linux/drivers/usb/serial/generic.c
Alan Cox 33f0f88f1c [PATCH] TTY layer buffering revamp
The API and code have been through various bits of initial review by
serial driver people but they definitely need to live somewhere for a
while so the unconverted drivers can get knocked into shape, existing
drivers that have been updated can be better tuned and bugs whacked out.

This replaces the tty flip buffers with kmalloc objects in rings. In the
normal situation for an IRQ driven serial port at typical speeds the
behaviour is pretty much the same, two buffers end up allocated and the
kernel cycles between them as before.

When there are delays or at high speed we now behave far better as the
buffer pool can grow a bit rather than lose characters. This also means
that we can operate at higher speeds reliably.

For drivers that receive characters in blocks (DMA based, USB and
especially virtualisation) the layer allows a lot of driver specific
code that works around the tty layer with private secondary queues to be
removed. The IBM folks need this sort of layer, the smart serial port
people do, the virtualisers do (because a virtualised tty typically
operates at infinite speed rather than emulating 9600 baud).

Finally many drivers had invalid and unsafe attempts to avoid buffer
overflows by directly invoking tty methods extracted out of the innards
of work queue structs. These are no longer needed and all go away. That
fixes various random hangs with serial ports on overflow.

The other change in here is to optimise the receive_room path that is
used by some callers. It turns out that only one ldisc uses receive room
except asa constant and it updates it far far less than the value is
read. We thus make it a variable not a function call.

I expect the code to contain bugs due to the size alone but I'll be
watching and squashing them and feeding out new patches as it goes.

Because the buffers now dynamically expand you should only run out of
buffering when the kernel runs out of memory for real.  That means a lot of
the horrible hacks high performance drivers used to do just aren't needed any
more.

Description:

tty_insert_flip_char is an old API and continues to work as before, as does
tty_flip_buffer_push() [this is why many drivers dont need modification].  It
does now also return the number of chars inserted

There are also

tty_buffer_request_room(tty, len)

which asks for a buffer block of the length requested and returns the space
found.  This improves efficiency with hardware that knows how much to
transfer.

and tty_insert_flip_string_flags(tty, str, flags, len)

to insert a string of characters and flags

For a smart interface the usual code is

    len = tty_request_buffer_room(tty, amount_hardware_says);
    tty_insert_flip_string(tty, buffer_from_card, len);

More description!

At the moment tty buffers are attached directly to the tty.  This is causing a
lot of the problems related to tty layer locking, also problems at high speed
and also with bursty data (such as occurs in virtualised environments)

I'm working on ripping out the flip buffers and replacing them with a pool of
dynamically allocated buffers.  This allows both for old style "byte I/O"
devices and also helps virtualisation and smart devices where large blocks of
data suddenely materialise and need storing.

So far so good.  Lots of drivers reference tty->flip.*.  Several of them also
call directly and unsafely into function pointers it provides.  This will all
break.  Most drivers can use tty_insert_flip_char which can be kept as an API
but others need more.

At the moment I've added the following interfaces, if people think more will
be needed now is a good time to say

 int tty_buffer_request_room(tty, size)

Try and ensure at least size bytes are available, returns actual room (may be
zero).  At the moment it just uses the flipbuf space but that will change.
Repeated calls without characters being added are not cumulative.  (ie if you
call it with 1, 1, 1, and then 4 you'll have four characters of space.  The
other functions will also try and grow buffers in future but this will be a
more efficient way when you know block sizes.

 int tty_insert_flip_char(tty, ch, flag)

As before insert a character if there is room.  Now returns 1 for success, 0
for failure.

 int tty_insert_flip_string(tty, str, len)

Insert a block of non error characters.  Returns the number inserted.

 int tty_prepare_flip_string(tty, strptr, len)

Adjust the buffer to allow len characters to be added.  Returns a buffer
pointer in strptr and the length available.  This allows for hardware that
needs to use functions like insl or mencpy_fromio.

Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Paul Fulghum <paulkf@microgate.com>
Signed-off-by: Hirokazu Takata <takata@linux-m32r.org>
Signed-off-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: John Hawkes <hawkes@sgi.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-10 08:01:59 -08:00

318 lines
8.6 KiB
C

/*
* USB Serial Converter Generic functions
*
* Copyright (C) 1999 - 2002 Greg Kroah-Hartman (greg@kroah.com)
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version
* 2 as published by the Free Software Foundation.
*
*/
#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/usb.h>
#include <asm/uaccess.h>
#include "usb-serial.h"
static int debug;
#ifdef CONFIG_USB_SERIAL_GENERIC
static __u16 vendor = 0x05f9;
static __u16 product = 0xffff;
module_param(vendor, ushort, 0);
MODULE_PARM_DESC(vendor, "User specified USB idVendor");
module_param(product, ushort, 0);
MODULE_PARM_DESC(product, "User specified USB idProduct");
static struct usb_device_id generic_device_ids[2]; /* Initially all zeroes. */
/* All of the device info needed for the Generic Serial Converter */
struct usb_serial_driver usb_serial_generic_device = {
.driver = {
.owner = THIS_MODULE,
.name = "generic",
},
.id_table = generic_device_ids,
.num_interrupt_in = NUM_DONT_CARE,
.num_bulk_in = NUM_DONT_CARE,
.num_bulk_out = NUM_DONT_CARE,
.num_ports = 1,
.shutdown = usb_serial_generic_shutdown,
};
/* we want to look at all devices, as the vendor/product id can change
* depending on the command line argument */
static struct usb_device_id generic_serial_ids[] = {
{.driver_info = 42},
{}
};
static int generic_probe(struct usb_interface *interface,
const struct usb_device_id *id)
{
const struct usb_device_id *id_pattern;
id_pattern = usb_match_id(interface, generic_device_ids);
if (id_pattern != NULL)
return usb_serial_probe(interface, id);
return -ENODEV;
}
static struct usb_driver generic_driver = {
.name = "usbserial_generic",
.probe = generic_probe,
.disconnect = usb_serial_disconnect,
.id_table = generic_serial_ids,
.no_dynamic_id = 1,
};
#endif
int usb_serial_generic_register (int _debug)
{
int retval = 0;
debug = _debug;
#ifdef CONFIG_USB_SERIAL_GENERIC
generic_device_ids[0].idVendor = vendor;
generic_device_ids[0].idProduct = product;
generic_device_ids[0].match_flags = USB_DEVICE_ID_MATCH_VENDOR | USB_DEVICE_ID_MATCH_PRODUCT;
/* register our generic driver with ourselves */
retval = usb_serial_register (&usb_serial_generic_device);
if (retval)
goto exit;
retval = usb_register(&generic_driver);
if (retval)
usb_serial_deregister(&usb_serial_generic_device);
exit:
#endif
return retval;
}
void usb_serial_generic_deregister (void)
{
#ifdef CONFIG_USB_SERIAL_GENERIC
/* remove our generic driver */
usb_deregister(&generic_driver);
usb_serial_deregister (&usb_serial_generic_device);
#endif
}
int usb_serial_generic_open (struct usb_serial_port *port, struct file *filp)
{
struct usb_serial *serial = port->serial;
int result = 0;
dbg("%s - port %d", __FUNCTION__, port->number);
/* force low_latency on so that our tty_push actually forces the data through,
otherwise it is scheduled, and with high data rates (like with OHCI) data
can get lost. */
if (port->tty)
port->tty->low_latency = 1;
/* if we have a bulk interrupt, start reading from it */
if (serial->num_bulk_in) {
/* Start reading from the device */
usb_fill_bulk_urb (port->read_urb, serial->dev,
usb_rcvbulkpipe(serial->dev, port->bulk_in_endpointAddress),
port->read_urb->transfer_buffer,
port->read_urb->transfer_buffer_length,
((serial->type->read_bulk_callback) ?
serial->type->read_bulk_callback :
usb_serial_generic_read_bulk_callback),
port);
result = usb_submit_urb(port->read_urb, GFP_KERNEL);
if (result)
dev_err(&port->dev, "%s - failed resubmitting read urb, error %d\n", __FUNCTION__, result);
}
return result;
}
static void generic_cleanup (struct usb_serial_port *port)
{
struct usb_serial *serial = port->serial;
dbg("%s - port %d", __FUNCTION__, port->number);
