usb gadget: issue notifications from ACM function

Update the CDC-ACM gadget code to support the peripheral-to-host
notifications when the tty is opened or closed, or issues a BREAK.
The serial framework code calls new generic hooks; right now only
CDC-ACM uses those hooks.  This resolves several REVISIT comments
in the code.  (Based on a patch from Felipe Balbi.)

Note that this doesn't expose USB_CDC_CAP_BRK to the host, since
this code still rejects USB_CDC_REQ_SEND_BREAK control requests
for host-to-peripheral BREAK signaling (received via /dev/ttyGS*).
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Felipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/gadget/f_acm.c

@@ -47,16 +47,37 @@ struct f_acm {
 	u8				ctrl_id, data_id;
 	u8				port_num;
 
+	u8				pending;
+
+	/* lock is mostly for pending and notify_req ... they get accessed
+	 * by callbacks both from tty (open/close/break) under its spinlock,
+	 * and notify_req.complete() which can't use that lock.
+	 */
+	spinlock_t			lock;
+
 	struct acm_ep_descs		fs;
 	struct acm_ep_descs		hs;
 
 	struct usb_ep			*notify;
 	struct usb_endpoint_descriptor	*notify_desc;
+	struct usb_request		*notify_req;
 
 	struct usb_cdc_line_coding	port_line_coding;	/* 8-N-1 etc */
+
+	/* SetControlLineState request -- CDC 1.1 section 6.2.14 (INPUT) */
 	u16				port_handshake_bits;
-#define RS232_RTS	(1 << 1)	/* unused with full duplex */
-#define RS232_DTR	(1 << 0)	/* host is ready for data r/w */
+#define ACM_CTRL_RTS	(1 << 1)	/* unused with full duplex */
+#define ACM_CTRL_DTR	(1 << 0)	/* host is ready for data r/w */
+
+	/* SerialState notification -- CDC 1.1 section 6.3.5 (OUTPUT) */
+	u16				serial_state;
+#define ACM_CTRL_OVERRUN	(1 << 6)
+#define ACM_CTRL_PARITY		(1 << 5)
+#define ACM_CTRL_FRAMING	(1 << 4)
+#define ACM_CTRL_RI		(1 << 3)
+#define ACM_CTRL_BRK		(1 << 2)
+#define ACM_CTRL_DSR		(1 << 1)
+#define ACM_CTRL_DCD		(1 << 0)
 };
 
 static inline struct f_acm *func_to_acm(struct usb_function *f)
@@ -64,12 +85,17 @@ static inline struct f_acm *func_to_acm(struct usb_function *f)
 	return container_of(f, struct f_acm, port.func);
 }
 
+static inline struct f_acm *port_to_acm(struct gserial *p)
+{
+	return container_of(p, struct f_acm, port);
+}
+
 /*-------------------------------------------------------------------------*/
 
 /* notification endpoint uses smallish and infrequent fixed-size messages */
 
 #define GS_LOG2_NOTIFY_INTERVAL		5	/* 1 << 5 == 32 msec */
-#define GS_NOTIFY_MAXPACKET		8
+#define GS_NOTIFY_MAXPACKET		10	/* notification + 2 bytes */
 
 /* interface and class descriptors: */
 
@@ -115,7 +141,7 @@ static struct usb_cdc_acm_descriptor acm_descriptor __initdata = {
 	.bLength =		sizeof(acm_descriptor),
 	.bDescriptorType =	USB_DT_CS_INTERFACE,
 	.bDescriptorSubType =	USB_CDC_ACM_TYPE,
-	.bmCapabilities =	(1 << 1),
+	.bmCapabilities =	USB_CDC_CAP_LINE,
 };
 
 static struct usb_cdc_union_desc acm_union_desc __initdata = {
@@ -275,6 +301,11 @@ static int acm_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
 
