path: root/tmk_core/protocol/vusb/usbdrv/usbdrv.c

/* Name: usbdrv.c
 * Project: V-USB, virtual USB port for Atmel's(r) AVR(r) microcontrollers
 * Author: Christian Starkjohann
 * Creation Date: 2004-12-29
 * Tabsize: 4
 * Copyright: (c) 2005 by OBJECTIVE DEVELOPMENT Software GmbH
 * License: GNU GPL v2 (see License.txt), GNU GPL v3 or proprietary (CommercialLicense.txt)
 * This Revision: $Id: usbdrv.c 791 2010-07-15 15:56:13Z cs $
 */

#include "usbportability.h"
#include "usbdrv.h"
#include "oddebug.h"

/*
General Description:
This module implements the C-part of the USB driver. See usbdrv.h for a
documentation of the entire driver.
*/

/* ------------------------------------------------------------------------- */

/* raw USB registers / interface to assembler code: */
uchar          usbRxBuf[2 * USB_BUFSIZE]; /* raw RX buffer: PID, 8 bytes data, 2 bytes CRC */
uchar          usbInputBufOffset;         /* offset in usbRxBuf used for low level receiving */
uchar          usbDeviceAddr;             /* assigned during enumeration, defaults to 0 */
uchar          usbNewDeviceAddr;          /* device ID which should be set after status phase */
uchar          usbConfiguration;          /* currently selected configuration. Administered by driver, but not used */
volatile schar usbRxLen;                  /* = 0; number of bytes in usbRxBuf; 0 means free, -1 for flow control */
uchar          usbCurrentTok;             /* last token received or endpoint number for last OUT token if != 0 */
uchar          usbRxToken;                /* token for data we received; or endpont number for last OUT */
volatile uchar usbTxLen = USBPID_NAK;     /* number of bytes to transmit with next IN token or handshake token */
uchar          usbTxBuf[USB_BUFSIZE];     /* data to transmit with next IN, free if usbTxLen contains handshake token */
#if USB_COUNT_SOF
volatile uchar usbSofCount; /* incremented by assembler module every SOF */
#endif
#if USB_CFG_HAVE_INTRIN_ENDPOINT && !USB_CFG_SUPPRESS_INTR_CODE
usbTxStatus_t usbTxStatus1;
#    if USB_CFG_HAVE_INTRIN_ENDPOINT3
usbTxStatus_t usbTxStatus3;
#    endif
#endif
#if USB_CFG_CHECK_DATA_TOGGLING
uchar usbCurrentDataToken; /* when we check data toggling to ignore duplicate packets */
#endif

/* USB status registers / not shared with asm code */
uchar *            usbMsgPtr;              /* data to transmit next -- ROM or RAM address */
static usbMsgLen_t usbMsgLen = USB_NO_MSG; /* remaining number of bytes */
static uchar       usbMsgFlags;            /* flag values see below */

#define USB_FLG_MSGPTR_IS_ROM (1 << 6)
#define USB_FLG_USE_USER_RW (1 << 7)

/*
optimizing hints:
- do not post/pre inc/dec integer values in operations
- assign value of USB_READ_FLASH() to register variables and don't use side effects in arg
- use narrow scope for variables which should be in X/Y/Z register
- assign char sized expressions to variables to force 8 bit arithmetics
*/

/* -------------------------- String Descriptors --------------------------- */

#if USB_CFG_DESCR_PROPS_STRINGS == 0

#    if USB_CFG_DESCR_PROPS_STRING_0 == 0
#        undef USB_CFG_DESCR_PROPS_STRING_0
#        define USB_CFG_DESCR_PROPS_STRING_0 sizeof(usbDescriptorString0)
const PROGMEM char usbDescriptorString0[] = {
    /* language descriptor */
    4,          /* sizeof(usbDescriptorString0): length of descriptor in bytes */
    3,          /* descriptor type */
    0x09, 0x04, /* language index (0x0409 = US-English) */
};
#    endif

