Re: [RFC PATCH] net: devlink: devlink_nl_info_fill: populate default information

Some piece of information are common to the vast majority of the
devices. Examples are:

 * the driver name.
 * the serial number of a USB device.

Modify devlink_nl_info_fill() to retrieve those information so that
the drivers do not have to. Rationale: factorize code.

Signed-off-by: Vincent Mailhol <redacted>
---
I am sending this as an RFC because I just started to study devlink.

I can see a parallel with ethtool for which the core will fill
whatever it can. c.f.:
commit f20a0a0519f3 ("ethtool: doc: clarify what drivers can implement in their get_drvinfo()")
Link: https://git.kernel.org/netdev/net-next/c/f20a0a0519f3

I think that devlink should do the same.

Right now, I identified two fields. If this RFC receive positive
feedback, I will iron it up and try to see if there is more that can
be filled by default.

Thank you for your comments.
---
net/core/devlink.c | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)

diff --git a/net/core/devlink.c b/net/core/devlink.c
index 7f789bbcbbd7..1908b360caf7 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c

@@ -18,6 +18,7 @@

#include <linux/netdevice.h>
#include <linux/spinlock.h>
#include <linux/refcount.h>
+#include <linux/usb.h>
#include <linux/workqueue.h>
#include <linux/u64_stats_sync.h>
#include <linux/timekeeping.h>

@@ -6685,12 +6686,37 @@ int devlink_info_version_running_put_ext(struct devlink_info_req *req,

}
EXPORT_SYMBOL_GPL(devlink_info_version_running_put_ext);

+static int devlink_nl_driver_info_get(struct device_driver *drv,
+				      struct devlink_info_req *req)
+{
+	if (!drv)
+		return 0;
+
+	if (drv->name[0])
+		return devlink_info_driver_name_put(req, drv->name);

+
+	return 0;
+}
+
+static int devlink_nl_usb_info_get(struct usb_device *udev,
+				   struct devlink_info_req *req)
+{
+	if (!udev)
+		return 0;
+
+	if (udev->serial[0])
+		return devlink_info_serial_number_put(req, udev->serial);
+
+	return 0;
+}
+
static int
devlink_nl_info_fill(struct sk_buff *msg, struct devlink *devlink,
		     enum devlink_command cmd, u32 portid,
		     u32 seq, int flags, struct netlink_ext_ack *extack)
{
	struct devlink_info_req req = {};
+	struct device *dev = devlink_to_dev(devlink);
	void *hdr;
	int err;

@@ -6707,6 +6733,16 @@ devlink_nl_info_fill(struct sk_buff *msg, struct devlink *devlink,

	if (err)
		goto err_cancel_msg;

+	err = devlink_nl_driver_info_get(dev->driver, &req);
+	if (err)
+		goto err_cancel_msg;
+
+	if (!strcmp(dev->parent->type->name, "usb_device")) {