if (serial->dev) {
/* shutdown any bulk reads that might be going on */
if (serial->num_bulk_out)
usb_kill_urb(port->write_urb);
if (serial->num_bulk_in)
usb_kill_urb(port->read_urb);
}
}
void usb_serial_generic_close (struct usb_serial_port *port, struct file * filp)
{
dbg("%s - port %d", __FUNCTION__, port->number);
generic_cleanup (port);
}
int usb_serial_generic_write(struct usb_serial_port *port, const unsigned char *buf, int count)
{
struct usb_serial *serial = port->serial;
int result;
unsigned char *data;
dbg("%s - port %d", __FUNCTION__, port->number);
if (count == 0) {
dbg("%s - write request of 0 bytes", __FUNCTION__);
return (0);
}
/* only do something if we have a bulk out endpoint */
if (serial->num_bulk_out) {
spin_lock(&port->lock);
if (port->write_urb_busy) {
spin_unlock(&port->lock);
dbg("%s - already writing", __FUNCTION__);
return 0;
}
port->write_urb_busy = 1;
spin_unlock(&port->lock);
count = (count > port->bulk_out_size) ? port->bulk_out_size : count;
memcpy (port->write_urb->transfer_buffer, buf, count);
data = port->write_urb->transfer_buffer;
usb_serial_debug_data(debug, &port->dev, __FUNCTION__, count, data);
/* set up our urb */
usb_fill_bulk_urb (port->write_urb, serial->dev,
usb_sndbulkpipe (serial->dev,
port->bulk_out_endpointAddress),
port->write_urb->transfer_buffer, count,
((serial->type->write_bulk_callback) ?
serial->type->write_bulk_callback :
usb_serial_generic_write_bulk_callback), port);
/* send the data out the bulk port */
port->write_urb_busy = 1;
result = usb_submit_urb(port->write_urb, GFP_ATOMIC);
if (result) {
dev_err(&port->dev, "%s - failed submitting write urb, error %d\n", __FUNCTION__, result);
/* don't have to grab the lock here, as we will retry if != 0 */
port->write_urb_busy = 0;
} else
result = count;
return result;
}
/* no bulk out, so return 0 bytes written */
return 0;
}
int usb_serial_generic_write_room (struct usb_serial_port *port)
{
struct usb_serial *serial = port->serial;
int room = 0;
dbg("%s - port %d", __FUNCTION__, port->number);
if (serial->num_bulk_out) {
if (!(port->write_urb_busy))
room = port->bulk_out_size;
}
dbg("%s - returns %d", __FUNCTION__, room);
return (room);
}
int usb_serial_generic_chars_in_buffer (struct usb_serial_port *port)
{
struct usb_serial *serial = port->serial;
int chars = 0;
dbg("%s - port %d", __FUNCTION__, port->number);
if (serial->num_bulk_out) {
if (port->write_urb_busy)
chars = port->write_urb->transfer_buffer_length;
}
dbg("%s - returns %d", __FUNCTION__, chars);
return (chars);
}
void usb_serial_generic_read_bulk_callback (struct urb *urb, struct pt_regs *regs)
{
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;
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;
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);
}
/* Continue trying to always read */
usb_fill_bulk_urb (port->read_urb, serial->dev,
usb_rcvbulkpipe (serial->dev,
port->bulk_in_endpointAddress),
port->read_urb->transfer_buffer,
port->read_urb->transfer_buffer_length,
((serial->type->read_bulk_callback) ?
serial->type->read_bulk_callback :
usb_serial_generic_read_bulk_callback), port);
result = usb_submit_urb(port->read_urb, GFP_ATOMIC);
if (result)
dev_err(&port->dev, "%s - failed resubmitting read urb, error %d\n", __FUNCTION__, result);
}
void usb_serial_generic_write_bulk_callback (struct urb *urb, struct pt_regs *regs)
{
struct usb_serial_port *port = (struct usb_serial_port *)urb->context;
dbg("%s - port %d", __FUNCTION__, port->number);
port->write_urb_busy = 0;
if (urb->status) {
dbg("%s - nonzero write bulk status received: %d", __FUNCTION__, urb->status);
return;
}
usb_serial_port_softint((void *)port);
schedule_work(&port->work);
}
EXPORT_SYMBOL_GPL(usb_serial_generic_write_bulk_callback);
void usb_serial_generic_shutdown (struct usb_serial *serial)
{
int i;
dbg("%s", __FUNCTION__);
/* stop reads and writes on all ports */
for (i=0; i < serial->num_ports; ++i) {
generic_cleanup(serial->port[i]);
}
}