[PATCH v2 09/16] HID: Include firmware version in the uevent

["Derek J. Clark" <derekjohn.clark@gmail.com>]

From: Mario Limonciello <mario.limonciello@amd.com>

Userspace software fwupd probes some HID devices when the daemon starts
up to determine the current firmware version in order to be able to offer
updated firmware if the manufacturer has made it available.

In order to do this fwupd will detach the existing kernel driver if one
is present, send a HID command and then reattach the kernel driver.

This can be problematic if the user is using the HID device at the time
that fwupd probes the hardware and can cause a few frames of input to be
dropped.  In some cases HID drivers already have a command to look up the
firmware version, and so if that is exported to userspace fwupd can discover
it and avoid needing to detach the kernel driver until it's time to update
the device.

Introduce a new member in the struct hid_device for the version and export
a new uevent variable HID_FIRMWARE_VERSION that will display the version
that HID drivers obtained.

Cc: Richard Hughes <hughsient@gmail.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/hid/hid-core.c | 5 +++++
 include/linux/hid.h    | 1 +
 2 files changed, 6 insertions(+)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index a5b3a8ca2fcb..524f2b9ed512 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -2887,6 +2887,11 @@ static int hid_uevent(const struct device *dev, struct kobj_uevent_env *env)
 	if (add_uevent_var(env, "MODALIAS=hid:b%04Xg%04Xv%08Xp%08X",
 			   hdev->bus, hdev->group, hdev->vendor, hdev->product))
 		return -ENOMEM;
+	if (hdev->firmware_version) {
+		if (add_uevent_var(env, "HID_FIRMWARE_VERSION=0x%04llX",
+				   hdev->firmware_version))
+			return -ENOMEM;
+	}
 
 	return 0;
 }
diff --git a/include/linux/hid.h b/include/linux/hid.h
index a4ddb94e3ee5..8249da55c9ba 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -698,6 +698,7 @@ struct hid_device {
 	char name[128];							/* Device name */
 	char phys[64];							/* Device physical location */
 	char uniq[64];							/* Device unique identifier (serial #) */
+	u64 firmware_version;						/* Firmware version */
 
 	void *driver_data;
 
-- 
2.51.2