os/linux-2.6-tag--devboard-R2_10-4/arch/cris/arch-v32/drivers/elphel/exif353.c

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/*!********************************************************************************
*! FILE NAME  : exif353.c
*! DESCRIPTION: Drivers for Exif manipulation
*! Copyright (C) 2008 Elphel, Inc.
*! -----------------------------------------------------------------------------**
*!
*!  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 3 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, see <http://www.gnu.org/licenses/>.
*! -----------------------------------------------------------------------------**
*!  $Log: exif353.c,v $
*!  Revision 1.1.1.1  2008/11/27 20:04:00  elphel
*!
*!
*!  Revision 1.3  2008/09/20 00:29:49  elphel
*!  moved driver major/minor numbers to a single file - include/asm-cris/elphel/driver_numbers.h
*!
*!  Revision 1.2  2008/09/12 00:23:59  elphel
*!  removed cc353.c, cc353.h
*!
*!  Revision 1.4  2008/04/25 21:28:56  elphel
*!  added more functions for access from the IRQ, changed them to inline
*!
*!  Revision 1.3  2008/04/11 23:16:51  elphel
*!  removed unneeded local_irq_disable() after local_irq_save_flags()
*!
*!  Revision 1.2  2008/04/07 09:45:30  elphel
*!  removed unused variable
*!
*!  Revision 1.1  2008/04/07 09:09:07  elphel
*!  New driver to handle Exif
*!
*!
*/


//copied freom cxi2c.c - TODO:remove unneeded

#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/autoconf.h>
#include <linux/vmalloc.h>

#include <asm/system.h>
//#include <asm/svinto.h>
#include <asm/byteorder.h> // endians
#include <asm/io.h>

#include <asm/irq.h>

#include <asm/delay.h>
#include <asm/uaccess.h>

#include <asm/elphel/driver_numbers.h>
#include <asm/elphel/c313a.h>
#include <asm/elphel/exifa.h>

#include "fpgactrl.h"  // defines port_csp0_addr, port_csp4_addr 
//
//#include "x3x3.h"
//#include "cc3x3.h"


#include "exif353.h"

#define D(x)
//#define D(x) printk("%s:%d:",__FILE__,__LINE__);x


//Major
//#define X3X3_EXIF 136
//Minors
//#define X3X3_EXIF_EXIF    0 // read encoded Exif data (SEEK_END,
//#define X3X3_EXIF_META    1 // write metadata, concurently opened files. All writes atomic
// control/setup devices
//#define X3X3_EXIF_TEMPLATE 2 // write Exif template
//#define X3X3_EXIF_METADIR  3 // write metadata to Exif header translation (dir_table[MAX_EXIF_FIELDS])
// those 2 files will disable exif_enabled and exif_valid, truncate file size to file pointer on release.
//#define X3X3_EXIF_TIME     4 // write today/tomorrow date (YYYY:MM:DD) and number of seconds at today/tomorrow
                             // midnight (00:00:00) in seconds from epoch (long, startting from LSB)



#define  X3X3_EXIF_DRIVER_NAME "Elphel (R) model 353 Exif device driver"

//#define MAX_EXIF_FIELDS  256 // number of Exif tags in the header
//#define MAX_EXIF_SIZE   4096 // Exif data size 

static struct exif_dir_table_t dir_table[MAX_EXIF_FIELDS];
static int  exif_fields        = 0; // total number of the Exif fields in the header
static int  exif_template_size = 0; // size of Exif template
static int  exif_meta_size     = 0; // size of Exif meta data page
static int  exif_wp            = 1; // frame write pointer in the meta_buffer
static char exif_template[MAX_EXIF_SIZE];

static int exif_enabled = 0; // enable storing of frame meta data, enable reading Exif data
static int exif_valid  = 0; // Exif tables and buffer are valid.