#    if USB_CFG_DESCR_PROPS_STRING_VENDOR == 0 && USB_CFG_VENDOR_NAME_LEN
#        undef USB_CFG_DESCR_PROPS_STRING_VENDOR
#        define USB_CFG_DESCR_PROPS_STRING_VENDOR sizeof(usbDescriptorStringVendor)
const PROGMEM int usbDescriptorStringVendor[] = {USB_STRING_DESCRIPTOR_HEADER(USB_CFG_VENDOR_NAME_LEN), USB_CFG_VENDOR_NAME};
#    endif

#    if USB_CFG_DESCR_PROPS_STRING_PRODUCT == 0 && USB_CFG_DEVICE_NAME_LEN
#        undef USB_CFG_DESCR_PROPS_STRING_PRODUCT
#        define USB_CFG_DESCR_PROPS_STRING_PRODUCT sizeof(usbDescriptorStringDevice)
const PROGMEM int usbDescriptorStringDevice[] = {USB_STRING_DESCRIPTOR_HEADER(USB_CFG_DEVICE_NAME_LEN), USB_CFG_DEVICE_NAME};
#    endif

#    if USB_CFG_DESCR_PROPS_STRING_SERIAL_NUMBER == 0 && USB_CFG_SERIAL_NUMBER_LEN
#        undef USB_CFG_DESCR_PROPS_STRING_SERIAL_NUMBER
#        define USB_CFG_DESCR_PROPS_STRING_SERIAL_NUMBER sizeof(usbDescriptorStringSerialNumber)
const PROGMEM int usbDescriptorStringSerialNumber[] = {USB_STRING_DESCRIPTOR_HEADER(USB_CFG_SERIAL_NUMBER_LEN), USB_CFG_SERIAL_NUMBER};
#    endif

#endif /* USB_CFG_DESCR_PROPS_STRINGS == 0 */

/* --------------------------- Device Descriptor --------------------------- */

#if USB_CFG_DESCR_PROPS_DEVICE == 0
#    undef USB_CFG_DESCR_PROPS_DEVICE
#    define USB_CFG_DESCR_PROPS_DEVICE sizeof(usbDescriptorDevice)
const PROGMEM char usbDescriptorDevice[] = {
    /* USB device descriptor */
    18,                                               /* sizeof(usbDescriptorDevice): length of descriptor in bytes */
    USBDESCR_DEVICE,                                  /* descriptor type */
    0x10, 0x01,                                       /* USB version supported */
    USB_CFG_DEVICE_CLASS, USB_CFG_DEVICE_SUBCLASS, 0, /* protocol */
    8,                                                /* max packet size */
    /* the following two casts affect the first byte of the constant only, but
     * that's sufficient to avoid a warning with the default values.
     */
    (char)USB_CFG_VENDOR_ID,                               /* 2 bytes */
    (char)USB_CFG_DEVICE_ID,                               /* 2 bytes */
    USB_CFG_DEVICE_VERSION,                                /* 2 bytes */
    USB_CFG_DESCR_PROPS_STRING_VENDOR != 0 ? 1 : 0,        /* manufacturer string index */
    USB_CFG_DESCR_PROPS_STRING_PRODUCT != 0 ? 2 : 0,       /* product string index */
    USB_CFG_DESCR_PROPS_STRING_SERIAL_NUMBER != 0 ? 3 : 0, /* serial number string index */
    1,                                                     /* number of configurations */
};
#endif

/* ----------------------- Configuration Descriptor ------------------------ */

#if USB_CFG_DESCR_PROPS_HID_REPORT != 0 && USB_CFG_DESCR_PROPS_HID == 0
#    undef USB_CFG_DESCR_PROPS_HID
#    define USB_CFG_DESCR_PROPS_HID 9 /* length of HID descriptor in config descriptor below */
#endif

