36 @@ fwnode_graph_devcon_match(struct fwnode_handle *fwnode, const char *con_id,
  	return NULL;
  }
+static unsigned int fwnode_graph_devcon_matches(struct fwnode_handle *fwnode,
+						const char *con_id, void *data,
+						devcon_match_fn_t match,
+						void **matches,
+						unsigned int matches_len)
+{
+	struct fwnode_handle *node;
+	struct fwnode_handle *ep;
+	unsigned int count = 0;
+	void *ret;
+
+	fwnode_graph_for_each_endpoint(fwnode, ep) {
+		if (count >= matches_len) {
+			fwnode_handle_put(ep);
+			return count;
+		}
+
+		node = fwnode_graph_get_remote_port_parent(ep);
+		if (!fwnode_device_is_available(node))
+			continue;
+
+		ret = match(node, con_id, data);
+		fwnode_handle_put(node);
+
+		if (ret)
+			matches[count++] = ret;
+	}
+	return count;
+}

This API doesn't let it's user know if there are more matches found in the
device tree or not. I'd suggest to add 'count' mode that would return the
amount of found matches if (matches == NULL) && (matches_len == 0).

But the API does call each match

Unfortunately in this code path we don't know how to "free" the objects
returned by match(), e.g. see how typec_switch_match() returns wrapper
of a refcounted device.

So we must return all the match results to the caller to it can free
things up based on its knowledge of what matches[] actually contains..

ACPI walk has similar APIs, I can think of acpi_walk_namespace() which I
have used in past and does similar walk in namespace but for devices and
calls the match()

-- 
~Vinod