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

[Mattijs Korpershoek]

Hi Marek,

Thank you for the patch.

On Sat, Jun 13, 2026 at 04:54, Marek Vasut <marex at 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 at nabladev.com>

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

> ---