net: cdc_ncm: workaround for missing CDC Union (9992c2e2) · Commits · 戴 / test

Adding support for the MBIM mode in some Sierra Wireless devices. Some Sierra Wireless firmwares support CDC MBIM but have no CDC Union funtional descriptor. This violates the MBIM specification, but we can easily work around the bug by looking at the Interface Association Descriptor instead. This is most likely what Windows uses too, which explains how the firmware bug has gone unnoticed until now. This change will not affect any currently supported device conforming to the NCM or MBIM specifications, as they must have the CDC Union descriptor. Cc: Greg Suarez <gsuarez@smithmicro.com> Cc: Alexey Orishko <alexey.orishko@stericsson.com> Signed-off-by:

Bjørn Mork <bjorn@mork.no> Signed-off-by:

David S. Miller <davem@davemloft.net>

drivers/net/usb/cdc_ncm.c

+27 −0

Original line number	Diff line number	Diff line
		@@ -344,6 +344,23 @@ static const struct ethtool_ops cdc_ncm_ethtool_ops = {
		.nway_reset = usbnet_nway_reset,
		};

		/* return first slave interface if an IAD matches the given master */
		static struct usb_interface get_iad_slave(struct usb_device udev,
		struct usb_interface *master) {
		int i;
		struct usb_interface_assoc_descriptor *iad;
		u8 mnum = master->cur_altsetting->desc.bInterfaceNumber;

		for (i = 0; i < USB_MAXIADS; i++) {
		iad = udev->actconfig->intf_assoc[i];
		if (!iad)
		break;
		if (iad->bFirstInterface == mnum && iad->bInterfaceCount == 2)
		return usb_ifnum_to_if(udev, mnum + 1);
		}
		return NULL;
		}

		int cdc_ncm_bind_common(struct usbnet dev, struct usb_interface intf, u8 data_altsetting)
		{
		struct cdc_ncm_ctx *ctx;
		@@ -435,6 +452,16 @@ advance:
		len -= temp;
		}

		/* some buggy devices have an IAD but no CDC Union */
		if (!ctx->union_desc) {
		dev_dbg(&intf->dev, "missing CDC Union descriptor\n");
		ctx->data = get_iad_slave(dev->udev, intf);
		if (ctx->data) {
		ctx->control = intf;
		dev_dbg(&intf->dev, "got slave from IAD\n");
		}
		}

		/* check if we got everything */
		if ((ctx->control == NULL) \|\| (ctx->data == NULL) \|\|
		((!ctx->mbim_desc) && ((ctx->ether_desc == NULL) \|\| (ctx->control != intf))))

Admin message