From nobody Thu Sep 24 20:34:28 2026 Received: from mail.loongson.cn (mail.loongson.cn [114.242.206.163]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 91FEC34B662; Sun, 20 Sep 2026 07:29:31 +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=1789889375; cv=none; b=J6QuUZgvBc8MCR7fhzSHGfEf+wwtqxZur3NNw+iqdcx2w3gHi1W9Xe5nWE73BrzkGRiCTTTuow6Cla+AX4i4KmZhy1y8E6rKymj1FAbHTdIgmwK73q99tzE7s/9sXGkONhT4fQBfrpcPgldhDNVuTaBCL354707nKbYkmBM5Whk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789889375; c=relaxed/simple; bh=pBgQ849jDAg8Q305lUVoSgp3uVqS6DnG20M+a5PjCEY=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=oLmnWgeMItHjITooVwvmPp4nvtvXVr6Ztzc1UrUazPTwSRcLAA/CjkGTgMttIRJsLyAR5IGnAgoJub4zvP2HhPEn+oTF9k1pZxxJBFMMVnNnBZDuWqQUA4H65QNUi4FBtw3PNJ113x3qAIwCBziBB1sf54hjeEysBTgD1Fk57sY= 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 _____8Bx79JZi69qW94NAA--.40882S3; Sun, 20 Sep 2026 15:29:29 +0800 (CST) Received: from localhost.localdomain (unknown [10.180.135.190]) by front1 (Coremail) with SMTP id qMiowJAxmM1Xi69qJOsiAA--.7935S2; Sun, 20 Sep 2026 15:29:28 +0800 (CST) From: Ming Wang To: netdev@vger.kernel.org Cc: linux-usb@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] net: usb: cdc_mbim: add MeiG Smart SRM821 to ZLP whitelist Date: Sun, 20 Sep 2026 15:29:26 +0800 Message-ID: <20260920072927.825279-1-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: qMiowJAxmM1Xi69qJOsiAA--.7935S2 X-CM-SenderInfo: 5zdqwzxlqjiio6or00hjvr0hdfq/1tbiAQEQEmqvPvQFMAAAs4 X-Coremail-Antispam: 1Uk129KBj93XoW7WF17ZFyrtw1kKw45XF17XFc_yoW8WrWxpF 4rCFyay39xJry5Gw1rA3WfWFy5Zwn3Cay5KFWI93W5Z3Z0ya4aqFyxJFyUKrykAF45AFnF yasxJ3y7Wa1DGwcCm3ZEXasCq-sJn29KB7ZKAUJUUUUf529EdanIXcx71UUUUU7KY7ZEXa sCq-sGcSsGvfJ3Ic02F40EFcxC0VAKzVAqx4xG6I80ebIjqfuFe4nvWSU5nxnvy29KBjDU 0xBIdaVrnRJUUUPIb4IE77IF4wAFF20E14v26r1j6r4UM7CY07I20VC2zVCF04k26cxKx2 IYs7xG6rWj6s0DM7CIcVAFz4kK6r1Y6r17M28lY4IEw2IIxxk0rwA2F7IY1VAKz4vEj48v e4kI8wA2z4x0Y4vE2Ix0cI8IcVAFwI0_JFI_Gr1l84ACjcxK6xIIjxv20xvEc7CjxVAFwI 0_Gr0_Cr1l84ACjcxK6I8E87Iv67AKxVWxJVW8Jr1l84ACjcxK6I8E87Iv6xkF7I0E14v2 6r4UJVWxJr1ln4kS14v26r126r1DM2vYz4IE04k24VAvwVAKI4IrM2AIxVAIcxkEcVAq07 x20xvEncxIr21l57IF6xkI12xvs2x26I8E6xACxx1l5I8CrVACY4xI64kE6c02F40Ex7xf McIj6xIIjxv20xvE14v26r126r1DMcIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Yz7 v_Jr0_Gr1lF7xvr2IYc2Ij64vIr41lc7CjxVAaw2AFwI0_JF0_Jw1l42xK82IYc2Ij64vI r41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1l4IxYO2xFxVAFwI0_JF0_Jw1lx2IqxVAqx4xG67 AKxVWUJVWUGwC20s026x8GjcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r1q6r43MIIY rxkI7VAKI48JMIIF0xvE2Ix0cI8IcVAFwI0_JFI_Gr1lIxAIcVC0I7IYx2IY6xkF7I0E14 v26r1j6r4UMIIF0xvE42xK8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67AKxVWUJVW8 JwCI42IY6I8E87Iv6xkF7I0E14v26r1j6r4UYxBIdaVFxhVjvjDU0xZFpf9x07jY0PfUUU UU= 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. Signed-off-by: Ming Wang --- drivers/net/usb/cdc_mbim.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/net/usb/cdc_mbim.c b/drivers/net/usb/cdc_mbim.c index 877fb0ed7d3d..bf3e6af7d7c9 100644 --- a/drivers/net/usb/cdc_mbim.c +++ b/drivers/net/usb/cdc_mbim.c @@ -631,6 +631,10 @@ static const struct usb_device_id mbim_devs[] =3D { .driver_info =3D (unsigned long)&cdc_mbim_info, }, /* ZLP conformance whitelist: All Ericsson MBIM devices */ + /* 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, + }, { USB_VENDOR_AND_INTERFACE_INFO(0x0bdb, USB_CLASS_COMM, USB_CDC_SUBCLASS_= MBIM, USB_CDC_PROTO_NONE), .driver_info =3D (unsigned long)&cdc_mbim_info, }, --=20 2.43.7