#if USB_CFG_DESCR_PROPS_CONFIGURATION == 0
#    undef USB_CFG_DESCR_PROPS_CONFIGURATION
#    define USB_CFG_DESCR_PROPS_CONFIGURATION sizeof(usbDescriptorConfiguration)
PROGMEM char usbDescriptorConfiguration[] = {
    /* USB configuration descriptor */
    9,               /* sizeof(usbDescriptorConfiguration): length of descriptor in bytes */
    USBDESCR_CONFIG, /* descriptor type */
    18 + 7 * USB_CFG_HAVE_INTRIN_ENDPOINT + 7 * USB_CFG_HAVE_INTRIN_ENDPOINT3 + (USB_CFG_DESCR_PROPS_HID & 0xff), 0,
    /* total length of data returned (including inlined descriptors) */
    1, /* number of interfaces in this configuration */
    1, /* index of this configuration */
    0, /* configuration name string index */
#    if USB_CFG_IS_SELF_POWERED
    (1 << 7) | USBATTR_SELFPOWER, /* attributes */
#    else
    (1 << 7), /* attributes */
#    endif
    USB_CFG_MAX_BUS_POWER / 2,                                                          /* max USB current in 2mA units */
                                                                                        /* interface descriptor follows inline: */
    9,                                                                                  /* sizeof(usbDescrInterface): length of descriptor in bytes */
    USBDESCR_INTERFACE,                                                                 /* descriptor type */
    0,                                                                                  /* index of this interface */
    0,                                                                                  /* alternate setting for this interface */
    USB_CFG_HAVE_INTRIN_ENDPOINT + USB_CFG_HAVE_INTRIN_ENDPOINT3,                       /* endpoints excl 0: number of endpoint descriptors to follow */
    USB_CFG_INTERFACE_CLASS, USB_CFG_INTERFACE_SUBCLASS, USB_CFG_INTERFACE_PROTOCOL, 0, /* string index for interface */
#    if (USB_CFG_DESCR_PROPS_HID & 0xff)                                                /* HID descriptor */
    9,                                                                                  /* sizeof(usbDescrHID): length of descriptor in bytes */
    USBDESCR_HID,                                                                       /* descriptor type: HID */
    0x01, 0x01,                                                                         /* BCD representation of HID version */
    0x00,                                                                               /* target country code */
    0x01,                                                                               /* number of HID Report (or other HID class) Descriptor infos to follow */
    0x22,                                                                               /* descriptor type: report */
    USB_CFG_HID_REPORT_DESCRIPTOR_LENGTH, 0,                                            /* total length of report descriptor */
#    endif
#    if USB_CFG_HAVE_INTRIN_ENDPOINT /* endpoint descriptor for endpoint 1 */
    7,                               /* sizeof(usbDescrEndpoint) */
    USBDESCR_ENDPOINT,               /* descriptor type = endpoint */
    (char)0x81,                      /* IN endpoint number 1 */
    0x03,                            /* attrib: Interrupt endpoint */
    8, 0,                            /* maximum packet size */
    USB_CFG_INTR_POLL_INTERVAL,      /* in ms */
#    endif
#    if USB_CFG_HAVE_INTRIN_ENDPOINT3  /* endpoint descriptor for endpoint 3 */
    7,                                 /* sizeof(usbDescrEndpoint) */
    USBDESCR_ENDPOINT,                 /* descriptor type = endpoint */
    (char)(0x80 | USB_CFG_EP3_NUMBER), /* IN endpoint number 3 */
    0x03,                              /* attrib: Interrupt endpoint */
    8, 0,                              /* maximum packet size */
    USB_CFG_INTR_POLL_INTERVAL,        /* in ms */
#    endif
};
#endif

