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linux/drivers/usb/serial/safe_serial.c

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/*
* Safe Encapsulated USB Serial Driver
*
* Copyright (C) 2010 Johan Hovold <jhovold@gmail.com>
* Copyright (C) 2001 Lineo
* Copyright (C) 2001 Hewlett-Packard
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* By:
* Stuart Lynne <sl@lineo.com>, Tom Rushworth <tbr@lineo.com>
*/
/*
* The encapsultaion is designed to overcome difficulties with some USB
* hardware.
*
* While the USB protocol has a CRC over the data while in transit, i.e. while
* being carried over the bus, there is no end to end protection. If the
* hardware has any problems getting the data into or out of the USB transmit
* and receive FIFO's then data can be lost.
*
* This protocol adds a two byte trailer to each USB packet to specify the
* number of bytes of valid data and a 10 bit CRC that will allow the receiver
* to verify that the entire USB packet was received without error.
*
* Because in this case the sender and receiver are the class and function
* drivers there is now end to end protection.
*
* There is an additional option that can be used to force all transmitted
* packets to be padded to the maximum packet size. This provides a work
* around for some devices which have problems with small USB packets.
*
* Assuming a packetsize of N:
*
* 0..N-2 data and optional padding
*
* N-2 bits 7-2 - number of bytes of valid data
* bits 1-0 top two bits of 10 bit CRC
* N-1 bottom 8 bits of 10 bit CRC
*
*
* | Data Length | 10 bit CRC |
* + 7 . 6 . 5 . 4 . 3 . 2 . 1 . 0 | 7 . 6 . 5 . 4 . 3 . 2 . 1 . 0 +
*
* The 10 bit CRC is computed across the sent data, followed by the trailer
* with the length set and the CRC set to zero. The CRC is then OR'd into
* the trailer.
*
* When received a 10 bit CRC is computed over the entire frame including
* the trailer and should be equal to zero.
*
* Two module parameters are used to control the encapsulation, if both are
* turned of the module works as a simple serial device with NO
* encapsulation.
*
* See linux/drivers/usbd/serial_fd for a device function driver
* implementation of this.
*
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/gfp.h>
#include <linux/init.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/uaccess.h>
#include <linux/usb.h>
#include <linux/usb/serial.h>
#ifndef CONFIG_USB_SERIAL_SAFE_PADDED
#define CONFIG_USB_SERIAL_SAFE_PADDED 0
#endif
static bool safe = 1;
static bool padded = CONFIG_USB_SERIAL_SAFE_PADDED;
#define DRIVER_AUTHOR "sl@lineo.com, tbr@lineo.com, Johan Hovold <jhovold@gmail.com>"
#define DRIVER_DESC "USB Safe Encapsulated Serial"
MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");
module_param(safe, bool, 0);
MODULE_PARM_DESC(safe, "Turn Safe Encapsulation On/Off");
module_param(padded, bool, 0);
MODULE_PARM_DESC(padded, "Pad to full wMaxPacketSize On/Off");
#define CDC_DEVICE_CLASS 0x02
#define CDC_INTERFACE_CLASS 0x02
#define CDC_INTERFACE_SUBCLASS 0x06
#define LINEO_INTERFACE_CLASS 0xff
#define LINEO_INTERFACE_SUBCLASS_SAFENET 0x01
#define LINEO_SAFENET_CRC 0x01
#define LINEO_SAFENET_CRC_PADDED 0x02
#define LINEO_INTERFACE_SUBCLASS_SAFESERIAL 0x02
#define LINEO_SAFESERIAL_CRC 0x01
#define LINEO_SAFESERIAL_CRC_PADDED 0x02
#define MY_USB_DEVICE(vend, prod, dc, ic, isc) \
