Re: [PATCH] media: ipu3: add a module to probe sensors via ACPI

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Hi Heikki

On 26/05/2020 15:31, Heikki Krogerus wrote:
On Fri, May 22, 2020 at 11:57:36AM +0200, Mauro Carvalho Chehab wrote:
Em Thu, 21 May 2020 11:00:19 +0300
Andy Shevchenko <andy.shevchenko@xxxxxxxxx> escreveu:

+Cc: Heikki (swnode expert)

On Wed, May 20, 2020 at 2:19 PM Mauro Carvalho Chehab
<mchehab+huawei@xxxxxxxxxx> wrote:
Em Wed, 20 May 2020 11:26:08 +0300
Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx> escreveu:

...

As I said, the problem is not probing the sensor via ACPI, but, instead,
to be able receive platform-specific data.

There is no problem with swnodes, except missing parts (*).
I have Skylake laptop with IPU3 and with half-baked ACPI tables, but
since we have drivers in place with fwnode support, we only need to
recreate fwnode graph in some board file to compensate the gap in
ACPI.

*) Missing part is graph support for swnodes. With that done it will
be feasible to achieve the rest.
I forgot if we have anything for this already done. Heikki?

Hmm... I guess I should try this approach. I never heard about swnodes
before. Do you have already some patch with the needed swnodes setup,
and the missing parts to recreate the fwnode graph?

Here you go. I tested it with this code:

         static const struct software_node nodes[];

         static const struct property_entry ep0_props[] = {
                PROPERTY_ENTRY_REF("remote-endpoint", &nodes[5]),
                { }
         };

         static const struct property_entry ep1_props[] = {
                PROPERTY_ENTRY_REF("remote-endpoint", &nodes[2]),
                { }
         };

         static const struct software_node nodes[] = {
                { "dev0" },
                { "port0", &nodes[0] },
                { "endpoint", &nodes[1], ep0_props },
                { "dev1" },
                { "port0", &nodes[3] },
                { "endpoint", &nodes[4], ep1_props },
                { }
         };

         void test(void)
         {
                 const struct software_node *swnode;
                 struct fwnode_handle *fwnode;

                 software_node_register_nodes(nodes);

                 fwnode = fwnode_graph_get_remote_port_parent(software_node_fwnode(&nodes[5]));
                 swnode = to_software_node(fwnode);
                 printk("first parent: %s\n", swnode->name);

                 fwnode = fwnode_graph_get_remote_port_parent(software_node_fwnode(&nodes[2]));
                 swnode = to_software_node(fwnode);
                 printk("second parent: %s\n", swnode->name);

                 software_node_unregister_nodes(nodes);
         }

thanks,


One of the problems we're having trying to build (using the changes you attached here) a module to connect sensors to the cio2 infrastructure is that we can't unload it cleanly. There seems to be a couple of reasons for that; but one of them is that cio2_parse_firmware() in ipu3-cio2.c ticks up the refcount for fwnode_handles of the ports for the CIO2 device by calling software_node_graph_get_next_endpoint() once per _possible_ cio2 port; each time that happens it gets a reference to the port's fwnode_handle but doesn't release it.

This isn't really a patch as such, since I don't think the changes you attached are actually applied either upstream or in the media_tree git (what are the plans in that regard, by the way? Will that patch be sent upstream at some point?) so there's nowhere to apply it to, but I think something like the below fixes it.

What do you think?

Regards,
Dan

---
diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c
index 3667467196f0..62a1e3de8cb3 100644
--- a/drivers/base/swnode.c
+++ b/drivers/base/swnode.c
@@ -584,7 +584,9 @@ software_node_graph_get_next_endpoint(const struct fwnode_handle *fwnode,
                endpoint = software_node_get_next_child(port, old);
                fwnode_handle_put(old);
                if (endpoint)
-                       break;
+                       break;
+               else
+                       fwnode_handle_put(port);
        }

        fwnode_handle_put(port);
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