/* ------------------------------------------------------------------------- */

static inline void usbResetDataToggling(void) {
#if USB_CFG_HAVE_INTRIN_ENDPOINT && !USB_CFG_SUPPRESS_INTR_CODE
    USB_SET_DATATOKEN1(USB_INITIAL_DATATOKEN); /* reset data toggling for interrupt endpoint */
#    if USB_CFG_HAVE_INTRIN_ENDPOINT3
    USB_SET_DATATOKEN3(USB_INITIAL_DATATOKEN); /* reset data toggling for interrupt endpoint */
#    endif
#endif
}

static inline void usbResetStall(void) {
#if USB_CFG_IMPLEMENT_HALT && USB_CFG_HAVE_INTRIN_ENDPOINT
    usbTxLen1 = USBPID_NAK;
#    if USB_CFG_HAVE_INTRIN_ENDPOINT3
    usbTxLen3 = USBPID_NAK;
#    endif
#endif
}

/* ------------------------------------------------------------------------- */

#if !USB_CFG_SUPPRESS_INTR_CODE
#    if USB_CFG_HAVE_INTRIN_ENDPOINT
static void usbGenericSetInterrupt(uchar *data, uchar len, usbTxStatus_t *txStatus) {
    uchar *p;
    char   i;

#        if USB_CFG_IMPLEMENT_HALT
    if (usbTxLen1 == USBPID_STALL) return;
#        endif
    if (txStatus->len & 0x10) {                             /* packet buffer was empty */
        txStatus->buffer[0] ^= USBPID_DATA0 ^ USBPID_DATA1; /* toggle token */
    } else {
        txStatus->len = USBPID_NAK; /* avoid sending outdated (overwritten) interrupt data */
    }
    p = txStatus->buffer + 1;
    i = len;
    do { /* if len == 0, we still copy 1 byte, but that's no problem */
        *p++ = *data++;
    } while (--i > 0); /* loop control at the end is 2 bytes shorter than at beginning */
    usbCrc16Append(&txStatus->buffer[1], len);
    txStatus->len = len + 4; /* len must be given including sync byte */
    DBG2(0x21 + (((int)txStatus >> 3) & 3), txStatus->buffer, len + 3);
}

USB_PUBLIC void usbSetInterrupt(uchar *data, uchar len) { usbGenericSetInterrupt(data, len, &usbTxStatus1); }
#    endif

#    if USB_CFG_HAVE_INTRIN_ENDPOINT3
USB_PUBLIC void usbSetInterrupt3(uchar *data, uchar len) { usbGenericSetInterrupt(data, len, &usbTxStatus3); }
#    endif
#endif /* USB_CFG_SUPPRESS_INTR_CODE */

/* ------------------ utilities for code following below ------------------- */

/* Use defines for the switch statement so that we can choose between an
 * if()else if() and a switch/case based implementation. switch() is more
 * efficient for a LARGE set of sequential choices, if() is better in all other
 * cases.
 */
#if USB_CFG_USE_SWITCH_STATEMENT
#    define SWITCH_START(cmd) \
        switch (cmd) {        \
            {
#    define SWITCH_CASE(value) \
        }                      \
        break;                 \
        case (value): {
#    define SWITCH_CASE2(v1, v2) \
        }                        \
        break;                   \
        case (v1):               \
        case (v2): {
#    define SWITCH_CASE3(v1, v2, v3) \
        }                            \
        break;                       \
        case (v1):                   \
        case (v2):                   \
        case (v3): {
#    define SWITCH_DEFAULT \
        }                  \
        break;             \
        default: {
#    define SWITCH_END \
        }              \
        }
#else
#    define SWITCH_START(cmd) \
        {                     \
            uchar _cmd = cmd; \
            if (0) {
#    define SWITCH_CASE(value) \
        }                      \
        else if (_cmd == (value)) {
#    define SWITCH_CASE2(v1, v2) \
        }                        \
        else if (_cmd == (v1) || _cmd == (v2)) {
#    define SWITCH_CASE3(v1, v2, v3) \
        }                            \
        else if (_cmd == (v1) || _cmd == (v2) || (_cmd == v3)) {
#    define SWITCH_DEFAULT \
        }                  \
        else {
#    define SWITCH_END \
        }              \
        }
#endif

