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

[Greg KH]

On Thu, Sep 24, 2026 at 12:24:06PM +0200, Paolo Abeni wrote:
> 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.

Why drop stable from cc:?  Do you not want it in any stable kernel
release?  Seems like it should be to me, we gladly take quirk additions
and new device ids in stable kernels.

thanks,

greg k-h