 	/* composite driver infrastructure handles everything except
 	 * CDC class messages; interface activation uses set_alt().
+	 *
+	 * Note CDC spec table 4 lists the ACM request profile.  It requires
+	 * encapsulated command support ... we don't handle any, and respond
+	 * to them by stalling.  Options include get/set/clear comm features
+	 * (not that useful) and SEND_BREAK.
 	 */
 	switch ((ctrl->bRequestType << 8) | ctrl->bRequest) {
 
@@ -310,7 +341,7 @@ static int acm_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
 		value = 0;
 
 		/* FIXME we should not allow data to flow until the
-		 * host sets the RS232_DTR bit; and when it clears
+		 * host sets the ACM_CTRL_DTR bit; and when it clears
 		 * that bit, we should return to that no-flow state.
 		 */
 		acm->port_handshake_bits = w_value;
@@ -348,9 +379,6 @@ static int acm_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
 	/* we know alt == 0, so this is an activation or a reset */
 
 	if (intf == acm->ctrl_id) {
-		/* REVISIT this may need more work when we start to
-		 * send notifications ...
-		 */
 		if (acm->notify->driver_data) {
 			VDBG(cdev, "reset acm control interface %d\n", intf);
 			usb_ep_disable(acm->notify);
@@ -395,6 +423,128 @@ static void acm_disable(struct usb_function *f)
 
 /*-------------------------------------------------------------------------*/
 
+/**
+ * acm_cdc_notify - issue CDC notification to host
+ * @acm: wraps host to be notified
+ * @type: notification type
+ * @value: Refer to cdc specs, wValue field.
+ * @data: data to be sent
+ * @length: size of data
+ * Context: irqs blocked, acm->lock held, acm_notify_req non-null
+ *
+ * Returns zero on sucess or a negative errno.
+ *
+ * See section 6.3.5 of the CDC 1.1 specification for information
+ * about the only notification we issue:  SerialState change.
+ */
+static int acm_cdc_notify(struct f_acm *acm, u8 type, u16 value,
+		void *data, unsigned length)
+{
+	struct usb_ep			*ep = acm->notify;
+	struct usb_request		*req;
+	struct usb_cdc_notification	*notify;
+	const unsigned			len = sizeof(*notify) + length;
+	void				*buf;
+	int				status;
+
+	req = acm->notify_req;
+	acm->notify_req = NULL;
+	acm->pending = false;
+
+	req->length = len;
+	notify = req->buf;
+	buf = notify + 1;
+
+	notify->bmRequestType = USB_DIR_IN | USB_TYPE_CLASS
+			| USB_RECIP_INTERFACE;
+	notify->bNotificationType = type;
+	notify->wValue = cpu_to_le16(value);
+	notify->wIndex = cpu_to_le16(acm->ctrl_id);
+	notify->wLength = cpu_to_le16(length);
+	memcpy(buf, data, length);
+
+	status = usb_ep_queue(ep, req, GFP_ATOMIC);
+	if (status < 0) {
+		ERROR(acm->port.func.config->cdev,
+				"acm ttyGS%d can't notify serial state, %d\n",
+				acm->port_num, status);
+		acm->notify_req = req;
+	}
+
+	return status;
+}
+
+static int acm_notify_serial_state(struct f_acm *acm)
+{
+	struct usb_composite_dev *cdev = acm->port.func.config->cdev;
+	int			status;
+
+	spin_lock(&acm->lock);
+	if (acm->notify_req) {
+		DBG(cdev, "acm ttyGS%d serial state %04x\n",
+				acm->port_num, acm->serial_state);
+		status = acm_cdc_notify(acm, USB_CDC_NOTIFY_SERIAL_STATE,
+				0, &acm->serial_state, sizeof(acm->serial_state));
+	} else {
+		acm->pending = true;
+		status = 0;
+	}
+	spin_unlock(&acm->lock);
+	return status;
+}
+
+static void acm_cdc_notify_complete(struct usb_ep *ep, struct usb_request *req)
+{
+	struct f_acm		*acm = req->context;
+	u8			doit = false;
+
+	/* on this call path we do NOT hold the port spinlock,
+	 * which is why ACM needs its own spinlock
+	 */
+	spin_lock(&acm->lock);
+	if (req->status != -ESHUTDOWN)
+		doit = acm->pending;
+	acm->notify_req = req;
+	spin_unlock(&acm->lock);
+
+	if (doit)
+		acm_notify_serial_state(acm);
+}
+
+/* connect == the TTY link is open */
+
+static void acm_connect(struct gserial *port)
+{
+	struct f_acm		*acm = port_to_acm(port);
+
+	acm->serial_state |= ACM_CTRL_DSR | ACM_CTRL_DCD;
+	acm_notify_serial_state(acm);
+}
+
+static void acm_disconnect(struct gserial *port)
+{
+	struct f_acm		*acm = port_to_acm(port);
+
+	acm->serial_state &= ~(ACM_CTRL_DSR | ACM_CTRL_DCD);
+	acm_notify_serial_state(acm);
+}
+
+static int acm_send_break(struct gserial *port, int duration)
+{
+	struct f_acm		*acm = port_to_acm(port);
+	u16			state;
+
+	state = acm->serial_state;
+	state &= ~ACM_CTRL_BRK;
+	if (duration)
+		state |= ACM_CTRL_BRK;
+
+	acm->serial_state = state;
+	return acm_notify_serial_state(acm);
+}
+
+/*-------------------------------------------------------------------------*/
+
 /* ACM function driver setup/binding */
 static int __init
 acm_bind(struct usb_configuration *c, struct usb_function *f)
@@ -443,8 +593,20 @@ acm_bind(struct usb_configuration *c, struct usb_function *f)
 	acm->notify = ep;
 	ep->driver_data = cdev;	/* claim */
 