#ifndef USB_RX_USER_HOOK
#    define USB_RX_USER_HOOK(data, len)
#endif
#ifndef USB_SET_ADDRESS_HOOK
#    define USB_SET_ADDRESS_HOOK()
#endif

/* ------------------------------------------------------------------------- */

/* We use if() instead of #if in the macro below because #if can't be used
 * in macros and the compiler optimizes constant conditions anyway.
 * This may cause problems with undefined symbols if compiled without
 * optimizing!
 */
#define GET_DESCRIPTOR(cfgProp, staticName)       \
    if (cfgProp) {                                \
        if ((cfgProp)&USB_PROP_IS_RAM) flags = 0; \
        if ((cfgProp)&USB_PROP_IS_DYNAMIC) {      \
            len = usbFunctionDescriptor(rq);      \
        } else {                                  \
            len       = USB_PROP_LENGTH(cfgProp); \
            usbMsgPtr = (uchar *)(staticName);    \
        }                                         \
    }

/* usbDriverDescriptor() is similar to usbFunctionDescriptor(), but used
 * internally for all types of descriptors.
 */
static inline usbMsgLen_t usbDriverDescriptor(usbRequest_t *rq) {
    usbMsgLen_t len   = 0;
    uchar       flags = USB_FLG_MSGPTR_IS_ROM;

    SWITCH_START(rq->wValue.bytes[1])
    SWITCH_CASE(USBDESCR_DEVICE) /* 1 */
    GET_DESCRIPTOR(USB_CFG_DESCR_PROPS_DEVICE, usbDescriptorDevice)
    SWITCH_CASE(USBDESCR_CONFIG) /* 2 */
    GET_DESCRIPTOR(USB_CFG_DESCR_PROPS_CONFIGURATION, usbDescriptorConfiguration)
    SWITCH_CASE(USBDESCR_STRING) /* 3 */
#if USB_CFG_DESCR_PROPS_STRINGS & USB_PROP_IS_DYNAMIC
    if (USB_CFG_DESCR_PROPS_STRINGS & USB_PROP_IS_RAM) flags = 0;
    len = usbFunctionDescriptor(rq);
#else                              /* USB_CFG_DESCR_PROPS_STRINGS & USB_PROP_IS_DYNAMIC */
    SWITCH_START(rq->wValue.bytes[0])
    SWITCH_CASE(0)
    GET_DESCRIPTOR(USB_CFG_DESCR_PROPS_STRING_0, usbDescriptorString0)
    SWITCH_CASE(1)
    GET_DESCRIPTOR(USB_CFG_DESCR_PROPS_STRING_VENDOR, usbDescriptorStringVendor)
    SWITCH_CASE(2)
    GET_DESCRIPTOR(USB_CFG_DESCR_PROPS_STRING_PRODUCT, usbDescriptorStringDevice)
    SWITCH_CASE(3)
    GET_DESCRIPTOR(USB_CFG_DESCR_PROPS_STRING_SERIAL_NUMBER, usbDescriptorStringSerialNumber)
    SWITCH_DEFAULT
    if (USB_CFG_DESCR_PROPS_UNKNOWN & USB_PROP_IS_DYNAMIC) {
        len = usbFunctionDescriptor(rq);
    }
    SWITCH_END
#endif                             /* USB_CFG_DESCR_PROPS_STRINGS & USB_PROP_IS_DYNAMIC */
#if USB_CFG_DESCR_PROPS_HID_REPORT /* only support HID descriptors if enabled */
    SWITCH_CASE(USBDESCR_HID)      /* 0x21 */
    GET_DESCRIPTOR(USB_CFG_DESCR_PROPS_HID, usbDescriptorConfiguration + 18)
    SWITCH_CASE(USBDESCR_HID_REPORT) /* 0x22 */
    GET_DESCRIPTOR(USB_CFG_DESCR_PROPS_HID_REPORT, usbDescriptorHidReport)
#endif
    SWITCH_DEFAULT
    if (USB_CFG_DESCR_PROPS_UNKNOWN & USB_PROP_IS_DYNAMIC) {
        len = usbFunctionDescriptor(rq);
    }
    SWITCH_END
    usbMsgFlags = flags;
    return len;
}

