diff options
Diffstat (limited to 'drivers/usb/serial/safe_serial.c')
| -rw-r--r-- | drivers/usb/serial/safe_serial.c | 301 |
1 files changed, 301 insertions, 0 deletions
diff --git a/drivers/usb/serial/safe_serial.c b/drivers/usb/serial/safe_serial.c new file mode 100644 index 000000000..6accbecb6 --- /dev/null +++ b/drivers/usb/serial/safe_serial.c @@ -0,0 +1,301 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Safe Encapsulated USB Serial Driver + * + * Copyright (C) 2010 Johan Hovold <jhovold@gmail.com> + * Copyright (C) 2001 Lineo + * Copyright (C) 2001 Hewlett-Packard + * + * 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/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> + +static bool safe = true; +static bool padded = IS_ENABLED(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 const 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 inline __u16 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; + + if (length < 2) { + dev_err(&port->dev, "malformed packet\n"); + return; + } + + 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 = true; + 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); |