[PATCH net-next v4 0/2] adjust MTU as indicated by MBIM extended functional descriptor

[PATCH net-next v4 0/2] adjust MTU as indicated by MBIM extended functional descriptor

[Ben Chan]

The MBIM extended functional descriptor, defined in "Universal Serial Bus
Communications Class Subclass Specification for Mobile Broadband Interface
Model, Revision 1.0, Errata-1" by USB-IF, indicates the operator preferred MTU
value via a wMTU field.

This patch set ensures that the initial MTU value set by cdc_ncm on a MBIM net
device does not exceed the wMTU value, provided the MBIM device exposes a MBIM
extended functional descriptor.

* Changelog
v2: Fixed a le16_to_cpu conversion issue in patch 2/2 pointed out by
    Bjørn Mork <bjorn@mork.no>
v3: No code changes. Resubmitted to include patch 1/2 as suggested by
    David Miller <davem@davemloft.net>
v4: No code changes. Resubmitted as suggested by David Miller:
    - Added a summary of the patch set
    - Carried the ACK from Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    - Added a specified the tree (net-next) to apply the patch set to

Ben Chan (2):
  USB: cdc: add MBIM extended functional descriptor structure
  net: cdc_ncm: respect operator preferred MTU reported by MBIM

 drivers/net/usb/cdc_ncm.c    | 17 +++++++++++++++++
 include/linux/usb/cdc_ncm.h  |  1 +
 include/uapi/linux/usb/cdc.h | 12 ++++++++++++
 3 files changed, 30 insertions(+)

-- 
1.9.0.279.gdc9e3eb

[PATCH net-next v4 1/2] USB: cdc: add MBIM extended functional descriptor structure

[Ben Chan]

This patch adds the MBIM extended functional descriptor structure
defined in "Universal Serial Bus Communications Class Subclass
Specification for Mobile Broadband Interface Model, Revision 1.0,
Errata-1" published by USB-IF.

Signed-off-by: Ben Chan <benchan@chromium.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/uapi/linux/usb/cdc.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/include/uapi/linux/usb/cdc.h b/include/uapi/linux/usb/cdc.h
index f35aa0a..b6a9cdd 100644
--- a/include/uapi/linux/usb/cdc.h
+++ b/include/uapi/linux/usb/cdc.h
@@ -56,6 +56,7 @@
 #define USB_CDC_OBEX_TYPE		0x15
 #define USB_CDC_NCM_TYPE		0x1a
 #define USB_CDC_MBIM_TYPE		0x1b
+#define USB_CDC_MBIM_EXTENDED_TYPE	0x1c
 
 /* "Header Functional Descriptor" from CDC spec  5.2.3.1 */
 struct usb_cdc_header_desc {
@@ -205,6 +206,17 @@ struct usb_cdc_mbim_desc {
 	__u8    bmNetworkCapabilities;
 } __attribute__ ((packed));
 
+/* "MBIM Extended Functional Descriptor" from CDC MBIM spec 1.0 errata-1 */
+struct usb_cdc_mbim_extended_desc {
+	__u8	bLength;
+	__u8	bDescriptorType;
+	__u8	bDescriptorSubType;
+
+	__le16	bcdMBIMExtendedVersion;
+	__u8	bMaxOutstandingCommandMessages;
+	__le16	wMTU;
+} __attribute__ ((packed));
+
 /*-------------------------------------------------------------------------*/
 
 /*
-- 
1.9.0.279.gdc9e3eb

[PATCH net-next v4 2/2] net: cdc_ncm: respect operator preferred MTU reported by MBIM

[Ben Chan]

According to "Universal Serial Bus Communications Class Subclass
Specification for Mobile Broadband Interface Model, Revision 1.0,
Errata-1" published by USB-IF, the wMTU field of the MBIM extended
functional descriptor indicates the operator preferred MTU for IP data
streams.

