Re: [PATCH v3] net/can/gs_usb: increase max interface to U8_MAX

[Vincent Mailhol]

On 9/30/25 12:06 PM, Celeste Liu wrote:
> This issue was found by Runcheng Lu when develop HSCanT USB to CAN FD
> converter[1]. The original developers may have only 3 intefaces device to
                                                        ^^^^^^^^^
interfaces (missing "r")

> test so they write 3 here and wait for future change.
> 
> During the HSCanT development, we actually used 4 interfaces, so the
> limitation of 3 is not enough now. But just increase one is not
> future-proofed. Since the channel type in gs_host_frame is u8, just
> increase interface number limit to max size of u8 safely.
> 
> [1]: https://github.com/cherry-embedded/HSCanT-hardware
> 
> Fixes: d08e973a77d1 ("can: gs_usb: Added support for the GS_USB CAN devices")
> Reported-by: Runcheng Lu <runcheng.lu@xxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Celeste Liu <uwu@xxxxxxxxxxxxxxxxx>

Reviewed-by: Vincent Mailhol <mailhol@xxxxxxxxxx>

The patch is good as-is. However, speaking of the interface numbers, there is
another issue in this gs_usb driver: net_device->dev_port is not populated, and
according to the documentation, this is a bug.


See the description here:



  https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-class-net



  What:		/sys/class/net/<iface>/dev_port

  Date:		February 2014

  KernelVersion:	3.15

  Contact:	netdev@xxxxxxxxxxxxxxx

  Description:

  		Indicates the port number of this network device, formatted

  		as a decimal value. Some NICs have multiple independent ports

  		on the same PCI bus, device and function. This attribute allows

  		userspace to distinguish the respective interfaces.



  		Note: some device drivers started to use 'dev_id' for this

  		purpose since long before 3.15 and have not adopted the new

  		attribute ever since. To query the port number, some tools look

  		exclusively at 'dev_port', while others only consult 'dev_id'.

  		If a network device has multiple client adapter ports as

  		described in the previous paragraph and does not set this

  		attribute to its port number, it's a kernel bug.



Would you mind sending a separate patch (with a Fixes: tag) to resolve this?


Yours sincerely,
Vincent Mailhol