[PATCH v2] cmd: ums: Set Device Descriptor iSerial based on serial# env variable

[PATCH v2] cmd: ums: Set Device Descriptor iSerial based on serial# env variable

[Marek Vasut]

The DFU code currently sets the content of "serial#" environment
variable into Device Descriptor iSerial field. This is useful when
there are multiple devices connected to the same host PC and they
have to be told apart. Replicate the same behavior in the UMS code.

Example without serial# set, which is the original behavior:
"
u-boot=> ums 0 mmc 1
UMS: LUN 0, dev mmc 1, hwpart 0, sector 0x0, count 0x1d5a000

$ dmesg -w
...
usb 5-2.3.7: New USB device found, idVendor=0525, idProduct=a4a5, bcdDevice=7e.a7
usb 5-2.3.7: New USB device strings: Mfr=1, Product=2, SerialNumber=0
usb 5-2.3.7: Product: USB download gadget
usb 5-2.3.7: Manufacturer: Vendor
                            <------------------------------- NOT HERE
usb-storage 5-2.3.7:1.0: USB Mass Storage device detected
...

$ lsusb -vd 0525:a4a5

Bus 005 Device 051: ID 0525:a4a5 Netchip Technology, Inc. Linux-USB File-backed Storage Gadget
Negotiated speed: High Speed (480Mbps)
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass            0 [unknown]
  bDeviceSubClass         0 [unknown]
  bDeviceProtocol         0
  bMaxPacketSize0        64
  idVendor           0x0525 Netchip Technology, Inc.
  idProduct          0xa4a5 Linux-USB File-backed Storage Gadget
  bcdDevice           7e.a7
  iManufacturer           1 Vendor
  iProduct                2 USB download gadget
  iSerial                 0 <------------------------------- NOT HERE
...
"

Example with serial# set to 1234abcd, which is the optional new behavior:
"
u-boot=> setenv serial# 1234abcd <------------------------------ HERE
u-boot=> ums 0 mmc 1
UMS: LUN 0, dev mmc 1, hwpart 0, sector 0x0, count 0x1d5a000

$ dmesg -w
...
usb 5-2.3.7: New USB device found, idVendor=0525, idProduct=a4a5, bcdDevice=7e.a7
usb 5-2.3.7: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 5-2.3.7: Product: USB download gadget
usb 5-2.3.7: Manufacturer: Vendor
usb 5-2.3.7: SerialNumber: 1234abcd <--------------------------- HERE
usb-storage 5-2.3.7:1.0: USB Mass Storage device detected
...

$ lsusb -vd 0525:a4a5

Bus 005 Device 052: ID 0525:a4a5 Netchip Technology, Inc. Linux-USB File-backed Storage Gadget
Negotiated speed: High Speed (480Mbps)
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass            0 [unknown]
  bDeviceSubClass         0 [unknown]
  bDeviceProtocol         0
  bMaxPacketSize0        64
  idVendor           0x0525 Netchip Technology, Inc.
  idProduct          0xa4a5 Linux-USB File-backed Storage Gadget
  bcdDevice           7e.a7
  iManufacturer           1 Vendor
  iProduct                2 USB download gadget
  iSerial                 3 1234abcd <-------------------------- HERE
...
"

Signed-off-by: Marek Vasut <marex@nabladev.com>
---
Cc: Lukasz Majewski <lukma@nabladev.com>
Cc: Mattijs Korpershoek <mkorpershoek@kernel.org>
Cc: Simon Glass <sjg@chromium.org>
Cc: Tom Rini <trini@konsulko.com>
Cc: u-boot@lists.denx.de
---
V2: Move to fsg_bind()
---
 drivers/usb/gadget/f_mass_storage.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/usb/gadget/f_mass_storage.c b/drivers/usb/gadget/f_mass_storage.c
index 71dc58da3f0..f82acd10b45 100644
--- a/drivers/usb/gadget/f_mass_storage.c
+++ b/drivers/usb/gadget/f_mass_storage.c
@@ -241,6 +241,7 @@
 
 #include <config.h>
 #include <div64.h>
+#include <env.h>
 #include <hexdump.h>
 #include <log.h>
 #include <malloc.h>
@@ -2651,8 +2652,15 @@ static int fsg_bind(struct usb_configuration *c, struct usb_function *f)
 	struct usb_gadget	*gadget = c->cdev->gadget;
 	int			i;
 	struct usb_ep		*ep;
+	char __maybe_unused	*sn;
 	fsg->gadget = gadget;
 
+	if (CONFIG_IS_ENABLED(ENV_SUPPORT)) {
+		sn = env_get("serial#");
+		if (sn)
+			g_dnl_set_serialnumber(sn);
+	}
+
 	/* New interface */
 	i = usb_interface_id(c, f);
 	if (i < 0)
-- 
2.53.0

Re: [PATCH v2] cmd: ums: Set Device Descriptor iSerial based on serial# env variable

[Mattijs Korpershoek]

Hi Marek,

Thank you for the patch.

