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libshut.c

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/*!
 * @file libshut.c
 * @brief HID Library - Serial SHUT communication sub driver
 *
 * @author Copyright (C)
 *  2006 - 2007 Arnaud Quette <aquette.dev@gmail.com>
 *
 *      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.
 *
 *      This program is distributed in the hope that it will be useful,
 *      but WITHOUT ANY WARRANTY; without even the implied warranty of
 *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *      GNU General Public License for more details.
 *
 *      You should have received a copy of the GNU General Public License
 *      along with this program; if not, write to the Free Software
 *      Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * -------------------------------------------------------------------------- */

/* TODO list
 * - cleanup, cleanup, cleanup
 * - manage interrupt and complete libshut_get_interrupt / shut_control_msg routing
 * - complete shut_strerror
 * - validate / complete commands and data table in mge-hid from mge-shut
 */

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <string.h>

#include "nut_stdint.h" /* for uint8_t, uint16_t, uint32_t */

#include "serial.h"
#include "libshut.h"
#include "common.h" /* for xmalloc, upsdebugx prototypes */

#define SHUT_DRIVER_NAME      "MGE SHUT communication driver"
#define SHUT_DRIVER_VERSION   "0.80"
#define MAX_TRY 4

/*!
 * HID descriptor, completed with desc{type,len}
 */
00049 struct my_hid_descriptor {
        uint8_t  bLength;
        uint8_t  bDescriptorType;
        uint16_t bcdHID;
        uint8_t  bCountryCode;
        uint8_t  bNumDescriptors;
        uint8_t  bReportDescriptorType;
        uint16_t wDescriptorLength;
};

/*!********************************************************
 * USB spec information, synchronised with (ripped from) libusb
 */

/*
 * Device and/or Interface Class codes
 */
00066 #define USB_CLASS_PER_INTERFACE           0     /* for DeviceClass */
#define USB_CLASS_AUDIO             1
#define USB_CLASS_COMM              2
#define USB_CLASS_HID               3
#define USB_CLASS_PRINTER           7
#define USB_CLASS_MASS_STORAGE            8
#define USB_CLASS_HUB               9
#define USB_CLASS_DATA              10
#define USB_CLASS_VENDOR_SPEC       0xff

/*
 * Descriptor types
 */
#define USB_DT_DEVICE               0x01
#define USB_DT_CONFIG               0x02
#define USB_DT_STRING               0x03
#define USB_DT_INTERFACE            0x04
#define USB_DT_ENDPOINT             0x05

#define USB_DT_HID                  0x21
#define USB_DT_REPORT               0x22
#define USB_DT_PHYSICAL             0x23
#define USB_DT_HUB                  0x29

/*
 * Descriptor sizes per descriptor type
 */
#define USB_DT_DEVICE_SIZE          18
#define USB_DT_CONFIG_SIZE          9
#define USB_DT_INTERFACE_SIZE       9
#define USB_DT_ENDPOINT_SIZE        7
#define USB_DT_ENDPOINT_AUDIO_SIZE  9     /* Audio extension */
#define USB_DT_HUB_NONVAR_SIZE            7

/*
 * Standard requests
 */
#define USB_REQ_GET_STATUS              0x00
#define USB_REQ_CLEAR_FEATURE           0x01
/* 0x02 is reserved */
#define USB_REQ_SET_FEATURE             0x03
/* 0x04 is reserved */
#define USB_REQ_SET_ADDRESS             0x05
#define USB_REQ_GET_DESCRIPTOR          0x06
#define USB_REQ_SET_DESCRIPTOR          0x07
#define USB_REQ_GET_CONFIGURATION       0x08
#define USB_REQ_SET_CONFIGURATION       0x09
#define USB_REQ_GET_INTERFACE           0x0A
#define USB_REQ_SET_INTERFACE           0x0B
#define USB_REQ_SYNCH_FRAME             0x0C

