usb: gadget: f_fs: Add support for CCID descriptors.

Nothing to remap, only check length.
Define a minimal structure for CCID descriptor only used to check length.
As this descriptor shares the same value as HID descriptors, keep track and
compare current interface's class to expected HID and CCID standard values.
Signed-off-by: Vincent Pelletier <plr.vincent@gmail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/gadget/function/f_fs.c

@@ -23,6 +23,7 @@
 #include <linux/uio.h>
 #include <asm/unaligned.h>
 
+#include <linux/usb/ccid.h>
 #include <linux/usb/composite.h>
 #include <linux/usb/functionfs.h>
 
@@ -1926,7 +1927,7 @@ typedef int (*ffs_os_desc_callback)(enum ffs_os_desc_type entity,
 
 static int __must_check ffs_do_single_desc(char *data, unsigned len,
 					   ffs_entity_callback entity,
-					   void *priv)
+					   void *priv, int *current_class)
 {
 	struct usb_descriptor_header *_ds = (void *)data;
 	u8 length;
@@ -1984,6 +1985,7 @@ static int __must_check ffs_do_single_desc(char *data, unsigned len,
 		__entity(INTERFACE, ds->bInterfaceNumber);
 		if (ds->iInterface)
 			__entity(STRING, ds->iInterface);
+		*current_class = ds->bInterfaceClass;
 	}
 		break;
 
@@ -1997,11 +1999,22 @@ static int __must_check ffs_do_single_desc(char *data, unsigned len,
 	}
 		break;
 
-	case HID_DT_HID:
-		pr_vdebug("hid descriptor\n");
-		if (length != sizeof(struct hid_descriptor))
-			goto inv_length;
-		break;
+	case USB_TYPE_CLASS | 0x01:
+                if (*current_class == USB_INTERFACE_CLASS_HID) {
+			pr_vdebug("hid descriptor\n");
+			if (length != sizeof(struct hid_descriptor))
+				goto inv_length;
+			break;
+		} else if (*current_class == USB_INTERFACE_CLASS_CCID) {
+			pr_vdebug("ccid descriptor\n");
+			if (length != sizeof(struct ccid_descriptor))
+				goto inv_length;
+			break;
+		} else {
+			pr_vdebug("unknown descriptor: %d for class %d\n",
+			      _ds->bDescriptorType, *current_class);
+			return -EINVAL;
+		}
 
 	case USB_DT_OTG:
 		if (length != sizeof(struct usb_otg_descriptor))
@@ -2058,6 +2071,7 @@ static int __must_check ffs_do_descs(unsigned count, char *data, unsigned len,
 {
 	const unsigned _len = len;
 	unsigned long num = 0;
+	int current_class = -1;
 
 	ENTER();
 
@@ -2078,7 +2092,8 @@ static int __must_check ffs_do_descs(unsigned count, char *data, unsigned len,
 		if (!data)
 			return _len - len;
 
-		ret = ffs_do_single_desc(data, len, entity, priv);
+		ret = ffs_do_single_desc(data, len, entity, priv,
+			&current_class);
 		if (unlikely(ret < 0)) {
 			pr_debug("%s returns %d\n", __func__, ret);
 			return ret;

include/linux/usb/ccid.h

+/*
+ *  Copyright (c) 2018  Vincent Pelletier
+ */
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+#ifndef __CCID_H
+#define __CCID_H
+
+#include <linux/types.h>
+
+#define USB_INTERFACE_CLASS_CCID 0x0b
+
+struct ccid_descriptor {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__le16 bcdCCID;
+	__u8  bMaxSlotIndex;
+	__u8  bVoltageSupport;
+	__le32 dwProtocols;
+	__le32 dwDefaultClock;
+	__le32 dwMaximumClock;
+	__u8  bNumClockSupported;
+	__le32 dwDataRate;
+	__le32 dwMaxDataRate;
+	__u8  bNumDataRatesSupported;
+	__le32 dwMaxIFSD;
+	__le32 dwSynchProtocols;
+	__le32 dwMechanical;
+	__le32 dwFeatures;
+	__le32 dwMaxCCIDMessageLength;
+	__u8  bClassGetResponse;
+	__u8  bClassEnvelope;
+	__le16 wLcdLayout;
+	__u8  bPINSupport;
+	__u8  bMaxCCIDBusySlots;
+} __attribute__ ((packed));
+
+#endif /* __CCID_H */