static char * meta_buffer=NULL; // dynamically allocated buffer to store frame meta data.
// page 0 - tempoary storage, 1..MAX_EXIF_FRAMES - buffer

static struct exif_time_t {
  char          tomorrow_date[10]; 
  unsigned long tomorrow_sec;      
  char          today_date[10];    
  unsigned long today_sec;         
} exif_time;

static struct exif_datetime_t {
  char          datetime[20];      
  char          subsec[7];         
} now_datetime;


static int        exif_open   (struct inode *inode, struct file *filp);
static int        exif_release(struct inode *inode, struct file *filp);
static loff_t     exif_lseek  (struct file * file, loff_t offset, int orig);
static ssize_t    exif_write  (struct file * file, const char * buf, size_t count, loff_t *off);
static ssize_t    exif_read   (struct file * file, char * buf, size_t count, loff_t *off);
static int __init exif_init(void);

static struct file_operations exif_fops = {
   owner:    THIS_MODULE,
   open:     exif_open,
   release:  exif_release,
   read:     exif_read,
   write:    exif_write,
   llseek:   exif_lseek
};
ssize_t minor_file_size(int minor) { //return current file size for different minors
   switch (minor) {
     case X3X3_EXIF_TEMPLATE: return exif_template_size;
     case X3X3_EXIF_EXIF:     return exif_enabled? (exif_template_size * (MAX_EXIF_FRAMES+1)):0;
     case X3X3_EXIF_META:     return exif_meta_size;
     case X3X3_EXIF_METADIR:  return exif_fields * sizeof(struct exif_dir_table_t);
     case X3X3_EXIF_TIME:     return sizeof(struct exif_time_t);
     default:return 0;
  }
}
ssize_t minor_max_size(int minor) { //return max file size for different minors
   switch (minor) {
     case X3X3_EXIF_TEMPLATE: return MAX_EXIF_SIZE;
     case X3X3_EXIF_EXIF:     return MAX_EXIF_SIZE * (MAX_EXIF_FRAMES+1);
     case X3X3_EXIF_META:     return MAX_EXIF_SIZE;
     case X3X3_EXIF_METADIR:  return MAX_EXIF_FIELDS * sizeof(struct exif_dir_table_t);
     case X3X3_EXIF_TIME:     return sizeof(struct exif_time_t);
     default:return 0;
  }
}
void exif_invalidate(void) {
  exif_enabled = 0;
  exif_valid  = 0;
}

//reallocate meta buffer to store per-frame meta data (later output as Exif)
int exif_rebuild(int frames) {
  int i,ml;
  exif_enabled = 0;
  exif_valid  = 0;
  exif_wp     = 1;
// free buffer, if allocated
  if (meta_buffer) {
    vfree (meta_buffer);
    meta_buffer=NULL;
  }
//  calculate page size
  if (exif_fields==0) return 0; // exif_valid==0;
  for (i=0; i < exif_fields; i++) {
    ml=dir_table[i].src+dir_table[i].len;
    if (ml > exif_meta_size) exif_meta_size= ml;
  }
  if (exif_meta_size>MAX_EXIF_SIZE) {
    printk ("%s:%d: Meta frame size (0x%x) is too big (>0x%x)\n",__FILE__,__LINE__, exif_meta_size, MAX_EXIF_SIZE);
    return -1;
  }
  meta_buffer= vmalloc(exif_meta_size * (MAX_EXIF_FRAMES+1));
  if (!meta_buffer) {
    printk ("%s:%d: Failed to allocate memory (%d bytes)\n",__FILE__,__LINE__, exif_meta_size * (MAX_EXIF_FRAMES+1));
    return -1;
  }
   memset(meta_buffer, 0, exif_meta_size * (MAX_EXIF_FRAMES+1));
  exif_valid  = 1;
  return 0;
}

int exif_enable(int en) {
  int rslt;
  if (en) {
    if (!exif_valid) {
      if (((rslt=exif_rebuild(MAX_EXIF_FRAMES))) <0) return rslt;
    }
    exif_enabled = 1;
  } else {
    exif_enabled = 0;
  }
  return 0;
}
int dir_find_tag (unsigned long tag) { //find location of the tag field in meta page 
  int indx;
//  for (indx=0; indx < exif_fields; indx++) if (dir_table[indx].ltag==tag) return indx;
  for (indx=0; indx < exif_fields; indx++) if (dir_table[indx].ltag==tag) return (int) dir_table[indx].src;
  return -1;
}

inline void write_meta_raw_irq(char * data, int offset, int len) { //write data to meta, called from IRQ
  if (exif_enabled) memcpy(&meta_buffer[ offset], data, len);
}