+	/* allocate notification */
+	acm->notify_req = gs_alloc_req(ep,
+			sizeof(struct usb_cdc_notification) + 2,
+			GFP_KERNEL);
+	if (!acm->notify_req)
+		goto fail;
+
+	acm->notify_req->complete = acm_cdc_notify_complete;
+	acm->notify_req->context = acm;
+
 	/* copy descriptors, and track endpoint copies */
 	f->descriptors = usb_copy_descriptors(acm_fs_function);
+	if (!f->descriptors)
+		goto fail;
 
 	acm->fs.in = usb_find_endpoint(acm_fs_function,
 			f->descriptors, &acm_fs_in_desc);
@@ -476,8 +638,6 @@ acm_bind(struct usb_configuration *c, struct usb_function *f)
 				f->hs_descriptors, &acm_hs_notify_desc);
 	}
 
-	/* FIXME provide a callback for triggering notifications */
-
 	DBG(cdev, "acm ttyGS%d: %s speed IN/%s OUT/%s NOTIFY/%s\n",
 			acm->port_num,
 			gadget_is_dualspeed(c->cdev->gadget) ? "dual" : "full",
@@ -486,6 +646,9 @@ acm_bind(struct usb_configuration *c, struct usb_function *f)
 	return 0;
 
 fail:
+	if (acm->notify_req)
+		gs_free_req(acm->notify, acm->notify_req);
+
 	/* we might as well release our claims on endpoints */
 	if (acm->notify)
 		acm->notify->driver_data = NULL;
@@ -502,10 +665,13 @@ acm_bind(struct usb_configuration *c, struct usb_function *f)
 static void
 acm_unbind(struct usb_configuration *c, struct usb_function *f)
 {
+	struct f_acm		*acm = func_to_acm(f);
+
 	if (gadget_is_dualspeed(c->cdev->gadget))
 		usb_free_descriptors(f->hs_descriptors);
 	usb_free_descriptors(f->descriptors);
-	kfree(func_to_acm(f));
+	gs_free_req(acm->notify, acm->notify_req);
+	kfree(acm);
 }
 
 /* Some controllers can't support CDC ACM ... */
@@ -569,8 +735,14 @@ int __init acm_bind_config(struct usb_configuration *c, u8 port_num)
 	if (!acm)
 		return -ENOMEM;
 
