| Message ID | 20230428064905.145858-2-k.graefe@gateware.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v4,1/2] vsprintf: Add %p[mM]U for uppercase MAC address | expand |
diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c index 6956ad8ba8dd..70e6b825654c 100644 --- a/drivers/usb/gadget/function/u_ether.c +++ b/drivers/usb/gadget/function/u_ether.c @@ -963,7 +963,7 @@ int gether_get_host_addr_cdc(struct net_device *net, char *host_addr, int len) return -EINVAL; dev = netdev_priv(net); - snprintf(host_addr, len, "%pm", dev->host_mac); + snprintf(host_addr, len, "%pmU", dev->host_mac); return strlen(host_addr); }
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 using "%pmU" to generate an uppercase hex string to comply with the specification. [1]: https://www.usb.org/document-library/class-definitions-communication-devices-12, file ECM120.pdf Fixes: bcd4a1c40bee ("usb: gadget: u_ether: construct with default values and add setters/getters") Cc: stable@vger.kernel.org Signed-off-by: Konrad Gräfe <k.graefe@gateware.de> --- Changes since v3: None Changes since v2: * Add uppercase MAC address format string and use that instead of manually uppercasing the resulting MAC address string. Changes since v1: * Fixed checkpatch.pl warnings drivers/usb/gadget/function/u_ether.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)