From 253ca923281aec6975ec4028ddbc58e865d8d13d Mon Sep 17 00:00:00 2001 From: Joris van Rantwijk Date: Thu, 1 Feb 2007 20:08:18 +0100 Subject: USB: add flow control to usb-serial generic driver. I added two fields to struct usb_serial_port to keep track of the throttle state. Other usb-serial drivers typically use private data for such things, but the generic driver can not really do that because some of its code is also used by other drivers (which may have their own private data needs). As it is, I am not sure that this patch is useful in all scenarios. It is certainly helpful for low-bandwidth devices that can hold their data in response to throttling. But for devices that pump data in real-time as fast as possible (webcam, A/D converter, etc), throttling may actually cause more data loss. From: Joris van Rantwijk Signed-off-by: Greg Kroah-Hartman --- drivers/usb/serial/generic.c | 102 +++++++++++++++++++++++++++++++++++-------- 1 file changed, 84 insertions(+), 18 deletions(-) (limited to 'drivers/usb/serial/generic.c') diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c index 601e0648dec6..53baeec8f265 100644 --- a/drivers/usb/serial/generic.c +++ b/drivers/usb/serial/generic.c @@ -66,6 +66,8 @@ struct usb_serial_driver usb_serial_generic_device = { .num_bulk_out = NUM_DONT_CARE, .num_ports = 1, .shutdown = usb_serial_generic_shutdown, + .throttle = usb_serial_generic_throttle, + .unthrottle = usb_serial_generic_unthrottle, }; static int generic_probe(struct usb_interface *interface, @@ -115,6 +117,7 @@ int usb_serial_generic_open (struct usb_serial_port *port, struct file *filp) { struct usb_serial *serial = port->serial; int result = 0; + unsigned long flags; dbg("%s - port %d", __FUNCTION__, port->number); @@ -124,7 +127,13 @@ int usb_serial_generic_open (struct usb_serial_port *port, struct file *filp) if (port->tty) port->tty->low_latency = 1; - /* if we have a bulk interrupt, start reading from it */ + /* clear the throttle flags */ + spin_lock_irqsave(&port->lock, flags); + port->throttled = 0; + port->throttle_req = 0; + spin_unlock_irqrestore(&port->lock, flags); + + /* if we have a bulk endpoint, start reading from it */ if (serial->num_bulk_in) { /* Start reading from the device */ usb_fill_bulk_urb (port->read_urb, serial->dev, @@ -253,31 +262,22 @@ int usb_serial_generic_chars_in_buffer (struct usb_serial_port *port) return (chars); } -void usb_serial_generic_read_bulk_callback (struct urb *urb) +/* Push data to tty layer and resubmit the bulk read URB */ +static void flush_and_resubmit_read_urb (struct usb_serial_port *port) { - struct usb_serial_port *port = (struct usb_serial_port *)urb->context; struct usb_serial *serial = port->serial; - struct tty_struct *tty; - unsigned char *data = urb->transfer_buffer; + struct urb *urb = port->read_urb; + struct tty_struct *tty = port->tty; int result; - dbg("%s - port %d", __FUNCTION__, port->number); - - if (urb->status) { - dbg("%s - nonzero read bulk status received: %d", __FUNCTION__, urb->status); - return; - } - - usb_serial_debug_data(debug, &port->dev, __FUNCTION__, urb->actual_length, data); - - tty = port->tty; + /* Push data to tty */ if (tty && urb->actual_length) { tty_buffer_request_room(tty, urb->actual_length); - tty_insert_flip_string(tty, data, urb->actual_length); - tty_flip_buffer_push(tty); + tty_insert_flip_string(tty, urb->transfer_buffer, urb->actual_length); + tty_flip_buffer_push(tty); /* is this allowed from an URB callback ? */ } - /* Continue trying to always read */ + /* Continue reading from device */ usb_fill_bulk_urb (port->read_urb, serial->dev, usb_rcvbulkpipe (serial->dev, port->bulk_in_endpointAddress), @@ -290,6 +290,40 @@ void usb_serial_generic_read_bulk_callback (struct urb *urb) if (result) dev_err(&port->dev, "%s - failed resubmitting read urb, error %d\n", __FUNCTION__, result); } + +void usb_serial_generic_read_bulk_callback (struct urb *urb) +{ + struct usb_serial_port *port = (struct usb_serial_port *)urb->context; + unsigned char *data = urb->transfer_buffer; + int is_throttled; + unsigned long flags; + + dbg("%s - port %d", __FUNCTION__, port->number); + + if (urb->status) { + dbg("%s - nonzero read bulk status received: %d", __FUNCTION__, urb->status); + return; + } + + usb_serial_debug_data(debug, &port->dev, __FUNCTION__, urb->actual_length, data); + + /* Throttle the device if requested by tty */ + if (urb->actual_length) { + spin_lock_irqsave(&port->lock, flags); + is_throttled = port->throttled = port->throttle_req; + spin_unlock_irqrestore(&port->lock, flags); + if (is_throttled) { + /* Let the received data linger in the read URB; + * usb_serial_generic_unthrottle() will pick it + * up later. */ + dbg("%s - throttling device", __FUNCTION__); + return; + } + } + + /* Handle data and continue reading from device */ + flush_and_resubmit_read_urb(port); +} EXPORT_SYMBOL_GPL(usb_serial_generic_read_bulk_callback); void usb_serial_generic_write_bulk_callback (struct urb *urb) @@ -308,6 +342,38 @@ void usb_serial_generic_write_bulk_callback (struct urb *urb) } EXPORT_SYMBOL_GPL(usb_serial_generic_write_bulk_callback); +void usb_serial_generic_throttle (struct usb_serial_port *port) +{ + unsigned long flags; + + dbg("%s - port %d", __FUNCTION__, port->number); + + /* Set the throttle request flag. It will be picked up + * by usb_serial_generic_read_bulk_callback(). */ + spin_lock_irqsave(&port->lock, flags); + port->throttle_req = 1; + spin_unlock_irqrestore(&port->lock, flags); +} + +void usb_serial_generic_unthrottle (struct usb_serial_port *port) +{ + int was_throttled; + unsigned long flags; + + dbg("%s - port %d", __FUNCTION__, port->number); + + /* Clear the throttle flags */ + spin_lock_irqsave(&port->lock, flags); + was_throttled = port->throttled; + port->throttled = port->throttle_req = 0; + spin_unlock_irqrestore(&port->lock, flags); + + if (was_throttled) { + /* Handle pending data and resume reading from device */ + flush_and_resubmit_read_urb(port); + } +} + void usb_serial_generic_shutdown (struct usb_serial *serial) { int i; -- cgit v1.2.3 From b46d60fc4b2665107a04f75e5381294bfaf20177 Mon Sep 17 00:00:00 2001 From: David Brownell Date: Fri, 23 Mar 2007 12:51:55 -0700 Subject: USB: fix usb-serial/generic build warning Fix annoying build warning when CONFIG_USB_SERIAL_GENERIC is undefined. drivers/usb/serial/generic.c:24: warning: `generic_probe' declared `static' but never defined Signed-off-by: David Brownell Signed-off-by: Greg Kroah-Hartman --- drivers/usb/serial/generic.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'drivers/usb/serial/generic.c') diff --git a/drivers/usb/serial/generic.c b/drivers/usb/serial/generic.c index 53baeec8f265..4f8282ad7720 100644 --- a/drivers/usb/serial/generic.c +++ b/drivers/usb/serial/generic.c @@ -20,13 +20,14 @@ #include #include -static int generic_probe(struct usb_interface *interface, - const struct usb_device_id *id); - static int debug; #ifdef CONFIG_USB_SERIAL_GENERIC + +static int generic_probe(struct usb_interface *interface, + const struct usb_device_id *id); + static __u16 vendor = 0x05f9; static __u16 product = 0xffff; -- cgit v1.2.3