From nobody Thu Sep 24 20:37:00 2026 Received: from mail.loongson.cn (mail.loongson.cn [114.242.206.163]) by smtp.subspace.kernel.org (Postfix) with ESMTP id E88833E40E4; Sun, 20 Sep 2026 07:45:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=114.242.206.163 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789890308; cv=none; b=qxc6QdE0GjeYcIz6Oxykpuhu3chqWr++eFK5o2zfieP66mJSrMvVA1bumZkeDqmh59mWvZddATJ+hV1GqV2OHv9OJWix5CMREA72TbF9Rc26LN2De2Gyd1mpt1xkO3T941M36ON/P8OK45rKOs/OyoBXQ3JQOl/0fOeTVe0wChQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789890308; c=relaxed/simple; bh=10fE2iWtbvNRkibWkIM5wVpvO5z6pmhPHedJTmBlDIk=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=K9d4VgpF3AJLHZxmE6kQim8wGkl2079y/Zg7ysMR5nV4GFzwexMBT0xnMQkU9zvaVLiG/CAwRTFl3w7MhD7czYdHC5t05w3M6HETZxBdZq1Lb/dNw6cFCWxCrraXWPtXYqMBTR/fQdse0YV9RSSNWowqSVzHr1v751yGxYYyYuE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=loongson.cn; spf=pass smtp.mailfrom=loongson.cn; arc=none smtp.client-ip=114.242.206.163 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=loongson.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=loongson.cn Received: from loongson.cn (unknown [10.180.135.190]) by gateway (Coremail) with SMTP id _____8BxbdL_jq9q6t4NAA--.41250S3; Sun, 20 Sep 2026 15:45:03 +0800 (CST) Received: from localhost.localdomain (unknown [10.180.135.190]) by front1 (Coremail) with SMTP id qMiowJCxPs_9jq9qUOwiAA--.8682S2; Sun, 20 Sep 2026 15:45:02 +0800 (CST) From: Ming Wang To: netdev@vger.kernel.org Cc: linux-usb@vger.kernel.org, stable@vger.kernel.org, Ming Wang , Oliver Neukum , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , linux-kernel@vger.kernel.org Subject: [PATCH v2] net: usb: cdc_mbim: add MeiG Smart SRM821 to ZLP whitelist Date: Sun, 20 Sep 2026 15:44:59 +0800 Message-ID: <20260920074500.826121-1-wangming01@loongson.cn> X-Mailer: git-send-email 2.43.7 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: qMiowJCxPs_9jq9qUOwiAA--.8682S2 X-CM-SenderInfo: 5zdqwzxlqjiio6or00hjvr0hdfq/1tbiAQEQEmqvPvQFYgABsr X-Coremail-Antispam: 1Uk129KBj93XoW7WF17ZFyrtw1kKw45XF17XFc_yoW8WFW3pF 4rCFyYv39xJFW5Kw1rAw48WFyrZwn3Cay5KFWI93WY93Z0ya4aqFyxGFy5K34kGF45AF12 yF93t34xWa1DAwcCm3ZEXasCq-sJn29KB7ZKAUJUUUUx529EdanIXcx71UUUUU7KY7ZEXa sCq-sGcSsGvfJ3Ic02F40EFcxC0VAKzVAqx4xG6I80ebIjqfuFe4nvWSU5nxnvy29KBjDU 0xBIdaVrnRJUUUPSb4IE77IF4wAFF20E14v26r1j6r4UM7CY07I20VC2zVCF04k26cxKx2 IYs7xG6rWj6s0DM7CIcVAFz4kK6r1Y6r17M28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48v e4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_JFI_Gr1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI 0_Jr0_Gr1l84ACjcxK6I8E87Iv67AKxVW8Jr0_Cr1UM28EF7xvwVC2z280aVCY1x0267AK xVW8Jr0_Cr1UM2kKe7AKxVWUAVWUtwAac4AC62xK8xCEY4vEwIxC4wAS0I0E0xvYzxvE52 x082IY62kv0487Mc804VCY07AIYIkI8VC2zVCFFI0UMc02F40EFcxC0VAKzVAqx4xG6I80 ewAv7VC0I7IYx2IY67AKxVWUAVWUtwAv7VC2z280aVAFwI0_Gr0_Cr1lOx8S6xCaFVCjc4 AY6r1j6r4UM4x0Y48IcxkI7VAKI48JMxkF7I0En4kS14v26r126r1DMxAIw28IcxkI7VAK I48JMxC20s026xCaFVCjc4AY6r1j6r4UMxCIbckI1I0E14v26r126r1DMI8I3I0E5I8CrV AFwI0_Jr0_Jr4lx2IqxVCjr7xvwVAFwI0_JrI_JrWlx4CE17CEb7AF67AKxVWUtVW8ZwCI c40Y0x0EwIxGrwCI42IY6xIIjxv20xvE14v26r1I6r4UMIIF0xvE2Ix0cI8IcVCY1x0267 AKxVWUJVW8JwCI42IY6xAIw20EY4v20xvaj40_Jr0_JF4lIxAIcVC2z280aVAFwI0_Gr0_ Cr1lIxAIcVC2z280aVCY1x0267AKxVW8JVW8JrUvcSsGvfC2KfnxnUUI43ZEXa7IU8N_-P UUUUU== Content-Type: text/plain; charset="utf-8" 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 --- v2: moved MeiG entry below Ericsson for better grouping; added Cc stable drivers/net/usb/cdc_mbim.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/net/usb/cdc_mbim.c b/drivers/net/usb/cdc_mbim.c index 877fb0ed7d3d..a7010a0664c7 100644 --- a/drivers/net/usb/cdc_mbim.c +++ b/drivers/net/usb/cdc_mbim.c @@ -635,6 +635,11 @@ static const struct usb_device_id mbim_devs[] =3D { .driver_info =3D (unsigned long)&cdc_mbim_info, }, =20 + /* MeiG Smart SRM821 ZLP conformance */ + { USB_DEVICE_AND_INTERFACE_INFO(0x2dee, 0x4d53, USB_CLASS_COMM, USB_CDC_S= UBCLASS_MBIM, USB_CDC_PROTO_NONE), + .driver_info =3D (unsigned long)&cdc_mbim_info, + }, + /* Some Huawei devices, ME906s-158 (12d1:15c1) and E3372 * (12d1:157d), are known to fail unless the NDP is placed * after the IP packets. Applying the quirk to all Huawei --=20 2.43.7