/* ------------------------------------------------------------------------- */

/* usbDriverSetup() is similar to usbFunctionSetup(), but it's used for
 * standard requests instead of class and custom requests.
 */
static inline usbMsgLen_t usbDriverSetup(usbRequest_t *rq) {
    uchar len = 0, *dataPtr = usbTxBuf + 9; /* there are 2 bytes free space at the end of the buffer */
    uchar value = rq->wValue.bytes[0];
#if USB_CFG_IMPLEMENT_HALT
    uchar index = rq->wIndex.bytes[0];
#endif

    dataPtr[0] = 0; /* default reply common to USBRQ_GET_STATUS and USBRQ_GET_INTERFACE */
    SWITCH_START(rq->bRequest)
    SWITCH_CASE(USBRQ_GET_STATUS)                          /* 0 */
    uchar recipient = rq->bmRequestType & USBRQ_RCPT_MASK; /* assign arith ops to variables to enforce byte size */
    if (USB_CFG_IS_SELF_POWERED && recipient == USBRQ_RCPT_DEVICE) dataPtr[0] = USB_CFG_IS_SELF_POWERED;
#if USB_CFG_IMPLEMENT_HALT
    if (recipient == USBRQ_RCPT_ENDPOINT && index == 0x81) /* request status for endpoint 1 */
        dataPtr[0] = usbTxLen1 == USBPID_STALL;
#endif
    dataPtr[1] = 0;
    len        = 2;
#if USB_CFG_IMPLEMENT_HALT
    SWITCH_CASE2(USBRQ_CLEAR_FEATURE, USBRQ_SET_FEATURE) /* 1, 3 */
    if (value == 0 && index == 0x81) {                   /* feature 0 == HALT for endpoint == 1 */
        usbTxLen1 = rq->bRequest == USBRQ_CLEAR_FEATURE ? USBPID_NAK : USBPID_STALL;
        usbResetDataToggling();
    }
#endif
    SWITCH_CASE(USBRQ_SET_ADDRESS) /* 5 */
    usbNewDeviceAddr = value;
    USB_SET_ADDRESS_HOOK();
    SWITCH_CASE(USBRQ_GET_DESCRIPTOR) /* 6 */
    len = usbDriverDescriptor(rq);
    goto skipMsgPtrAssignment;
    SWITCH_CASE(USBRQ_GET_CONFIGURATION) /* 8 */
    dataPtr = &usbConfiguration;         /* send current configuration value */
    len     = 1;
    SWITCH_CASE(USBRQ_SET_CONFIGURATION) /* 9 */
    usbConfiguration = value;
    usbResetStall();
    SWITCH_CASE(USBRQ_GET_INTERFACE) /* 10 */
    len = 1;
#if USB_CFG_HAVE_INTRIN_ENDPOINT && !USB_CFG_SUPPRESS_INTR_CODE
    SWITCH_CASE(USBRQ_SET_INTERFACE) /* 11 */
    usbResetDataToggling();
    usbResetStall();
#endif
    SWITCH_DEFAULT /* 7=SET_DESCRIPTOR, 12=SYNC_FRAME */
        /* Should we add an optional hook here? */
        SWITCH_END usbMsgPtr = dataPtr;
skipMsgPtrAssignment:
    return len;
}

/* ------------------------------------------------------------------------- */

/* usbProcessRx() is called for every message received by the interrupt
 * routine. It distinguishes between SETUP and DATA packets and processes
 * them accordingly.
 */
static inline void usbProcessRx(uchar *data, uchar len) {
    usbRequest_t *rq = (void *)data;

