CDC: common parser for extra headers

CDC drivers all implement their own parser for the extra headers.
This patch fixes the code duplication introducing a single common
parser in usbnet.

Signed-off-by: Oliver Neukum <oneukum@suse.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/usbnet.c

@@ -42,6 +42,7 @@
 #include <linux/mii.h>
 #include <linux/usb.h>
 #include <linux/usb/usbnet.h>
+#include <linux/usb/cdc.h>
 #include <linux/slab.h>
 #include <linux/kernel.h>
 #include <linux/pm_runtime.h>
@@ -1962,6 +1963,143 @@ out:
 	return err;
 }
 
+int cdc_parse_cdc_header(struct usb_cdc_parsed_header *hdr,
+				struct usb_interface *intf,
+				u8 *buffer,
+				int buflen)
+{
+	/* duplicates are ignored */
+	struct usb_cdc_union_desc *union_header = NULL;
+
+	/* duplicates are not tolerated */
+	struct usb_cdc_header_desc *header = NULL;
+	struct usb_cdc_ether_desc *ether = NULL;
+	struct usb_cdc_mdlm_detail_desc *detail = NULL;
+	struct usb_cdc_mdlm_desc *desc = NULL;
+
+	unsigned int elength;
+	int cnt = 0;
+
+	memset(hdr, 0x00, sizeof(struct usb_cdc_parsed_header));
+	hdr->phonet_magic_present = false;
+	while (buflen > 0) {
+		elength = buffer[0];
+		if (!elength) {
+			dev_err(&intf->dev, "skipping garbage byte\n");
+			elength = 1;
+			goto next_desc;
+		}
+		if (buffer[1] != USB_DT_CS_INTERFACE) {
+			dev_err(&intf->dev, "skipping garbage\n");
+			goto next_desc;
+		}
+
+		switch (buffer[2]) {
+		case USB_CDC_UNION_TYPE: /* we've found it */
+			if (elength < sizeof(struct usb_cdc_union_desc))
+				goto next_desc;
+			if (union_header) {
+				dev_err(&intf->dev, "More than one union descriptor, skipping ...\n");
+				goto next_desc;
+			}
+			union_header = (struct usb_cdc_union_desc *)buffer;
+			break;
+		case USB_CDC_COUNTRY_TYPE:
+			if (elength < sizeof(struct usb_cdc_country_functional_desc))
+				goto next_desc;
+			hdr->usb_cdc_country_functional_desc =
+				(struct usb_cdc_country_functional_desc *)buffer;
+			break;
+		case USB_CDC_HEADER_TYPE:
+			if (elength != sizeof(struct usb_cdc_header_desc))
+				goto next_desc;
+			if (header)
+				return -EINVAL;
+			header = (struct usb_cdc_header_desc *)buffer;
+			break;
+		case USB_CDC_ACM_TYPE:
+			if (elength < sizeof(struct usb_cdc_acm_descriptor))
+				goto next_desc;
+			hdr->usb_cdc_acm_descriptor =
+				(struct usb_cdc_acm_descriptor *)buffer;
+			break;
+		case USB_CDC_ETHERNET_TYPE:
+			if (elength != sizeof(struct usb_cdc_ether_desc))
+				goto next_desc;
+			if (ether)
+				return -EINVAL;
+			ether = (struct usb_cdc_ether_desc *)buffer;
+			break;
+		case USB_CDC_CALL_MANAGEMENT_TYPE:
+			if (elength < sizeof(struct usb_cdc_call_mgmt_descriptor))
+				goto next_desc;
+			hdr->usb_cdc_call_mgmt_descriptor =
+				(struct usb_cdc_call_mgmt_descriptor *)buffer;
+			break;
+		case USB_CDC_DMM_TYPE:
+			if (elength < sizeof(struct usb_cdc_dmm_desc))
+				goto next_desc;
+			hdr->usb_cdc_dmm_desc =
+				(struct usb_cdc_dmm_desc *)buffer;
+			break;
+		case USB_CDC_MDLM_TYPE:
+			if (elength < sizeof(struct usb_cdc_mdlm_desc *))
+				goto next_desc;
+			if (desc)
+				return -EINVAL;
+			desc = (struct usb_cdc_mdlm_desc *)buffer;
+			break;
+		case USB_CDC_MDLM_DETAIL_TYPE:
+			if (elength < sizeof(struct usb_cdc_mdlm_detail_desc *))
+				goto next_desc;
+			if (detail)
+				return -EINVAL;
+			detail = (struct usb_cdc_mdlm_detail_desc *)buffer;
+			break;
+		case USB_CDC_NCM_TYPE:
+			if (elength < sizeof(struct usb_cdc_ncm_desc))
+				goto next_desc;
+			hdr->usb_cdc_ncm_desc = (struct usb_cdc_ncm_desc *)buffer;
+			break;
+		case USB_CDC_MBIM_TYPE:
+			if (elength < sizeof(struct usb_cdc_mbim_desc))
+				goto next_desc;
+
+			hdr->usb_cdc_mbim_desc = (struct usb_cdc_mbim_desc *)buffer;
+			break;
+		case USB_CDC_MBIM_EXTENDED_TYPE:
+			if (elength < sizeof(struct usb_cdc_mbim_extended_desc))
+				break;
+			hdr->usb_cdc_mbim_extended_desc =
+				(struct usb_cdc_mbim_extended_desc *)buffer;
+			break;
+		case CDC_PHONET_MAGIC_NUMBER:
+			hdr->phonet_magic_present = true;
+			break;
+		default:
+			/*
+			 * there are LOTS more CDC descriptors that
+			 * could legitimately be found here.
+			 */
+			dev_dbg(&intf->dev, "Ignoring descriptor: type %02x, length %ud\n",
+					buffer[2], elength);
+			goto next_desc;
+		}
+		cnt++;
+next_desc:
+		buflen -= elength;
+		buffer += elength;
+	}
+	hdr->usb_cdc_union_desc = union_header;
+	hdr->usb_cdc_header_desc = header;
+	hdr->usb_cdc_mdlm_detail_desc = detail;
+	hdr->usb_cdc_mdlm_desc = desc;
+	hdr->usb_cdc_ether_desc = ether;
+	return cnt;
+}
+
+EXPORT_SYMBOL(cdc_parse_cdc_header);
+
 /*
  * The function can't be called inside suspend/resume callback,
  * otherwise deadlock will be caused.