#define USB_TYPE_STANDARD               (0x00 << 5)
#define USB_TYPE_CLASS                  (0x01 << 5)
#define USB_TYPE_VENDOR                 (0x02 << 5)
#define USB_TYPE_RESERVED               (0x03 << 5)

#define USB_RECIP_DEVICE                0x00
#define USB_RECIP_INTERFACE             0x01
#define USB_RECIP_ENDPOINT              0x02
#define USB_RECIP_OTHER                 0x03

/*
 * Various libusb API related stuff
 */
#define USB_ENDPOINT_IN                 0x80
#define USB_ENDPOINT_OUT                0x00
/*!
 * end of USB spec information
 *********************************************************/

/*!
 * HID definitions
 */
00139 #define HID_REPORT_TYPE_INPUT 0x01
#define HID_REPORT_TYPE_OUTPUT      0x02
#define HID_REPORT_TYPE_FEATURE     0x03

#define REQUEST_TYPE_USB        0x80
#define REQUEST_TYPE_HID        0x81
#define REQUEST_TYPE_GET_REPORT 0xa1
#define REQUEST_TYPE_SET_REPORT 0x21

#define MAX_REPORT_SIZE         0x1800

/*!
 * SHUT definitions - From Simplified SHUT spec
 */

00154 #define SHUT_TYPE_REQUEST       0x01
#define SHUT_TYPE_RESPONSE      0x04
#define SHUT_TYPE_NOTIFY        0x05
#define SHUT_OK                 0x06
#define SHUT_NOK                0x15
/* sync signals are also used to set the notification level */
#define SHUT_SYNC               0x16 /* complete notifications - not yet managed */
                             /* but needed for some early Ellipse models */
#define SHUT_SYNC_LIGHT         0x17 /* partial notifications */
#define SHUT_SYNC_OFF           0x18 /* disable notifications - only do polling */
#define SHUT_PKT_LAST           0x80

#define SHUT_TIMEOUT 3000

/*!
 * SHUT functions for HID marshalling
 */
int shut_get_descriptor(int upsfd, unsigned char type,
                  unsigned char index, void *buf, int size);
int shut_get_string_simple(int upsfd, int index,
                     char *buf, size_t buflen);
int libshut_get_report(int upsfd, int ReportId,
                   unsigned char *raw_buf, int ReportSize );
int shut_set_report(int upsfd, int id, unsigned char *pkt, int reportlen);
int libshut_get_interrupt(int upsfd, unsigned char *buf,
                    int bufsize, int timeout);
int shut_control_msg(int upsfd, int requesttype, int request,
                 int value, int index, unsigned char *bytes, int size, int timeout);
void libshut_close(int upsfd);

/* FIXME */
char * shut_strerror() { return ""; }

/*!
 * From SHUT specifications
 * sync'ed with libusb
 */

00192 typedef struct shut_ctrltransfer_s {
      uint8_t  bRequestType;
      uint8_t  bRequest;
      uint16_t wValue;
      uint16_t wIndex;
      uint16_t wLength;
      
      uint32_t timeout;      /* in milliseconds */

      /* pointer to data */
      void *data;
      /*   uint8_t  padding[8]; for use with shut_set_report?! */
} shut_ctrltransfer_t;


typedef union hid_data_t {
      shut_ctrltransfer_t  hid_pkt;
      uint8_t raw_pkt[8]; /* max report lengh, was 8 */
} hid_data_t;

typedef struct shut_packet_s {
      uint8_t bType;
      uint8_t bLength;
      hid_data_t    data;
      uint8_t bChecksum;
} shut_packet_t;

typedef union shut_data_t {
      shut_packet_t shut_pkt;
      uint8_t raw_pkt[11];
} shut_data_t;

typedef union hid_desc_data_t {
      struct my_hid_descriptor hid_desc;
      uint8_t    raw_desc[9]; /* max report lengh, aws 9 */
} hid_desc_data_t;