.match_flags = USB_DEVICE_ID_MATCH_DEVICE | \
USB_DEVICE_ID_MATCH_DEV_CLASS | \
USB_DEVICE_ID_MATCH_INT_CLASS | \
USB_DEVICE_ID_MATCH_INT_SUBCLASS, \
.idVendor = (vend), \
.idProduct = (prod),\
.bDeviceClass = (dc),\
.bInterfaceClass = (ic), \
.bInterfaceSubClass = (isc),
static struct usb_device_id id_table[] = {
{MY_USB_DEVICE(0x49f, 0xffff, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Itsy */
{MY_USB_DEVICE(0x3f0, 0x2101, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Calypso */
{MY_USB_DEVICE(0x4dd, 0x8001, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Iris */
{MY_USB_DEVICE(0x4dd, 0x8002, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Collie */
{MY_USB_DEVICE(0x4dd, 0x8003, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Collie */
{MY_USB_DEVICE(0x4dd, 0x8004, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Collie */
{MY_USB_DEVICE(0x5f9, 0xffff, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, /* Sharp tmp */
{} /* terminating entry */
};
MODULE_DEVICE_TABLE(usb, id_table);
static const __u16 crc10_table[256] = {
0x000, 0x233, 0x255, 0x066, 0x299, 0x0aa, 0x0cc, 0x2ff,
0x301, 0x132, 0x154, 0x367, 0x198, 0x3ab, 0x3cd, 0x1fe,
0x031, 0x202, 0x264, 0x057, 0x2a8, 0x09b, 0x0fd, 0x2ce,
0x330, 0x103, 0x165, 0x356, 0x1a9, 0x39a, 0x3fc, 0x1cf,
0x062, 0x251, 0x237, 0x004, 0x2fb, 0x0c8, 0x0ae, 0x29d,
0x363, 0x150, 0x136, 0x305, 0x1fa, 0x3c9, 0x3af, 0x19c,
0x053, 0x260, 0x206, 0x035, 0x2ca, 0x0f9, 0x09f, 0x2ac,
0x352, 0x161, 0x107, 0x334, 0x1cb, 0x3f8, 0x39e, 0x1ad,
0x0c4, 0x2f7, 0x291, 0x0a2, 0x25d, 0x06e, 0x008, 0x23b,
0x3c5, 0x1f6, 0x190, 0x3a3, 0x15c, 0x36f, 0x309, 0x13a,
0x0f5, 0x2c6, 0x2a0, 0x093, 0x26c, 0x05f, 0x039, 0x20a,
0x3f4, 0x1c7, 0x1a1, 0x392, 0x16d, 0x35e, 0x338, 0x10b,
0x0a6, 0x295, 0x2f3, 0x0c0, 0x23f, 0x00c, 0x06a, 0x259,
0x3a7, 0x194, 0x1f2, 0x3c1, 0x13e, 0x30d, 0x36b, 0x158,
0x097, 0x2a4, 0x2c2, 0x0f1, 0x20e, 0x03d, 0x05b, 0x268,
0x396, 0x1a5, 0x1c3, 0x3f0, 0x10f, 0x33c, 0x35a, 0x169,
0x188, 0x3bb, 0x3dd, 0x1ee, 0x311, 0x122, 0x144, 0x377,
0x289, 0x0ba, 0x0dc, 0x2ef, 0x010, 0x223, 0x245, 0x076,
0x1b9, 0x38a, 0x3ec, 0x1df, 0x320, 0x113, 0x175, 0x346,
0x2b8, 0x08b, 0x0ed, 0x2de, 0x021, 0x212, 0x274, 0x047,
0x1ea, 0x3d9, 0x3bf, 0x18c, 0x373, 0x140, 0x126, 0x315,
0x2eb, 0x0d8, 0x0be, 0x28d, 0x072, 0x241, 0x227, 0x014,
0x1db, 0x3e8, 0x38e, 0x1bd, 0x342, 0x171, 0x117, 0x324,
0x2da, 0x0e9, 0x08f, 0x2bc, 0x043, 0x270, 0x216, 0x025,
0x14c, 0x37f, 0x319, 0x12a, 0x3d5, 0x1e6, 0x180, 0x3b3,
0x24d, 0x07e, 0x018, 0x22b, 0x0d4, 0x2e7, 0x281, 0x0b2,
0x17d, 0x34e, 0x328, 0x11b, 0x3e4, 0x1d7, 0x1b1, 0x382,
0x27c, 0x04f, 0x029, 0x21a, 0x0e5, 0x2d6, 0x2b0, 0x083,
0x12e, 0x31d, 0x37b, 0x148, 0x3b7, 0x184, 0x1e2, 0x3d1,
0x22f, 0x01c, 0x07a, 0x249, 0x0b6, 0x285, 0x2e3, 0x0d0,
0x11f, 0x32c, 0x34a, 0x179, 0x386, 0x1b5, 0x1d3, 0x3e0,
0x21e, 0x02d, 0x04b, 0x278, 0x087, 0x2b4, 0x2d2, 0x0e1,
};
#define CRC10_INITFCS 0x000 /* Initial FCS value */
#define CRC10_GOODFCS 0x000 /* Good final FCS value */
#define CRC10_FCS(fcs, c) ((((fcs) << 8) & 0x3ff) ^ crc10_table[((fcs) >> 2) & 0xff] ^ (c))
/**
* fcs_compute10 - memcpy and calculate 10 bit CRC across buffer
* @sp: pointer to buffer
* @len: number of bytes
* @fcs: starting FCS
*
* Perform a memcpy and calculate fcs using ppp 10bit CRC algorithm. Return
* new 10 bit FCS.
