net: usb: cdc_mbim: add MeiG Smart SRM821 to ZLP whitelist

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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@vger.kernel.org
Signed-off-by: Ming Wang <wangming01@loongson.cn>
Link: https://patch.msgid.link/20260920074500.826121-1-wangming01@loongson.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

...

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Ming Wang 2026-09-20 15:44:59 +08:00 • committed by Jakub Kicinski

parent fe99bbeee5

commit f75f21ef36

1 changed files with 5 additions and 0 deletions

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drivers/net/usb/cdc_mbim.c

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