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>

3 files changed, 235 insertions, 27 deletions

diff --git a/drivers/usb/gadget/f_acm.c b/drivers/usb/gadget/f_acm.c
index f3bf5612af2d..5ee1590b8e9c 100644
--- a/drivers/usb/gadget/f_acm.c
+++ b/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 @@ fail:
 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 */
diff --git a/drivers/usb/gadget/u_serial.c b/drivers/usb/gadget/u_serial.c
index 6641efa55639..53d59287f2bc 100644
--- a/drivers/usb/gadget/u_serial.c
+++ b/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);
diff --git a/drivers/usb/gadget/u_serial.h b/drivers/usb/gadget/u_serial.h
index 7b561138f90e..af3910d01aea 100644
--- a/drivers/usb/gadget/u_serial.h
+++ b/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);