This patch modifies cdc_ncm_setup to ensure that the MTU value set on
the usbnet device does not exceed the operator preferred MTU indicated
by wMTU if the MBIM device exposes a MBIM extended functional
descriptor.

Signed-off-by: Ben Chan <benchan@chromium.org>
---
 drivers/net/usb/cdc_ncm.c   | 17 +++++++++++++++++
 include/linux/usb/cdc_ncm.h |  1 +
 2 files changed, 18 insertions(+)

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index dbff290..e8711a8 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -74,6 +74,7 @@ static int cdc_ncm_setup(struct usbnet *dev)
 	u8 iface_no;
 	int err;
 	int eth_hlen;
+	u16 mbim_mtu;
 	u16 ntb_fmt_supported;
 	__le16 max_datagram_size;
 
@@ -261,6 +262,14 @@ out:
 	/* set MTU to max supported by the device if necessary */
 	if (dev->net->mtu > ctx->max_datagram_size - eth_hlen)
 		dev->net->mtu = ctx->max_datagram_size - eth_hlen;
+
+	/* do not exceed operater preferred MTU */
+	if (ctx->mbim_extended_desc) {
+		mbim_mtu = le16_to_cpu(ctx->mbim_extended_desc->wMTU);
+		if (mbim_mtu != 0 && mbim_mtu < dev->net->mtu)
+			dev->net->mtu = mbim_mtu;
+	}
+
 	return 0;
 }
 
@@ -399,6 +408,14 @@ int cdc_ncm_bind_common(struct usbnet *dev, struct usb_interface *intf, u8 data_
 			ctx->mbim_desc = (const struct usb_cdc_mbim_desc *)buf;
 			break;
 
+		case USB_CDC_MBIM_EXTENDED_TYPE:
+			if (buf[0] < sizeof(*(ctx->mbim_extended_desc)))
+				break;
+
+			ctx->mbim_extended_desc =
+				(const struct usb_cdc_mbim_extended_desc *)buf;
+			break;
+
 		default:
 			break;
 		}
diff --git a/include/linux/usb/cdc_ncm.h b/include/linux/usb/cdc_ncm.h
index c3fa807..bdf05fb 100644
--- a/include/linux/usb/cdc_ncm.h
+++ b/include/linux/usb/cdc_ncm.h
@@ -93,6 +93,7 @@ struct cdc_ncm_ctx {
 
 	const struct usb_cdc_ncm_desc *func_desc;
 	const struct usb_cdc_mbim_desc *mbim_desc;
+	const struct usb_cdc_mbim_extended_desc *mbim_extended_desc;
 	const struct usb_cdc_ether_desc *ether_desc;
 
 	struct usb_interface *control;
-- 
1.9.0.279.gdc9e3eb

Re: [PATCH net-next v4 0/2] adjust MTU as indicated by MBIM extended functional descriptor

[David Miller]

From: Ben Chan <benchan@chromium.org>
Date: Wed, 19 Mar 2014 14:00:04 -0700

> The MBIM extended functional descriptor, defined in "Universal Serial Bus
> Communications Class Subclass Specification for Mobile Broadband Interface
> Model, Revision 1.0, Errata-1" by USB-IF, indicates the operator preferred MTU
> value via a wMTU field.
> 
> This patch set ensures that the initial MTU value set by cdc_ncm on a MBIM net
> device does not exceed the wMTU value, provided the MBIM device exposes a MBIM
> extended functional descriptor.
> 
> * Changelog
> v2: Fixed a le16_to_cpu conversion issue in patch 2/2 pointed out by
>     Bjørn Mork <bjorn@mork.no>
> v3: No code changes. Resubmitted to include patch 1/2 as suggested by
>     David Miller <davem@davemloft.net>
> v4: No code changes. Resubmitted as suggested by David Miller:
>     - Added a summary of the patch set
>     - Carried the ACK from Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>     - Added a specified the tree (net-next) to apply the patch set to

Series applied to net-next, thanks Ben.