/* Device descriptor */
typedef struct device_descriptor_s {
      uint8_t  bLength;
      uint8_t  bDescriptorType;
      uint16_t bcdUSB;
      uint8_t  bDeviceClass;
      uint8_t  bDeviceSubClass;
      uint8_t  bDeviceProtocol;
      uint8_t  bMaxPacketSize0;
      uint16_t idVendor;
      uint16_t idProduct;
      uint16_t bcdDevice;
      uint8_t  iManufacturer;
      uint8_t  iProduct;
      uint8_t  iSerialNumber;
      uint8_t  bNumConfigurations;
} device_descriptor_t;
#if 0
typedef union device_desc_data_t {
      device_descriptor_t dev_desc;
      uint8_t       raw_desc[18];
} device_desc_data_t;
#endif
/* Low level SHUT (Serial HID UPS Transfer) routines  */
void setline(int upsfd, int set);
int shut_synchronise(int upsfd);
int shut_wait_ack(int upsfd);
int shut_interrupt_read(int upsfd, int ep, unsigned char *bytes,
                  int size, int timeout);
int shut_control_msg(int upsfd, int requesttype, int request, int value,
                 int index, unsigned char *bytes, int size, int timeout);


/* Data portability */
/* realign packet data according to Endianess */
#define BYTESWAP(in) (((in & 0xFF) << 8) + ((in & 0xFF00) >> 8))
static void align_request(struct shut_ctrltransfer_s *ctrl )
{
#if WORDS_BIGENDIAN
        /* Sparc/Mips/... are big endian, USB/SHUT little endian */
      (*ctrl).wValue    = BYTESWAP((*ctrl).wValue);
      (*ctrl).wIndex    = BYTESWAP((*ctrl).wIndex);
      (*ctrl).wLength   = BYTESWAP((*ctrl).wLength);
#endif
}

/* On success, fill in the curDevice structure and return the report
 * descriptor length. On failure, return -1.
 * Note: When callback is not NULL, the report descriptor will be
 * passed to this function together with the upsfd and SHUTDevice_t
 * information. This callback should return a value > 0 if the device
 * is accepted, or < 1 if not.
 */
int libshut_open(int *upsfd, SHUTDevice_t *curDevice, char *device_path,
      int (*callback)(int upsfd, SHUTDevice_t *hd, unsigned char *rdbuf, int rdlen))
{
      int ret, res; 
      unsigned char buf[20];
      char string[256];
      struct my_hid_descriptor *desc;
      struct device_descriptor_s *dev_descriptor;
      
      /* report descriptor */
      unsigned char     rdbuf[MAX_REPORT_SIZE];
      int         rdlen;

      upsdebugx(2, "libshut_open: using port %s", device_path);

      /* If device is still open, close it */
      if (*upsfd > 0) {
            ser_close(*upsfd, device_path);
      }

      /* initialize serial port */
      /* FIXME: add variable baudrate detection */
      *upsfd = ser_open(device_path);
      ser_set_speed(*upsfd, device_path, B2400);
      setline(*upsfd, 1);

      /* initialise communication */
      if (!shut_synchronise(*upsfd))
      {
            upsdebugx(2, "No communication with UPS");
            return -1;
      }

      upsdebugx(2, "Communication with UPS established");

      /* we can skip the rest due to serial bus specifics! */
      if (!callback) {
            return 1;
      }

      /* Get DEVICE descriptor */
      dev_descriptor = (struct device_descriptor_s *)buf;
      res = shut_get_descriptor(*upsfd, USB_DT_DEVICE, 0, buf, USB_DT_DEVICE_SIZE);
      /* res = shut_control_msg(devp, USB_ENDPOINT_IN+1, USB_REQ_GET_DESCRIPTOR,
      (USB_DT_DEVICE << 8) + 0, 0, buf, 0x9, SHUT_TIMEOUT); */
      if (res < 0)
      {
            upsdebugx(2, "Unable to get DEVICE descriptor (%s)", shut_strerror());
            return -1;
      }

      if (res < 9)
      {
            upsdebugx(2, "DEVICE descriptor too short (expected %d, got %d)",
                  USB_DT_DEVICE_SIZE, res);
            return -1;
      }

