[PATCH v4] usb: gadget: f_fs: add capability for dfu run-time descriptor

[crwulff@gmail.com]

From: David Sands <david.sands@biamp.com>

From: David Sands <david.sands@biamp.com>

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

Signed-off-by: David Sands <david.sands@biamp.com>
Co-developed-by: Chris Wulff <crwulff@gmail.com>
Signed-off-by: Chris Wulff <crwulff@gmail.com>
---
v4: Clean up unneeded change, switch to BIT macros, more documentation
v3: Documentation, additional constants and constant order fixed
https://lore.kernel.org/all/CO1PR17MB54197F118CBC8783D289B97DE1102@CO1PR17MB5419.namprd17.prod.outlook.com/
v2: https://lore.kernel.org/linux-usb/CO1PR17MB54198D086B61F7392FA9075FE10E2@CO1PR17MB5419.namprd17.prod.outlook.com/
v1: https://lore.kernel.org/linux-usb/CO1PR17MB5419AC3907C74E28D80C5021E1082@CO1PR17MB5419.namprd17.prod.outlook.com/
---
 Documentation/usb/functionfs-desc.rst | 22 ++++++++++++++++++++++
 Documentation/usb/functionfs.rst      |  2 ++
 Documentation/usb/index.rst           |  1 +
 drivers/usb/gadget/function/f_fs.c    | 12 ++++++++++--
 include/uapi/linux/usb/ch9.h          |  8 ++++++--
 include/uapi/linux/usb/functionfs.h   | 25 +++++++++++++++++++++++++
 6 files changed, 66 insertions(+), 4 deletions(-)
 create mode 100644 Documentation/usb/functionfs-desc.rst

diff --git a/Documentation/usb/functionfs-desc.rst b/Documentation/usb/functionfs-desc.rst
new file mode 100644
index 000000000000..73d2b8a3f02c
--- /dev/null
+++ b/Documentation/usb/functionfs-desc.rst
@@ -0,0 +1,22 @@
+======================
+FunctionFS Descriptors
+======================
+
+Interface Descriptors
+---------------------
+
+Standard USB interface descriptors may be added. The class/subclass of the
+most recent interface descriptor determines what type of class-specific
+descriptors are accepted.
+
+Class-Specific Descriptors
+--------------------------
+
+DFU Functional Descriptor
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+When the interface class is USB_CLASS_APP_SPEC and  the interface subclass
+is USB_SUBCLASS_DFU, a DFU functional descriptor can be provided.
+
+.. kernel-doc:: include/uapi/linux/usb/functionfs.h
+   :doc: usb_dfu_functional_descriptor
diff --git a/Documentation/usb/functionfs.rst b/Documentation/usb/functionfs.rst
index d05a775bc45b..4f96e4b93d7b 100644
--- a/Documentation/usb/functionfs.rst
+++ b/Documentation/usb/functionfs.rst
@@ -70,6 +70,8 @@ have been written to their ep0's.
 Conversely, the gadget is unregistered after the first USB function
 closes its endpoints.
 
+For more information about FunctionFS descriptors see :doc:`functionfs-desc`
+
 DMABUF interface
 ================
 
diff --git a/Documentation/usb/index.rst b/Documentation/usb/index.rst
index 27955dad95e1..826492c813ac 100644
--- a/Documentation/usb/index.rst
+++ b/Documentation/usb/index.rst
@@ -11,6 +11,7 @@ USB support
     dwc3
     ehci
     functionfs
+    functionfs-desc
     gadget_configfs
     gadget_hid
     gadget_multi
diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index d8b096859337..ba5c6e4827ba 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -2478,7 +2478,7 @@ 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;
@@ -2535,6 +2535,7 @@ 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;
 
@@ -2559,6 +2560,12 @@ 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);
@@ -2621,6 +2628,7 @@ 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;
 
 	for (;;) {
 		int ret;
@@ -2640,7 +2648,7 @@ 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 44d73ba8788d..91f0f7e214a5 100644
--- a/include/uapi/linux/usb/ch9.h
+++ b/include/uapi/linux/usb/ch9.h
@@ -254,6 +254,9 @@ struct usb_ctrlrequest {
 #define USB_DT_DEVICE_CAPABILITY	0x10
 #define USB_DT_WIRELESS_ENDPOINT_COMP	0x11
 #define USB_DT_WIRE_ADAPTER		0x21
+/* From USB Device Firmware Upgrade Specification, Revision 1.1 */
+#define USB_DT_DFU_FUNCTIONAL		0x21
+/* these are from the Wireless USB spec */
 #define USB_DT_RPIPE			0x22
 #define USB_DT_CS_RADIO_CONTROL		0x23
 /* From the T10 UAS specification */
@@ -329,9 +332,10 @@ struct usb_device_descriptor {
 #define USB_CLASS_USB_TYPE_C_BRIDGE	0x12
 #define USB_CLASS_MISC			0xef
 #define USB_CLASS_APP_SPEC		0xfe
-#define USB_CLASS_VENDOR_SPEC		0xff
+#define USB_SUBCLASS_DFU			0x01
 
-#define USB_SUBCLASS_VENDOR_SPEC	0xff
+#define USB_CLASS_VENDOR_SPEC		0xff
+#define USB_SUBCLASS_VENDOR_SPEC		0xff
 
 /*-------------------------------------------------------------------------*/
 
diff --git a/include/uapi/linux/usb/functionfs.h b/include/uapi/linux/usb/functionfs.h
index 9f88de9c3d66..40f87cbabf7a 100644
--- a/include/uapi/linux/usb/functionfs.h
+++ b/include/uapi/linux/usb/functionfs.h
@@ -37,6 +37,31 @@ struct usb_endpoint_descriptor_no_audio {
 	__u8  bInterval;
 } __attribute__((packed));
 
+/**
+ * struct usb_dfu_functional_descriptor - DFU Functional descriptor
+ * @bLength:		Size of the descriptor (bytes)
+ * @bDescriptorType:	USB_DT_DFU_FUNCTIONAL
+ * @bmAttributes:	DFU attributes
+ * @wDetachTimeOut:	Maximum time to wait after DFU_DETACH (ms, le16)
+ * @wTransferSize:	Maximum number of bytes per control-write (le16)
+ * @bcdDFUVersion:	DFU Spec version (BCD, le16)
+ */
+struct usb_dfu_functional_descriptor {
+	__u8  bLength;
+	__u8  bDescriptorType;
+	__u8  bmAttributes;
+	__le16 wDetachTimeOut;
+	__le16 wTransferSize;
+	__le16 bcdDFUVersion;
+} __attribute__ ((packed));
+
+/* from DFU functional descriptor bmAttributes */
+#define DFU_FUNC_ATT_CAN_DOWNLOAD	BIT(0)
+#define DFU_FUNC_ATT_CAN_UPLOAD		BIT(1)
+#define DFU_FUNC_ATT_MANIFEST_TOLERANT	BIT(2)
+#define DFU_FUNC_ATT_WILL_DETACH	BIT(3)
+
+
 struct usb_functionfs_descs_head_v2 {
 	__le32 magic;
 	__le32 length;
-- 
2.43.0