+	spin_lock_init(&acm->lock);
+
 	acm->port_num = port_num;
 
+	acm->port.connect = acm_connect;
+	acm->port.disconnect = acm_disconnect;
+	acm->port.send_break = acm_send_break;
+
 	acm->port.func.name = "acm";
 	acm->port.func.strings = acm_strings;
 	/* descriptors are per-instance copies */

drivers/usb/gadget/u_serial.c

@@ -60,7 +60,8 @@
  * tty_struct links to the tty/filesystem framework
  *
  * gserial <---> gs_port ... links will be null when the USB link is
- * inactive; managed by gserial_{connect,disconnect}().
+ * inactive; managed by gserial_{connect,disconnect}().  each gserial
+ * instance can wrap its own USB control protocol.
  *	gserial->ioport == usb_ep->driver_data ... gs_port
  *	gs_port->port_usb ... gserial
  *
@@ -181,7 +182,7 @@ static void gs_buf_clear(struct gs_buf *gb)
 /*
  * gs_buf_data_avail
  *
- * Return the number of bytes of data available in the circular
+ * Return the number of bytes of data written into the circular
  * buffer.
  */
 static unsigned gs_buf_data_avail(struct gs_buf *gb)
@@ -282,7 +283,7 @@ gs_buf_get(struct gs_buf *gb, char *buf, unsigned count)
  * Allocate a usb_request and its buffer.  Returns a pointer to the
  * usb_request or NULL if there is an error.
  */
-static struct usb_request *
+struct usb_request *
 gs_alloc_req(struct usb_ep *ep, unsigned len, gfp_t kmalloc_flags)
 {
 	struct usb_request *req;
@@ -306,7 +307,7 @@ gs_alloc_req(struct usb_ep *ep, unsigned len, gfp_t kmalloc_flags)
  *
  * Free a usb_request and its buffer.
  */
-static void gs_free_req(struct usb_ep *ep, struct usb_request *req)
+void gs_free_req(struct usb_ep *ep, struct usb_request *req)
 {
 	kfree(req->buf);
 	usb_ep_free_request(ep, req);
@@ -788,10 +789,13 @@ static int gs_open(struct tty_struct *tty, struct file *file)
 
 	/* if connected, start the I/O stream */
 	if (port->port_usb) {
+		struct gserial	*gser = port->port_usb;
+
 		pr_debug("gs_open: start ttyGS%d\n", port->port_num);
 		gs_start_io(port);
 
-		/* REVISIT for ACM, issue "network connected" event */
+		if (gser->connect)
+			gser->connect(gser);
 	}
 
 	pr_debug("gs_open: ttyGS%d (%p,%p)\n", port->port_num, tty, file);
@@ -818,6 +822,7 @@ static int gs_writes_finished(struct gs_port *p)
 static void gs_close(struct tty_struct *tty, struct file *file)
 {
 	struct gs_port *port = tty->driver_data;
+	struct gserial	*gser;
 
 	spin_lock_irq(&port->port_lock);
 
@@ -837,26 +842,27 @@ static void gs_close(struct tty_struct *tty, struct file *file)
 	port->openclose = true;
 	port->open_count = 0;
 
-	if (port->port_usb)
-		/* REVISIT for ACM, issue "network disconnected" event */;
+	gser = port->port_usb;
+	if (gser && gser->disconnect)
+		gser->disconnect(gser);
 
 	/* wait for circular write buffer to drain, disconnect, or at
 	 * most GS_CLOSE_TIMEOUT seconds; then discard the rest
 	 */
-	if (gs_buf_data_avail(&port->port_write_buf) > 0
-			&& port->port_usb) {
+	if (gs_buf_data_avail(&port->port_write_buf) > 0 && gser) {
 		spin_unlock_irq(&port->port_lock);
 		wait_event_interruptible_timeout(port->drain_wait,
 					gs_writes_finished(port),
 					GS_CLOSE_TIMEOUT * HZ);
 		spin_lock_irq(&port->port_lock);
+		gser = port->port_usb;
 	}
 