      /* collect the identifying information of this
            device. Note that this is safe, because
            there's no need to claim an interface for
            this (and therefore we do not yet need to
            detach any kernel drivers). */

      free(curDevice->Vendor);
      free(curDevice->Product);
      free(curDevice->Serial);
      free(curDevice->Bus);
      memset(curDevice, '\0', sizeof(*curDevice));

      curDevice->VendorID = dev_descriptor->idVendor;
      curDevice->ProductID = dev_descriptor->idProduct;
      curDevice->Vendor = strdup("MGE UPS SYSTEMS");
      curDevice->Bus = strdup("serial");

      if (dev_descriptor->iProduct) {
            ret = shut_get_string_simple(*upsfd, dev_descriptor->iProduct, string, 0x25);
      } else {
            ret = 0;
      }

      if (ret > 0) {
            curDevice->Product = strdup(string);
      } else {
            curDevice->Product = strdup("unknown");
      }

      if (dev_descriptor->iSerialNumber) {
            ret = shut_get_string_simple(*upsfd, dev_descriptor->iSerialNumber, string, 0x25);
      } else {
            ret = 0;
      }

      if (ret > 0) {
            curDevice->Serial = strdup(string);
      } else {
            curDevice->Serial = strdup("unknown");
      }

      upsdebugx(2, "- VendorID: %04x", curDevice->VendorID);
      upsdebugx(2, "- ProductID: %04x", curDevice->ProductID);
      upsdebugx(2, "- Manufacturer: %s", curDevice->Vendor);
      upsdebugx(2, "- Product: %s", curDevice->Product);
      upsdebugx(2, "- Serial Number: %s", curDevice->Serial);
      upsdebugx(2, "- Bus: %s", curDevice->Bus);
      upsdebugx(2, "Device matches");

      /* Get HID descriptor */
      desc = (struct my_hid_descriptor *)buf;
      res = shut_get_descriptor(*upsfd, USB_DT_HID, 0, buf, 0x9);
      /* res = shut_control_msg(devp, USB_ENDPOINT_IN+1, USB_REQ_GET_DESCRIPTOR,
                  (USB_DT_HID << 8) + 0, 0, buf, 0x9, SHUT_TIMEOUT); */

      if (res < 0)
      {
            upsdebugx(2, "Unable to get HID descriptor (%s)", shut_strerror());
            return -1;
      }

      if (res < 9)
      {
            upsdebugx(2, "HID descriptor too short (expected %d, got %d)", 8, res);
            return -1;
      } 

      /* USB_LE16_TO_CPU(desc->wDescriptorLength); */
      desc->wDescriptorLength = buf[7] | (buf[8] << 8);
      upsdebugx(2, "HID descriptor retrieved (Reportlen = %u)", desc->wDescriptorLength);

/*    if (!dev->config) {
            upsdebugx(2, "  Couldn't retrieve descriptors");
            return -1;
      }*/

      rdlen = desc->wDescriptorLength;

      if (rdlen > (int)sizeof(rdbuf)) {
            upsdebugx(2, "HID descriptor too long %d (max %d)", rdlen, sizeof(rdbuf));
            return -1;
      }

      /* Get REPORT descriptor */
      res = shut_get_descriptor(*upsfd, USB_DT_REPORT, 0, rdbuf, rdlen);
      /* res = shut_control_msg(devp, USB_ENDPOINT_IN+1, USB_REQ_GET_DESCRIPTOR,
                        (USB_DT_REPORT << 8) + 0, 0, ReportDesc, 
                  desc->wDescriptorLength, SHUT_TIMEOUT); */
      if (res == rdlen)
      {
            res = callback(*upsfd, curDevice, rdbuf, rdlen);
            if (res < 1) {
                  upsdebugx(2, "Caller doesn't like this device");
                  return -1;
            }

            upsdebugx(2, "Report descriptor retrieved (Reportlen = %d)", rdlen);
            upsdebugx(2, "Found HID device");
            fflush(stdout);

