[RFC] usb: gadget: f_fs: add capability for dfu run-time descriptor

[David Sands <david.sands@xxxxxxxxx>]

Add the ability for FunctionFS driver to be able to create DFU Run-Time
descriptors.

Signed-off-by: David Sands <david.sands@xxxxxxxxx>
---
 drivers/usb/gadget/function/f_fs.c  | 12 ++++++++++--
 include/uapi/linux/usb/ch9.h        |  4 ++++
 include/uapi/linux/usb/functionfs.h | 10 ++++++++++
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index 73dc10a77cde..ac77ded9e6ad 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -2049,7 +2049,7 @@ 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, int *current_class)
+					   void *priv, int *current_class, int *current_subclass)
 {
 	struct usb_descriptor_header *_ds = (void *)data;
 	u8 length;
@@ -2108,6 +2108,7 @@ static int __must_check ffs_do_single_desc(char *data, unsigned len,
 		if (ds->iInterface)
 			__entity(STRING, ds->iInterface);
 		*current_class = ds->bInterfaceClass;
+		*current_subclass = ds->bInterfaceSubClass;
 	}
 		break;
 
@@ -2132,6 +2133,12 @@ static int __must_check ffs_do_single_desc(char *data, unsigned len,
 			if (length != sizeof(struct ccid_descriptor))
 				goto inv_length;
 			break;
+		} else if (*current_class == USB_CLASS_APP_SPEC &&
+				*current_subclass == USB_SUBCLASS_DFU) {
+			pr_vdebug("dfu functional descriptor\n");
+			if (length != sizeof(struct usb_dfu_functional_descriptor))
+				goto inv_length;
+			break;
 		} else {
 			pr_vdebug("unknown descriptor: %d for class %d\n",
 			      _ds->bDescriptorType, *current_class);
@@ -2194,6 +2201,7 @@ 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;
+	int current_subclass = -1;
 
 	ENTER();
 
@@ -2215,7 +2223,7 @@ static int __must_check ffs_do_descs(unsigned count, char *data, unsigned len,
 			return _len - len;
 
 		ret = ffs_do_single_desc(data, len, entity, priv,
-			&current_class);
+			&current_class, &current_subclass);
 		if (ret < 0) {
 			pr_debug("%s returns %d\n", __func__, ret);
 			return ret;
diff --git a/include/uapi/linux/usb/ch9.h b/include/uapi/linux/usb/ch9.h
index 31fcfa084e63..4683b3b508c7 100644
--- a/include/uapi/linux/usb/ch9.h
+++ b/include/uapi/linux/usb/ch9.h
@@ -266,6 +266,9 @@ struct usb_ctrlrequest {
 /* From the USB 3.1 spec */
 #define	USB_DT_SSP_ISOC_ENDPOINT_COMP	0x31
 
+/* From USB Device Firmware Upgrade Specification, Revision 1.1 */
+#define USB_DT_DFU_FUNCTIONAL		0x21
+
 /* Conventional codes for class-specific descriptors.  The convention is
  * defined in the USB "Common Class" Spec (3.11).  Individual class specs
  * are authoritative for their usage, not the "common class" writeup.
@@ -335,6 +338,7 @@ struct usb_device_descriptor {
 #define USB_CLASS_VENDOR_SPEC		0xff
 
 #define USB_SUBCLASS_VENDOR_SPEC	0xff
+#define USB_SUBCLASS_DFU		0x01
 
 /*-------------------------------------------------------------------------*/
 
diff --git a/include/uapi/linux/usb/functionfs.h b/include/uapi/linux/usb/functionfs.h
index d77ee6b65328..3d15b193b260 100644
--- a/include/uapi/linux/usb/functionfs.h
+++ b/include/uapi/linux/usb/functionfs.h
@@ -37,6 +37,16 @@ struct usb_endpoint_descriptor_no_audio {
 	__u8  bInterval;
 } __attribute__((packed));
 
+/* DFU Functional descriptor */
+struct usb_dfu_functional_descriptor {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bmAttributes;
+	__le16 wDetachTimeOut;
+	__le16 wTransferSize;
+	__le16 bcdDFUVersion;
+} __attribute__ ((packed));
+
 struct usb_functionfs_descs_head_v2 {
 	__le32 magic;
 	__le32 length;
-- 
2.34.1