    /* usbRxToken can be:
     * 0x2d 00101101 (USBPID_SETUP for setup data)
     * 0xe1 11100001 (USBPID_OUT: data phase of setup transfer)
     * 0...0x0f for OUT on endpoint X
     */
    DBG2(0x10 + (usbRxToken & 0xf), data, len + 2); /* SETUP=1d, SETUP-DATA=11, OUTx=1x */
    USB_RX_USER_HOOK(data, len)
#if USB_CFG_IMPLEMENT_FN_WRITEOUT
    if (usbRxToken < 0x10) { /* OUT to endpoint != 0: endpoint number in usbRxToken */
        usbFunctionWriteOut(data, len);
        return;
    }
#endif
    if (usbRxToken == (uchar)USBPID_SETUP) {
        if (len != 8) /* Setup size must be always 8 bytes. Ignore otherwise. */
            return;
        usbMsgLen_t replyLen;
        usbTxBuf[0] = USBPID_DATA0; /* initialize data toggling */
        usbTxLen    = USBPID_NAK;   /* abort pending transmit */
        usbMsgFlags = 0;
        uchar type  = rq->bmRequestType & USBRQ_TYPE_MASK;
        if (type != USBRQ_TYPE_STANDARD) { /* standard requests are handled by driver */
            replyLen = usbFunctionSetup(data);
        } else {
            replyLen = usbDriverSetup(rq);
        }
#if USB_CFG_IMPLEMENT_FN_READ || USB_CFG_IMPLEMENT_FN_WRITE
        if (replyLen == USB_NO_MSG) { /* use user-supplied read/write function */
            /* do some conditioning on replyLen, but on IN transfers only */
            if ((rq->bmRequestType & USBRQ_DIR_MASK) != USBRQ_DIR_HOST_TO_DEVICE) {
                if (sizeof(replyLen) < sizeof(rq->wLength.word)) { /* help compiler with optimizing */
                    replyLen = rq->wLength.bytes[0];
                } else {
                    replyLen = rq->wLength.word;
                }
            }
            usbMsgFlags = USB_FLG_USE_USER_RW;
        } else /* The 'else' prevents that we limit a replyLen of USB_NO_MSG to the maximum transfer len. */
#endif
            if (sizeof(replyLen) < sizeof(rq->wLength.word)) {            /* help compiler with optimizing */
            if (!rq->wLength.bytes[1] && replyLen > rq->wLength.bytes[0]) /* limit length to max */
                replyLen = rq->wLength.bytes[0];
        } else {
            if (replyLen > rq->wLength.word) /* limit length to max */
                replyLen = rq->wLength.word;
        }
        usbMsgLen = replyLen;
    } else { /* usbRxToken must be USBPID_OUT, which means data phase of setup (control-out) */
#if USB_CFG_IMPLEMENT_FN_WRITE
        if (usbMsgFlags & USB_FLG_USE_USER_RW) {
            uchar rval = usbFunctionWrite(data, len);
            if (rval == 0xff) { /* an error occurred */
                usbTxLen = USBPID_STALL;
            } else if (rval != 0) { /* This was the final package */
                usbMsgLen = 0;      /* answer with a zero-sized data packet */
            }
        }
#endif
    }
}

/* ------------------------------------------------------------------------- */

/* This function is similar to usbFunctionRead(), but it's also called for
 * data handled automatically by the driver (e.g. descriptor reads).
 */
static uchar usbDeviceRead(uchar *data, uchar len) {
    if (len > 0) { /* don't bother app with 0 sized reads */
#if USB_CFG_IMPLEMENT_FN_READ
        if (usbMsgFlags & USB_FLG_USE_USER_RW) {
            len = usbFunctionRead(data, len);
        } else
#endif
        {
            uchar i = len, *r = usbMsgPtr;
            if (usbMsgFlags & USB_FLG_MSGPTR_IS_ROM) { /* ROM data */
                do {
                    uchar c = USB_READ_FLASH(r); /* assign to char size variable to enforce byte ops */
                    *data++ = c;
                    r++;
                } while (--i);
            } else { /* RAM data */
                do {
                    *data++ = *r++;
                } while (--i);
            }
            usbMsgPtr = r;
        }
    }
    return len;
}

