/* * Safe Encapsulated USB Serial Driver * * Copyright (C) 2010 Johan Hovold * 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 , Tom Rushworth */ /* * 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 #include #include #include #include #include #include #include #include #include #include #include #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 " #define DRIVER_DESC "USB Safe Encapsulated Serial" MODULE_AUTHOR(DRIVER_AUTHOR); MODULE_DESCRIPTION(DRIVER_DESC); MODULE_LICENSE("GPL"); static __u16 vendor; /* no default */ static __u16 product; /* no default */ module_param(vendor, ushort, 0); MODULE_PARM_DESC(vendor, "User specified USB idVendor (required)"); module_param(product, ushort, 0); MODULE_PARM_DESC(product, "User specified USB idProduct (required)"); 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 */ /* extra null entry for module vendor/produc parameters */ {MY_USB_DEVICE(0, 0, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)}, {} /* 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; 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) { switch (serial->interface->cur_altsetting->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 }; static int __init safe_init(void) { int i; /* if we have vendor / product parameters patch them into id list */ if (vendor || product) { pr_info("vendor: %x product: %x\n", vendor, product); for (i = 0; i < ARRAY_SIZE(id_table); i++) { if (!id_table[i].idVendor && !id_table[i].idProduct) { id_table[i].idVendor = vendor; id_table[i].idProduct = product; break; } } } return usb_serial_register_drivers(serial_drivers, KBUILD_MODNAME, id_table); } static void __exit safe_exit(void) { usb_serial_deregister_drivers(serial_drivers); } module_init(safe_init); module_exit(safe_exit);