            return rdlen;
      }

      if (res < 0)
      {
            upsdebugx(2, "Unable to get Report descriptor (%d)", res);
      }
      else
      {
            upsdebugx(2, "Report descriptor too short (expected %d, got %d)", rdlen, res);
      }
      
      upsdebugx(2, "No appropriate HID device found");
      fflush(stdout);

      return -1;
}

void libshut_close(int upsfd)
{
      if (upsfd < 1) {
            return;
      }

      ser_close(upsfd, NULL);
}

/* return the report of ID=type in report 
 * return -1 on failure, report length on success
 */
int libshut_get_report(int upsfd, int ReportId,
                   unsigned char *raw_buf, int ReportSize )
{
      if (upsfd < 1) {
            return 0;
      }

      upsdebugx(4, "Entering libshut_get_report");

      return shut_control_msg(upsfd,
            REQUEST_TYPE_GET_REPORT,
            /* == USB_ENDPOINT_IN + USB_TYPE_CLASS + USB_RECIP_INTERFACE, */
             0x01,
             ReportId+(0x03<<8), /* HID_REPORT_TYPE_FEATURE */
             0, raw_buf, ReportSize, SHUT_TIMEOUT);
}

/* return ReportSize upon success ; -1 otherwise */
int libshut_set_report(int upsfd, int ReportId,
                   unsigned char *raw_buf, int ReportSize )
{
      int ret;
      
      if (upsfd < 1) {
            return 0;
      }
            
      upsdebugx(1, "Entering libshut_set_report (report %x, len %i)",
            ReportId, ReportSize);

      upsdebug_hex (4, "==> Report after set", raw_buf, ReportSize);

      ret = shut_control_msg(upsfd, 
            REQUEST_TYPE_SET_REPORT,
            /* == USB_ENDPOINT_OUT + USB_TYPE_CLASS + USB_RECIP_INTERFACE, */
            0x09,
            ReportId+(0x03<<8), /* HID_REPORT_TYPE_FEATURE */
            0, raw_buf, ReportSize, SHUT_TIMEOUT);
      
      return ((ret == 0) ? ReportSize : ret);
}

int libshut_get_string(int upsfd, int StringIdx, char *buf, size_t buflen)
{
      int ret;
      
      if (upsfd < 1) {
            return -1;
      }

      ret = shut_get_string_simple(upsfd, StringIdx, buf, buflen);
      if (ret > 0)
            upsdebugx(2, "-> String: %s (len = %i/%i)", buf, ret, buflen);
      else
            upsdebugx(2, "- Unable to fetch buf");

      return ret;
}

int libshut_get_interrupt(int upsfd, unsigned char *buf,
                     int bufsize, int timeout)
{
      int ret;

      if (upsfd < 1) {
            return -1;
      }

      /* FIXME: hardcoded interrupt EP => need to get EP descr for IF descr */
      ret = shut_interrupt_read(upsfd, 0x81, buf, bufsize, timeout);
      if (ret > 0)
            upsdebugx(6, " ok");
      else
            upsdebugx(6, " none (%i)", ret);
      
      return ret;
}

shut_communication_subdriver_t shut_subdriver = {
      SHUT_DRIVER_NAME,
      SHUT_DRIVER_VERSION,
      libshut_open,
      libshut_close,
      libshut_get_report,
      libshut_set_report,
      libshut_get_string,
      libshut_get_interrupt
};

/***********************************************************************/
/********** Low level SHUT (Serial HID UPS Transfer) routines **********/
/***********************************************************************/

/*
 * set RTS to on and DTR to off
 * 
 * set : 1 to set comm
 * set : 0 to stop commupsh.
 */
void setline(int upsfd, int set)
{
      if (upsfd < 1) {
            return;
      }

      upsdebugx(3, "entering setline(%i)", set);

      if (set == 1) {
            ser_set_dtr(upsfd, 0);
            ser_set_rts(upsfd, 1);
      } else {
            ser_set_dtr(upsfd, 1);
            ser_set_rts(upsfd, 0);
      }
}

