Re: [PATCH v2] net: usb: cdc_mbim: add MeiG Smart SRM821 to ZLP whitelist

[Paolo Abeni]

On 9/20/26 09:44, Ming Wang wrote:
> The MeiG Smart SRM821 5G module (0x2dee:0x4d53) crashes and drops off
> the USB bus when it receives a Zero Length Packet (ZLP) after sending
> or receiving an NTB of exactly 16384 bytes (tx_max).
>
> According to the MBIM specification, devices do not require a ZLP
> if the NTB size is exactly dwNtbOutMaxSize. However, the cdc_mbim
> driver defaults to sending ZLPs for devices not explicitly whitelisted
> to accommodate non-conformant hardware. This default behavior breaks
> the strictly conformant MeiG SRM821 module.
>
> Add this device to the ZLP conformance whitelist (cdc_mbim_info) so
> the driver will pad the NTB to avoid sending ZLPs, preventing the
> device firmware from crashing.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Ming Wang <wangming01@xxxxxxxxxxx>

Before any other step, please read:

https://elixir.bootlin.com/linux/v7.3-rc3/source/Documentation/process/maintainer-netdev.rst#L454

AFAICS this is actually support for additional H/W, just worded in
very unusual way: please reword the commit message accordingly and
drop stable from CC.

/P