FAILED: patch "[PATCH] usb: gadget: u_ether: Fix host MAC address case" failed to apply to 5.4-stable tree

The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y
git checkout FETCH_HEAD
git cherry-pick -x 3c0f4f09c063e143822393d99cb2b19a85451c07
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2023052211-lying-sandworm-11db@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

3c0f4f09c063 ("usb: gadget: u_ether: Fix host MAC address case") 938fc6453176 ("usb: gadget: u_ether: Convert prints to device prints") 508aeb54e4f0 ("usb: gadget: u_ether: Remove duplicated include in u_ether.c") 890d5b40908b ("usb: gadget: u_ether: fix race in setting MAC address in setup phase")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 3c0f4f09c063e143822393d99cb2b19a85451c07 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Konrad=20Gr=C3=A4fe?= <[email protected]>
Date: Fri, 5 May 2023 16:36:40 +0200
Subject: [PATCH] usb: gadget: u_ether: Fix host MAC address case
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The CDC-ECM specification [1] requires to send the host MAC address as an uppercase hexadecimal string in chapter "5.4 Ethernet Networking Functional Descriptor":
The Unicode character is chosen from the set of values 30h through 39h and 41h through 46h (0-9 and A-F).

However, snprintf(.., "%pm", ..) generates a lowercase MAC address string. While most host drivers are tolerant to this, UsbNcm.sys on Windows 10 is not. Instead it uses a different MAC address with all bytes set to zero including and after the first byte containing a lowercase letter. On Windows 11 Microsoft fixed it, but apparently they did not backport the fix.

This change fixes the issue by upper-casing the MAC to comply with the specification.

[1]: https://www.usb.org/document-library/class-definitions-communication-devices-12, file ECM120.pdf

index 6956ad8ba8dd..a366abb45623 100644
@@ -17,6 +17,7 @@
 #include <linux/etherdevice.h>
 #include <linux/ethtool.h>
 #include <linux/if_vlan.h>
+#include <linux/string_helpers.h>
 #include <linux/usb/composite.h>
 
 #include "u_ether.h"

@@ -965,6 +966,8 @@ int gether_get_host_addr_cdc(struct net_device *net, char *host_addr, int len)
 	dev = netdev_priv(net);
 	snprintf(host_addr, len, "%pm", dev->host_mac);
 
+	string_upper(host_addr, host_addr);
+
 	return strlen(host_addr);
 }
 EXPORT_SYMBOL_GPL(gether_get_host_addr_cdc);