Re: Implementation of fwnode_operations :: device_get_match_data() for software nodes?

Heikki Krogerus
2023-02-27T12:19:16Z

Hi Vladimir,

On Thu, Feb 23, 2023 at 10:37:13PM +0200, Vladimir Oltean wrote:
> Hi,
>
> I have a need to instantiate a driver written for OF which calls
> device_get_match_data(dev) to get various information based on the
> compatible string.
>
> I am creating a software node based on the following properties:
>
> struct property_entry props[2] = {
> PROPERTY_ENTRY_STRING("compatible", compatible),
> {},
> };
>
> (I see I'm not the only one doing this, some drivers/platform/x86/x86-android-tablets.c
> and drivers/platform/chrome/chromeos_laptop.c also do it)
>
> and the driver in question does begin to probe, but its match_data is
> NULL, because the operation from the title isn't implemented for
> software nodes. So probing ultimately fails.
>
> Is there some sort or reason why this doesn't exist, other than a lack
> of need?

There has not been any need for it before.

> Can someone please help me with an implementation of this feature?

Try this - I'm sorry, I don't know does it actually work:

diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c
index 1886995a0b3a3..5262b49c7c790 100644
--- a/drivers/base/swnode.c
+++ b/drivers/base/swnode.c
@@ -9,6 +9,7 @@
#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/property.h>
+#include <linux/mod_devicetable.h>
#include <linux/slab.h>

#include "base.h"
@@ -379,6 +380,25 @@ static void software_node_put(struct fwnode_handle *fwnode)
kobject_put(&swnode->kobj);
}

+static const void *
+software_node_get_match_data(const struct fwnode_handle *fwnode, const struct device *dev)
+{
+ const struct of_device_id *id;
+ const char *compat;
+
+ if (!dev->driver || !dev->driver->of_match_table)
+ return NULL;
+
+ if (fwnode_property_read_string(fwnode, "compatible", &compat))
+ return NULL;
+
+ for (id = dev->driver->of_match_table; id->compatible[0]; id++)
+ if (!strcmp(compat, id->compatible))
+ return id->data;
+
+ return NULL;
+}
+
static bool software_node_property_present(const struct fwnode_handle *fwnode,
const char *propname)
{
@@ -662,6 +682,7 @@ software_node_graph_parse_endpoint(const struct fwnode_handle *fwnode,
static const struct fwnode_operations software_node_ops = {
.get = software_node_get,
.put = software_node_put,
+ .device_get_match_data = software_node_get_match_data,
.property_present = software_node_property_present,
.property_read_int_array = software_node_read_int_array,
.property_read_string_array = software_node_read_string_array,

--
heikki