/*****************************************************************************
 * shut_synchronise ()
 * 
 * initiate communication with the UPS
 *
 * return TRUE on success, FALSE on failure
 *
 *****************************************************************************/
int shut_synchronise(int upsfd)
{
      int retCode = 0;
      u_char c = SHUT_SYNC, reply;
      int try;
            
      upsdebugx (2, "entering shut_synchronise()");
      reply = '\0';

      /* FIXME: re enable notification support?
      switch (notification)
      {
            case OFF_NOTIFICATION:
                  c = SHUT_SYNC_OFF;
                  break;
            case LIGHT_NOTIFICATION:
                  c = SHUT_SYNC_LIGHT;
                  break;
            default:
            case COMPLETE_NOTIFICATION:
                  c = SHUT_SYNC;
                  break;
      }
      */

      /* Sync with the UPS according to notification */
      for (try = 0; try < MAX_TRY; try++)
      {
            upsdebugx (3, "Syncing communication (try %i)", try);

            if ((ser_send_char(upsfd, c)) == -1)
            {
                  upsdebugx (3, "Communication error while writing to port");
                  continue;
            }

            ser_get_char(upsfd, &reply, 1, 0);
            if (reply == c)
            {
                  upsdebugx (3, "Syncing and notification setting done");
                  return 1;
            }
      }
      return retCode;
}

/*!
 * Compute a SHUT checksum for the packet "buf"
 */
00643 u_char shut_checksum(const u_char *buf, int bufsize)
{
      int i;
      u_char chk=0;
      
      for(i=0; i<bufsize; i++)
            chk^=buf[i];

      upsdebugx (4, "shut_checksum: %02x", chk);
      return chk;
}


int shut_packet_recv(int upsfd, u_char *Buf, int datalen)
{
      u_char   Start[2];
      u_char   Frame[8];
      u_char   Chk[1];
      u_short  Size=8;
      u_short  Pos=0;
      u_char   Retry=0;
      int recv;
      shut_data_t   sdata;
      
      upsdebugx (4, "entering shut_packet_recv (%i)", datalen);
      
      while(datalen>0 && Retry<3)
      {
            /* if(serial_read (SHUT_TIMEOUT, &Start[0]) >= 0) */
            if(ser_get_char(upsfd, &Start[0], SHUT_TIMEOUT/1000, 0) >= 0)
            {
                  sdata.shut_pkt.bType = Start[0];
                  if(Start[0]==SHUT_SYNC)
                  {
                        upsdebugx (4, "received SYNC token");
                        memcpy(Buf, Start, 1);
                        return 1;
                  }
                  else 
                  {
                        /* if((serial_read (SHUT_TIMEOUT, &Start[1]) >= 0) && */
                        if( (ser_get_char(upsfd, &Start[1], SHUT_TIMEOUT/1000, 0) >= 0) &&
                                          ((Start[1]>>4)==(Start[1]&0x0F)))
                        {
                              upsdebug_hex(4, "Receive", Start, 2);
                              Size=Start[1]&0x0F;
                              sdata.shut_pkt.bLength = Size;
                              for(recv=0;recv<Size;recv++)
                              {
                                    /* if(serial_read (SHUT_TIMEOUT, &Frame[recv]) < 0) */
                                    if(ser_get_char(upsfd, &Frame[recv], SHUT_TIMEOUT/1000, 0) < 0)
                                          break;
                              }
                              upsdebug_hex(4, "Receive", Frame, Size);

                              /* serial_read (SHUT_TIMEOUT, &Chk[0]); */
                              ser_get_char(upsfd, &Chk[0], SHUT_TIMEOUT/1000, 0);
                              if(Chk[0]==shut_checksum(Frame, Size))
                              {
                                    upsdebugx (4, "shut_checksum: %02x => OK", Chk[0]);
                                    memcpy(Buf, Frame, Size);
                                    datalen-=Size;
                                    Buf+=Size;
                                    Pos+=Size;
                                    Retry=0;
                              