include/linux/usb/cdc.h

@@ -0,0 +1,47 @@
+/*
+ * USB CDC common helpers
+ *
+ * Copyright (c) 2015 Oliver Neukum <oneukum@suse.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ */
+
+#include <uapi/linux/usb/cdc.h>
+
+/*
+ * inofficial magic numbers
+ */
+
+#define CDC_PHONET_MAGIC_NUMBER		0xAB
+
+/*
+ * parsing CDC headers
+ */
+
+struct usb_cdc_parsed_header {
+	struct usb_cdc_union_desc *usb_cdc_union_desc;
+	struct usb_cdc_header_desc *usb_cdc_header_desc;
+
+	struct usb_cdc_call_mgmt_descriptor *usb_cdc_call_mgmt_descriptor;
+	struct usb_cdc_acm_descriptor *usb_cdc_acm_descriptor;
+	struct usb_cdc_country_functional_desc *usb_cdc_country_functional_desc;
+	struct usb_cdc_network_terminal_desc *usb_cdc_network_terminal_desc;
+	struct usb_cdc_ether_desc *usb_cdc_ether_desc;
+	struct usb_cdc_dmm_desc *usb_cdc_dmm_desc;
+	struct usb_cdc_mdlm_desc *usb_cdc_mdlm_desc;
+	struct usb_cdc_mdlm_detail_desc *usb_cdc_mdlm_detail_desc;
+	struct usb_cdc_obex_desc *usb_cdc_obex_desc;
+	struct usb_cdc_ncm_desc *usb_cdc_ncm_desc;
+	struct usb_cdc_mbim_desc *usb_cdc_mbim_desc;
+	struct usb_cdc_mbim_extended_desc *usb_cdc_mbim_extended_desc;
+
+	bool phonet_magic_present;
+};
+
+
+int cdc_parse_cdc_header(struct usb_cdc_parsed_header *hdr,
+				struct usb_interface *intf,
+				u8 *buffer,
+				int buflen);