On Fri, Jun 26, 2026 at 16:28, Marek Vasut <marex@nabladev.com> wrote:

> The DFU code currently sets the content of "serial#" environment
> variable into Device Descriptor iSerial field. This is useful when
> there are multiple devices connected to the same host PC and they
> have to be told apart. Replicate the same behavior in the UMS code.
>
> Example without serial# set, which is the original behavior:
> "
> u-boot=> ums 0 mmc 1
> UMS: LUN 0, dev mmc 1, hwpart 0, sector 0x0, count 0x1d5a000
>
> $ dmesg -w
> ...
> usb 5-2.3.7: New USB device found, idVendor=0525, idProduct=a4a5, bcdDevice=7e.a7
> usb 5-2.3.7: New USB device strings: Mfr=1, Product=2, SerialNumber=0
> usb 5-2.3.7: Product: USB download gadget
> usb 5-2.3.7: Manufacturer: Vendor
>                             <------------------------------- NOT HERE
> usb-storage 5-2.3.7:1.0: USB Mass Storage device detected
> ...
>
> $ lsusb -vd 0525:a4a5
>
> Bus 005 Device 051: ID 0525:a4a5 Netchip Technology, Inc. Linux-USB File-backed Storage Gadget
> Negotiated speed: High Speed (480Mbps)
> Device Descriptor:
>   bLength                18
>   bDescriptorType         1
>   bcdUSB               2.00
>   bDeviceClass            0 [unknown]
>   bDeviceSubClass         0 [unknown]
>   bDeviceProtocol         0
>   bMaxPacketSize0        64
>   idVendor           0x0525 Netchip Technology, Inc.
>   idProduct          0xa4a5 Linux-USB File-backed Storage Gadget
>   bcdDevice           7e.a7
>   iManufacturer           1 Vendor
>   iProduct                2 USB download gadget
>   iSerial                 0 <------------------------------- NOT HERE
> ...
> "
>
> Example with serial# set to 1234abcd, which is the optional new behavior:
> "
> u-boot=> setenv serial# 1234abcd <------------------------------ HERE
> u-boot=> ums 0 mmc 1
> UMS: LUN 0, dev mmc 1, hwpart 0, sector 0x0, count 0x1d5a000
>
> $ dmesg -w
> ...
> usb 5-2.3.7: New USB device found, idVendor=0525, idProduct=a4a5, bcdDevice=7e.a7
> usb 5-2.3.7: New USB device strings: Mfr=1, Product=2, SerialNumber=3
> usb 5-2.3.7: Product: USB download gadget
> usb 5-2.3.7: Manufacturer: Vendor
> usb 5-2.3.7: SerialNumber: 1234abcd <--------------------------- HERE
> usb-storage 5-2.3.7:1.0: USB Mass Storage device detected
> ...
>
> $ lsusb -vd 0525:a4a5
>
> Bus 005 Device 052: ID 0525:a4a5 Netchip Technology, Inc. Linux-USB File-backed Storage Gadget
> Negotiated speed: High Speed (480Mbps)
> Device Descriptor:
>   bLength                18
>   bDescriptorType         1
>   bcdUSB               2.00
>   bDeviceClass            0 [unknown]
>   bDeviceSubClass         0 [unknown]
>   bDeviceProtocol         0
>   bMaxPacketSize0        64
>   idVendor           0x0525 Netchip Technology, Inc.
>   idProduct          0xa4a5 Linux-USB File-backed Storage Gadget
>   bcdDevice           7e.a7
>   iManufacturer           1 Vendor
>   iProduct                2 USB download gadget
>   iSerial                 3 1234abcd <-------------------------- HERE
> ...
> "
>
> Signed-off-by: Marek Vasut <marex@nabladev.com>

I looked at the linux implementation and I could not find anything
related to the serial number in
drivers/usb/gadget/function/f_mass_storage.c.
I think in linux it's handled by drivers/usb/gadget/configfs.c,
therefore we can't just do a straight port from linux.

This looks good to me.

Reviewed-by: Mattijs Korpershoek <mkorpershoek@kernel.org>