 	/* Iff we're disconnected, there can be no I/O in flight so it's
 	 * ok to free the circular buffer; else just scrub it.  And don't
 	 * let the push tasklet fire again until we're re-opened.
 	 */
-	if (port->port_usb == NULL)
+	if (gser == NULL)
 		gs_buf_free(&port->port_write_buf);
 	else
 		gs_buf_clear(&port->port_write_buf);
@@ -974,6 +980,24 @@ static void gs_unthrottle(struct tty_struct *tty)
 	spin_unlock_irqrestore(&port->port_lock, flags);
 }
 
+static int gs_break_ctl(struct tty_struct *tty, int duration)
+{
+	struct gs_port	*port = tty->driver_data;
+	int		status = 0;
+	struct gserial	*gser;
+
+	pr_vdebug("gs_break_ctl: ttyGS%d, send break (%d) \n",
+			port->port_num, duration);
+
+	spin_lock_irq(&port->port_lock);
+	gser = port->port_usb;
+	if (gser && gser->send_break)
+		status = gser->send_break(gser, duration);
+	spin_unlock_irq(&port->port_lock);
+
+	return status;
+}
+
 static const struct tty_operations gs_tty_ops = {
 	.open =			gs_open,
 	.close =		gs_close,
@@ -983,6 +1007,7 @@ static const struct tty_operations gs_tty_ops = {
 	.write_room =		gs_write_room,
 	.chars_in_buffer =	gs_chars_in_buffer,
 	.unthrottle =		gs_unthrottle,
+	.break_ctl =		gs_break_ctl,
 };
 
 /*-------------------------------------------------------------------------*/
@@ -1230,14 +1255,17 @@ int gserial_connect(struct gserial *gser, u8 port_num)
 
 	/* REVISIT if waiting on "carrier detect", signal. */
 
-	/* REVISIT for ACM, issue "network connection" status notification:
-	 * connected if open_count, else disconnected.
+	/* if it's already open, start I/O ... and notify the serial
+	 * protocol about open/close status (connect/disconnect).
 	 */
-
-	/* if it's already open, start I/O */
 	if (port->open_count) {
 		pr_debug("gserial_connect: start ttyGS%d\n", port->port_num);
 		gs_start_io(port);
+		if (gser->connect)
+			gser->connect(gser);
+	} else {
+		if (gser->disconnect)
+			gser->disconnect(gser);
 	}
 
 	spin_unlock_irqrestore(&port->port_lock, flags);

drivers/usb/gadget/u_serial.h

@@ -23,8 +23,7 @@
  * style I/O using the USB peripheral endpoints listed here, including
  * hookups to sysfs and /dev for each logical "tty" device.
  *
- * REVISIT need TTY --> USB event flow too, so ACM can report open/close
- * as carrier detect events.  Model after ECM.  There's more ACM state too.
+ * REVISIT at least ACM could support tiocmget() if needed.
  *
  * REVISIT someday, allow multiplexing several TTYs over these endpoints.
  */
@@ -41,8 +40,17 @@ struct gserial {
 
 	/* REVISIT avoid this CDC-ACM support harder ... */
 	struct usb_cdc_line_coding port_line_coding;	/* 9600-8-N-1 etc */
+
+	/* notification callbacks */
+	void (*connect)(struct gserial *p);
+	void (*disconnect)(struct gserial *p);
+	int (*send_break)(struct gserial *p, int duration);
 };
 
+/* utilities to allocate/free request and buffer */
+struct usb_request *gs_alloc_req(struct usb_ep *ep, unsigned len, gfp_t flags);
+void gs_free_req(struct usb_ep *, struct usb_request *req);
+
 /* port setup/teardown is handled by gadget driver */
 int gserial_setup(struct usb_gadget *g, unsigned n_ports);
 void gserial_cleanup(void);