inline int write_meta_irq(char * data, int * indx,  unsigned long ltag, int len) { //write data to meta, called from IRQ(len==0 => use field length)
  int i;
  if (!exif_enabled) return 0;
  if (indx && (dir_table[* indx].ltag==ltag)) i=*indx;
  else {
    for (i=0; i<exif_fields; i++) if (dir_table[i].ltag==ltag) break;
    if (i>=exif_fields) return -1; //ltag not found
  }
  if (len==0) len=dir_table[i].len;
  memcpy(&meta_buffer[dir_table[i].src], data, len);
  if (indx)  * indx=i;
  return dir_table[i].src;
}

inline void putlong_meta_raw_irq(unsigned long data, int offset) { //write data to meta (4 bytes, big endian), called from IRQ
  unsigned long bedata=__cpu_to_be32(data);
  if (exif_enabled) {
    memcpy(&meta_buffer[ offset], &bedata, 4);
  }
}

inline int putlong_meta_irq(unsigned long data, int * indx,  unsigned long ltag) { //write data to meta (4 bytes, big endian), from IRQ
  int i;
  unsigned long bedata=__cpu_to_be32(data);
  if (!exif_enabled) return -10;
  if (indx && (dir_table[* indx].ltag==ltag)) i=*indx;
  else {
    for (i=0; i<exif_fields; i++) if (dir_table[i].ltag==ltag) break;
    if (i>=exif_fields) return -1; //ltag not found
  }
  memcpy(&meta_buffer[dir_table[i].src], &bedata, 4);
  if (indx)  * indx=i;
  return dir_table[i].src;
}



void write_meta_raw(char * data, int offset, int len) { //write data to meta, called from outside IRQ (atomic)
  unsigned long flags;
  if (exif_enabled) {
    local_irq_save(flags);
    //local_irq_disable();
    memcpy(&meta_buffer[ offset], data, len);
    local_irq_restore(flags);
  }
}
int write_meta(char * data, int * indx,  unsigned long ltag, int len) { //write data to meta, from outside IRQ (atomic) (len==0 => use field length)
  int i;
  unsigned long flags;
  if (!exif_enabled) return 0;
  if (indx && (dir_table[* indx].ltag==ltag)) i=*indx;
  else {
    for (i=0; i<exif_fields; i++) if (dir_table[i].ltag==ltag) break;
    if (i>=exif_fields) return -1; //ltag not found
  }
  if (len==0) len=dir_table[i].len;
  local_irq_save(flags);
  //local_irq_disable();
  memcpy(&meta_buffer[dir_table[i].src], data, len);
  local_irq_restore(flags);
  if (indx)  * indx=i;
  return dir_table[i].src;
}

void putlong_meta_raw(unsigned long data, int offset) { //write data to meta (4 bytes, big endian), called from outside IRQ (atomic)
  unsigned long flags;
  unsigned long bedata=__cpu_to_be32(data);
  if (exif_enabled) {
    local_irq_save(flags);
    //local_irq_disable();
    memcpy(&meta_buffer[ offset], &bedata, 4);
    local_irq_restore(flags);
  }
}

int putlong_meta(unsigned long data, int * indx,  unsigned long ltag) { //write data to meta (4 bytes, big endian), from outside IRQ (atomic)
  int i;
  unsigned long flags;
  unsigned long bedata=__cpu_to_be32(data);
  if (!exif_enabled) return -10;
  if (indx && (dir_table[* indx].ltag==ltag)) i=*indx;
  else {
    for (i=0; i<exif_fields; i++) if (dir_table[i].ltag==ltag) break;
    if (i>=exif_fields) return -1; //ltag not found
  }
  local_irq_save(flags);
  //local_irq_disable();
  memcpy(&meta_buffer[dir_table[i].src], &bedata, 4);
  local_irq_restore(flags);
  if (indx)  * indx=i;
  return dir_table[i].src;
}