/* ------------------------------------------------------------------------- */

/* usbBuildTxBlock() is called when we have data to transmit and the
 * interrupt routine's transmit buffer is empty.
 */
static inline void usbBuildTxBlock(void) {
    usbMsgLen_t wantLen;
    uchar       len;

    wantLen = usbMsgLen;
    if (wantLen > 8) wantLen = 8;
    usbMsgLen -= wantLen;
    usbTxBuf[0] ^= USBPID_DATA0 ^ USBPID_DATA1; /* DATA toggling */
    len = usbDeviceRead(usbTxBuf + 1, wantLen);
    if (len <= 8) { /* valid data packet */
        usbCrc16Append(&usbTxBuf[1], len);
        len += 4;     /* length including sync byte */
        if (len < 12) /* a partial package identifies end of message */
            usbMsgLen = USB_NO_MSG;
    } else {
        len       = USBPID_STALL; /* stall the endpoint */
        usbMsgLen = USB_NO_MSG;
    }
    usbTxLen = len;
    DBG2(0x20, usbTxBuf, len - 1);
}

/* ------------------------------------------------------------------------- */

static inline void usbHandleResetHook(uchar notResetState) {
#ifdef USB_RESET_HOOK
    static uchar wasReset;
    uchar        isReset = !notResetState;

    if (wasReset != isReset) {
        USB_RESET_HOOK(isReset);
        wasReset = isReset;
    }
#endif
}

/* ------------------------------------------------------------------------- */

USB_PUBLIC void usbPoll(void) {
    schar len;
    uchar i;

    len = usbRxLen - 3;
    if (len >= 0) {
        /* We could check CRC16 here -- but ACK has already been sent anyway. If you
         * need data integrity checks with this driver, check the CRC in your app
         * code and report errors back to the host. Since the ACK was already sent,
         * retries must be handled on application level.
         * unsigned crc = usbCrc16(buffer + 1, usbRxLen - 3);
         */
        usbProcessRx(usbRxBuf + USB_BUFSIZE + 1 - usbInputBufOffset, len);
#if USB_CFG_HAVE_FLOWCONTROL
        if (usbRxLen > 0) /* only mark as available if not inactivated */
            usbRxLen = 0;
#else
        usbRxLen = 0; /* mark rx buffer as available */
#endif
    }
    if (usbTxLen & 0x10) {             /* transmit system idle */
        if (usbMsgLen != USB_NO_MSG) { /* transmit data pending? */
            usbBuildTxBlock();
        }
    }
    for (i = 20; i > 0; i--) {
        uchar usbLineStatus = USBIN & USBMASK;
        if (usbLineStatus != 0) /* SE0 has ended */
            goto isNotReset;
    }
    /* RESET condition, called multiple times during reset */
    usbNewDeviceAddr = 0;
    usbDeviceAddr    = 0;
    usbResetStall();
    DBG1(0xff, 0, 0);
isNotReset:
    usbHandleResetHook(i);
}

/* ------------------------------------------------------------------------- */

USB_PUBLIC void usbInit(void) {
#if USB_INTR_CFG_SET != 0
    USB_INTR_CFG |= USB_INTR_CFG_SET;
#endif
#if USB_INTR_CFG_CLR != 0
    USB_INTR_CFG &= ~(USB_INTR_CFG_CLR);
#endif
    USB_INTR_ENABLE |= (1 << USB_INTR_ENABLE_BIT);
    usbResetDataToggling();
#if USB_CFG_HAVE_INTRIN_ENDPOINT && !USB_CFG_SUPPRESS_INTR_CODE
    usbTxLen1 = USBPID_NAK;
#    if USB_CFG_HAVE_INTRIN_ENDPOINT3
    usbTxLen3 = USBPID_NAK;
#    endif
#endif
}

/* ------------------------------------------------------------------------- */