                                    ser_send_char(upsfd, SHUT_OK);
                                    /* shut_token_send(SHUT_OK); */

                                    if(Start[0]&SHUT_PKT_LAST)
                                    {
                                          if ((Start[0]&SHUT_PKT_LAST) == SHUT_TYPE_NOTIFY)
                                          {
                                                /* TODO: process notification (dropped for now) */
                                                upsdebugx (4, "=> notification");
                                                datalen+=Pos;
                                                Pos=0;
                                          }
                                          else
                                                    return Pos;
                                    }
                                    else
                                          upsdebugx (4, "need more data (%i)!", datalen);
                              }
                              else
                              {
                                    upsdebugx (4, "shut_checksum: %02x => NOK", Chk[0]);
                                    ser_send_char(upsfd, SHUT_NOK);
                                    /* shut_token_send(SHUT_NOK); */
                                    Retry++;
                              }
                        }
                        else
                              return 0;
                  }
            }
            else
                  Retry++;
      } /* while */
      
      return 0;
}

/**********************************************************************/
int shut_interrupt_read(int upsfd, int ep, unsigned char *bytes, int size,
                   int timeout)
{
/*
      usleep(timeout * 1000);
 */
      /* FIXME: to be written */
      return 0;
}

/**********************************************************************/
int shut_get_string_simple(int upsfd, int index,
                     char *buf, size_t buflen)
{
      unsigned char tbuf[255];       /* Some devices choke on size > 255 */
      int ret, si, di;
      
      ret = shut_control_msg(upsfd, USB_ENDPOINT_IN, USB_REQ_GET_DESCRIPTOR,
                  (USB_DT_STRING << 8) + index, 0x0, tbuf, buflen, 1000);
      if (ret < 0)
            return ret;

      if (tbuf[1] != USB_DT_STRING)
            return -EIO;

      if (tbuf[0] > ret)
            return -EFBIG;

      /* skip the zero'ed high bytes */
      for (di = 0, si = 2; si < tbuf[0]; si += 2)
      {
            if (di >= (int)(buflen - 1))
                  break;

            if (tbuf[si + 1])   /* high byte */
                  buf[di++] = '?';
            else
                  buf[di++] = tbuf[si];
      }

      buf[di] = 0;
      return di;
}
            
/* 
 * Human Interface Device (HID) functions
 *********************************************************************/

/**********************************************************************
 * shut_get_descriptor(int desctype, u_char *pkt)
 * 
 * get descriptor specified by DescType and return it in Buf
 *
 * desctype  - from shutdataType
 * pkt       - where to store the report received
 *
 * return 0 on success, -1 on failure, -2 on NACK
 *
 *********************************************************************/
00806 int shut_get_descriptor(int upsfd, unsigned char type,
                  unsigned char index, void *buf, int size)
{
      memset(buf, 0, size);

      upsdebugx (2, "entering shut_get_descriptor(n %02x, %i)", type, size);

      return shut_control_msg(upsfd, USB_ENDPOINT_IN+(type>=USB_DT_HID?1:0),
                         USB_REQ_GET_DESCRIPTOR, (type << 8) + index, 0, buf, size, 1000);
}

/* Take care of a SHUT transfer (sending and receiving data) */
int shut_control_msg(int upsfd, int requesttype, int request,
                int value, int index, unsigned char *bytes, int size, int timeout)
{
      unsigned char shut_pkt[11];
      short Retry=1, set_pass = -1;
      short data_size, remaining_size = size;
      int i;
      struct shut_ctrltransfer_s ctrl;
      int ret = 0;
      
      upsdebugx (3, "entering shut_control_msg");

      /* deal for set requests */
      if (requesttype == REQUEST_TYPE_SET_REPORT)
      {
            set_pass = 1;
            /* add 8 for the first frame that declares a coming set */
            remaining_size+= 8;
      }