*/
static __u16 __inline__ fcs_compute10(unsigned char *sp, int len, __u16 fcs)
{
for (; len-- > 0; fcs = CRC10_FCS(fcs, *sp++));
return fcs;
}
static void safe_process_read_urb(struct urb *urb)
{
struct usb_serial_port *port = urb->context;
unsigned char *data = urb->transfer_buffer;
unsigned char length = urb->actual_length;
int actual_length;
__u16 fcs;
if (!length)
return;
if (!safe)
goto out;
fcs = fcs_compute10(data, length, CRC10_INITFCS);
if (fcs) {
dev_err(&port->dev, "%s - bad CRC %x\n", __func__, fcs);
return;
}
actual_length = data[length - 2] >> 2;
if (actual_length > (length - 2)) {
dev_err(&port->dev, "%s - inconsistent lengths %d:%d\n",
__func__, actual_length, length);
return;
}
dev_info(&urb->dev->dev, "%s - actual: %d\n", __func__, actual_length);
length = actual_length;
out:
tty_insert_flip_string(&port->port, data, length);
tty_flip_buffer_push(&port->port);
}
static int safe_prepare_write_buffer(struct usb_serial_port *port,
void *dest, size_t size)
{
unsigned char *buf = dest;
int count;
int trailer_len;
int pkt_len;
__u16 fcs;
trailer_len = safe ? 2 : 0;
count = kfifo_out_locked(&port->write_fifo, buf, size - trailer_len,
&port->lock);
if (!safe)
return count;
/* pad if necessary */
if (padded) {
pkt_len = size;
memset(buf + count, '0', pkt_len - count - trailer_len);
} else {
pkt_len = count + trailer_len;
}
/* set count */
buf[pkt_len - 2] = count << 2;
buf[pkt_len - 1] = 0;
/* compute fcs and insert into trailer */
fcs = fcs_compute10(buf, pkt_len, CRC10_INITFCS);
buf[pkt_len - 2] |= fcs >> 8;
buf[pkt_len - 1] |= fcs & 0xff;
return pkt_len;
}
static int safe_startup(struct usb_serial *serial)
{
struct usb_interface_descriptor *desc;
if (serial->dev->descriptor.bDeviceClass != CDC_DEVICE_CLASS)
return -ENODEV;
desc = &serial->interface->cur_altsetting->desc;
if (desc->bInterfaceClass != LINEO_INTERFACE_CLASS)
return -ENODEV;
if (desc->bInterfaceSubClass != LINEO_INTERFACE_SUBCLASS_SAFESERIAL)
return -ENODEV;
switch (desc->bInterfaceProtocol) {
case LINEO_SAFESERIAL_CRC:
break;
case LINEO_SAFESERIAL_CRC_PADDED:
padded = 1;
break;
default:
return -EINVAL;
}
return 0;
}
static struct usb_serial_driver safe_device = {
.driver = {
.owner = THIS_MODULE,
.name = "safe_serial",
},
.id_table = id_table,
.num_ports = 1,
.process_read_urb = safe_process_read_urb,
.prepare_write_buffer = safe_prepare_write_buffer,
.attach = safe_startup,
};
static struct usb_serial_driver * const serial_drivers[] = {
&safe_device, NULL
};
module_usb_serial_driver(serial_drivers, id_table);
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