From: Paolo Abeni <pabeni@redhat.com>
To: Ming Wang <wangming01@loongson.cn>, netdev@vger.kernel.org
Cc: linux-usb@vger.kernel.org, stable@vger.kernel.org,
Oliver Neukum <oliver@neukum.org>,
Andrew Lunn <andrew+netdev@lunn.ch>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] net: usb: cdc_mbim: add MeiG Smart SRM821 to ZLP whitelist
Date: Thu, 24 Sep 2026 12:24:06 +0200 [thread overview]
Message-ID: <4d5e2857-e6eb-43e2-b668-83e779aaa734@redhat.com> (raw)
In-Reply-To: <20260920074500.826121-1-wangming01@loongson.cn>
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@vger.kernel.org
> Signed-off-by: Ming Wang <wangming01@loongson.cn>
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
next prev parent reply other threads:[~2026-09-24 10:24 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-20 7:44 [PATCH v2] net: usb: cdc_mbim: add MeiG Smart SRM821 to ZLP whitelist Ming Wang
2026-09-24 10:24 ` Paolo Abeni [this message]
2026-09-24 14:22 ` Greg KH
2026-09-24 16:28 ` Jakub Kicinski
2026-09-25 5:12 ` Greg KH
2026-09-25 20:23 ` Jakub Kicinski
2026-09-24 16:30 ` patchwork-bot+netdevbpf
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