usb: gadget: f_fs: OS descriptors support

Add support for OS descriptors. The new format of descriptors is used,
because the "flags" field is required for extensions. os_count gives
the number of OSDesc[] elements.
The format of descriptors is given in include/uapi/linux/usb/functionfs.h.

For extended properties descriptor the usb_ext_prop_desc structure covers
only a part of a descriptor, because the wPropertyNameLength is unknown
up front.
Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/u_fs.h

@@ -216,6 +216,13 @@ struct ffs_data {
 	unsigned			fs_descs_count;
 	unsigned			hs_descs_count;
 	unsigned			ss_descs_count;
+	unsigned			ms_os_descs_count;
+	unsigned			ms_os_descs_ext_prop_count;
+	unsigned			ms_os_descs_ext_prop_name_len;
+	unsigned			ms_os_descs_ext_prop_data_len;
+	void				*ms_os_descs_ext_prop_avail;
+	void				*ms_os_descs_ext_prop_name_avail;
+	void				*ms_os_descs_ext_prop_data_avail;
 
 	unsigned short			strings_count;
 	unsigned short			interfaces_count;

include/uapi/linux/usb/functionfs.h

@@ -18,10 +18,9 @@ enum functionfs_flags {
 	FUNCTIONFS_HAS_FS_DESC = 1,
 	FUNCTIONFS_HAS_HS_DESC = 2,
 	FUNCTIONFS_HAS_SS_DESC = 4,
+	FUNCTIONFS_HAS_MS_OS_DESC = 8,
 };
 
-#ifndef __KERNEL__
-
 /* Descriptor of an non-audio endpoint */
 struct usb_endpoint_descriptor_no_audio {
 	__u8  bLength;
@@ -33,6 +32,36 @@ struct usb_endpoint_descriptor_no_audio {
 	__u8  bInterval;
 } __attribute__((packed));
 
+/* MS OS Descriptor header */
+struct usb_os_desc_header {
+	__u8	interface;
+	__le32	dwLength;
+	__le16	bcdVersion;
+	__le16	wIndex;
+	union {
+		struct {
+			__u8	bCount;
+			__u8	Reserved;
+		};
+		__le16	wCount;
+	};
+} __attribute__((packed));
+
+struct usb_ext_compat_desc {
+	__u8	bFirstInterfaceNumber;
+	__u8	Reserved1;
+	__u8	CompatibleID[8];
+	__u8	SubCompatibleID[8];
+	__u8	Reserved2[6];
+};
+
+struct usb_ext_prop_desc {
+	__le32	dwSize;
+	__le32	dwPropertyDataType;
+	__le16	wPropertyNameLength;
+} __attribute__((packed));
+
+#ifndef __KERNEL__
 
 /*
  * Descriptors format:
@@ -45,9 +74,11 @@ struct usb_endpoint_descriptor_no_audio {
  * |     | fs_count  | LE32         | number of full-speed descriptors     |
  * |     | hs_count  | LE32         | number of high-speed descriptors     |
  * |     | ss_count  | LE32         | number of super-speed descriptors    |
+ * |     | os_count  | LE32         | number of MS OS descriptors          |
  * |     | fs_descrs | Descriptor[] | list of full-speed descriptors       |
  * |     | hs_descrs | Descriptor[] | list of high-speed descriptors       |
  * |     | ss_descrs | Descriptor[] | list of super-speed descriptors      |
+ * |     | os_descrs | OSDesc[]     | list of MS OS descriptors            |
  *
  * Depending on which flags are set, various fields may be missing in the
  * structure.  Any flags that are not recognised cause the whole block to be
@@ -74,6 +105,52 @@ struct usb_endpoint_descriptor_no_audio {
  * |   0 | bLength         | U8   | length of the descriptor |
  * |   1 | bDescriptorType | U8   | descriptor type          |
  * |   2 | payload         |      | descriptor's payload     |
+ *
+ * OSDesc[] is an array of valid MS OS Feature Descriptors which have one of
+ * the following formats:
+ *
+ * | off | name            | type | description              |
+ * |-----+-----------------+------+--------------------------|
+ * |   0 | inteface        | U8   | related interface number |
+ * |   1 | dwLength        | U32  | length of the descriptor |
+ * |   5 | bcdVersion      | U16  | currently supported: 1   |
+ * |   7 | wIndex          | U16  | currently supported: 4   |
+ * |   9 | bCount          | U8   | number of ext. compat.   |
+ * |  10 | Reserved        | U8   | 0                        |
+ * |  11 | ExtCompat[]     |      | list of ext. compat. d.  |
+ *
+ * | off | name            | type | description              |
+ * |-----+-----------------+------+--------------------------|
+ * |   0 | inteface        | U8   | related interface number |
+ * |   1 | dwLength        | U32  | length of the descriptor |
+ * |   5 | bcdVersion      | U16  | currently supported: 1   |
+ * |   7 | wIndex          | U16  | currently supported: 5   |
+ * |   9 | wCount          | U16  | number of ext. compat.   |
+ * |  11 | ExtProp[]       |      | list of ext. prop. d.    |
+ *
+ * ExtCompat[] is an array of valid Extended Compatiblity descriptors
+ * which have the following format:
+ *
+ * | off | name                  | type | description                         |
+ * |-----+-----------------------+------+-------------------------------------|
+ * |   0 | bFirstInterfaceNumber | U8   | index of the interface or of the 1st|
+ * |     |                       |      | interface in an IAD group           |
+ * |   1 | Reserved              | U8   | 0                                   |
+ * |   2 | CompatibleID          | U8[8]| compatible ID string                |
+ * |  10 | SubCompatibleID       | U8[8]| subcompatible ID string             |
+ * |  18 | Reserved              | U8[6]| 0                                   |
+ *
+ * ExtProp[] is an array of valid Extended Properties descriptors
+ * which have the following format:
+ *
+ * | off | name                  | type | description                         |
+ * |-----+-----------------------+------+-------------------------------------|
+ * |   0 | dwSize                | U32  | length of the descriptor            |
+ * |   4 | dwPropertyDataType    | U32  | 1..7                                |
+ * |   8 | wPropertyNameLength   | U16  | bPropertyName length (NL)           |
+ * |  10 | bPropertyName         |U8[NL]| name of this property               |
+ * |10+NL| dwPropertyDataLength  | U32  | bPropertyData length (DL)           |
+ * |14+NL| bProperty             |U8[DL]| payload of this property            |
  */
 
 struct usb_functionfs_strings_head {