      /* build the control request */
      ctrl.bRequestType = requesttype;
      ctrl.bRequest = request;
      ctrl.wValue = value;
      ctrl.wIndex = index;
      ctrl.wLength = size;
      ctrl.data = bytes;
      ctrl.timeout = timeout;

      align_request(&ctrl);

      /* Send all data */
      while(remaining_size > 0 && Retry > 0) {

            if (requesttype == REQUEST_TYPE_SET_REPORT) {
                  if (set_pass == 1) {
                        data_size = 8;
                        set_pass++; /* prepare for the next step */
                  }
                  else {
                        data_size = size;
                        upsdebug_hex(4, "data", bytes, data_size);
                  }
            }
            else
                  data_size = (size >= 8) ? 8 : remaining_size;
            
            /* Forge the SHUT Frame */
            shut_pkt[0] = SHUT_TYPE_REQUEST + ( ((requesttype == REQUEST_TYPE_SET_REPORT) && (remaining_size>8))? 0 : SHUT_PKT_LAST);
            shut_pkt[1] = (data_size<<4) + data_size;
            if ( (requesttype == REQUEST_TYPE_SET_REPORT) && (remaining_size < 8) )
                  memcpy(&shut_pkt[2], bytes, data_size); /* we need to send ctrl.data  */
            else
                  memcpy(&shut_pkt[2], &ctrl, 8);
            shut_pkt[(data_size+3) - 1] = shut_checksum(&shut_pkt[2], data_size);
            
            /* Packets need only to be sent once
            * NACK handling should take care of the rest */
            if (Retry == 1)
            {
                  ser_send_buf(upsfd, shut_pkt, data_size+3);
                  upsdebug_hex(3, "shut_control_msg", shut_pkt, data_size+3);
                  /* serial_send (shut_pkt, data_size+3); */
            }

            i = shut_wait_ack (upsfd);
            switch (i)
            {
                  case 0:
                        if (requesttype == REQUEST_TYPE_SET_REPORT)
                              remaining_size-=data_size;
                        else
                              remaining_size = 0;

                        Retry=1;
                        break;
                  case -1:
                        if (Retry >= MAX_TRY)
                        {
                              upsdebugx(2, "Max tries reached while waiting for ACK, still getting errors");
                              
                              /* try to resync, and give one more try */
                              Retry--;
                              shut_synchronise(upsfd);
                              return i;
                        }
                        else
                        {
                              upsdebugx(4, "Retry = %i", Retry);
                              /* Send a NACK to get a resend from the UPS */
                              ser_send_char(upsfd, SHUT_NOK);
                              Retry++;
                        }
                        break;
                  case -3:
                        /* FIXME: notification caught => to be processed */
                  default:
                        ;
            }
      }
      if (remaining_size != 0)
            return -1;
      
      /* now receive data, except for SET_REPORT */
      if (requesttype != REQUEST_TYPE_SET_REPORT)
            ret = shut_packet_recv (upsfd, bytes, size);

      return ret;
}

/**********************************************************************
 * shut_wait_ack()
 *
 * wait for an ACK packet
 *
 * returns 0 on success, -1 on error, -2 on NACK, -3 on NOTIFICATION
 * 
 *********************************************************************/
int shut_wait_ack(int upsfd)
{
      int retCode = -1;
      u_char c = '\0';

      ser_get_char(upsfd, &c, SHUT_TIMEOUT/1000, 0);
      if (c == SHUT_OK)
      {
            upsdebugx (2, "shut_wait_ack(): ACK received");
            retCode = 0;
      }
      else if (c == SHUT_NOK)
      {
            upsdebugx (2, "shut_wait_ack(): NACK received");
            retCode = -2;
      }
      else if ((c & SHUT_PKT_LAST) == SHUT_TYPE_NOTIFY)
      {
            upsdebugx (2, "shut_wait_ack(): NOTIFY received");
            retCode = -3;
      }
      else if (c == '\0')
            upsdebugx (2, "shut_wait_ack(): Nothing received");
      
      return retCode;
}

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