/*

   exp_bigendian=__cpu_to_be32((int)fp->exposure);

static struct exif_time_t {
  char          tomorrow_date[10]; //!"YYYY:MM:DD"
  unsigned long tomorrow_sec;      //!seconds from epoch tomorrow at 00:00
  char          today_date[10];    //!"YYYY:MM:DD"
  unsigned long today_sec;         //!seconds from epoch today at 00:00
} exif_time;

static struct exif_datetime_t {
  char          datetime[20];      //!"YYYY:MM:DD HH:MM:SS\0"
  char          subsec[7];         //!ASCII microseconds (0-padded), ."\0"
} now_datetime;
*/
// The next function is normally called from the interrupt service routine
// Encode time (epoch sec, usec) into static buffer, return pointer to the buffer 
// Uses struct exif_time that should be updater from the user space (once a day),
// calculates date/time ignoring leap seconds if not updated in time
char * encode_time(unsigned long sec, unsigned long usec) {
  unsigned long s,d,m,y,y4,lp,h;
  if (((sec-exif_time.today_sec)>86400) || (sec < exif_time.today_sec)) {// today's time is not valid, try tomorrow:
    memcpy(&exif_time.today_date[0],&exif_time.tomorrow_date[0],sizeof(exif_time.today_date)+sizeof(exif_time.today_sec));
    if (((sec-exif_time.today_sec)>86400) || (sec < exif_time.today_sec)) {// today's time is _still_ not valid, has to do it itself :-(
      d=sec/86400;
      s=d*86400;
      y4=d/1461; // number of 4-year periods
      d-=1461*y4; //days after 1970, 1974, ...
      y=(d- ((d>=1095)?1:0))/365;
      d-=y*365-((y>2)?1:0);
      lp=(y==2);
      y+=4*y4+1970;
      if ((!lp) && (d>58)) d++;
//      d+=(lp && (d>58))?1:0;
      D(printk("d=%ld, y=%ld, y4=%ld, lp=%ld\n",d, y, y4, lp));
      if (d>181) {
        if (d>273) {
          if (d>304) {
            if (d>334) {m=12;d-=334;} // December
            else       {m=11;d-=304;} // November
          } else       {m=10;d-=273;} // October
        } else {
          if (d>212) {
            if (d>243) {m= 9;d-=243;} // September
            else       {m= 8;d-=212;} // August
          } else       {m= 7;d-=181;} // July
        }
      } else {
        if (d>90) {
          if (d>120) {
            if (d>151) {m=6; d-=151;} // June
            else       {m=5; d-=120;} // May
          } else       {m=4; d-= 90;} // April
        } else {
          if (d>30) {
            if (d>59)  {m=3; d-= 59;} // March
            else       {m=2; d-= 30;} // February
          } else       {m=1; d++;   } // January
        }
      }
      D(printk("d=%ld, y=%ld, y4=%ld\n",d, y, y4));
      sprintf(exif_time.today_date,"%04ld:%02ld:%02ld",y,m,d);
      exif_time.today_sec=s;
    }
    memcpy (&now_datetime.datetime[0],exif_time.today_date,10);
    now_datetime.datetime[10]=' ';
    now_datetime.datetime[19]='\0';
    now_datetime.subsec[6]='\0';
  }
// now we have valid exif_time.today_date, exif_time.today_sec;
  s=sec-exif_time.today_sec;
  h= s/3600;
  s-= 3600*h;
  m=  s/60;
  s-= 60*m;
  sprintf(&now_datetime.datetime[11],"%02ld:%02ld:%02ld",h,m,s);
  sprintf(&now_datetime.subsec[0],"%06ld",usec);
  return &now_datetime.datetime[0];
}

int store_meta(void) { //called from IRQ service - put current metadata to meta_buffer, return page index
  if (!exif_enabled) return 0;
  int retval=exif_wp;
  memcpy(&meta_buffer[exif_wp*exif_meta_size],meta_buffer,exif_meta_size);
  exif_wp++;
  if (exif_wp > MAX_EXIF_FRAMES) exif_wp=1;
  return retval;
}


static int exif_open(struct inode *inode, struct file *filp) {
   int p = MINOR(inode->i_rdev);
   int * pd= (int *) &(filp->private_data);
   switch (p) {
     case X3X3_EXIF_EXIF:
     case X3X3_EXIF_META:
     case X3X3_EXIF_TEMPLATE:
     case X3X3_EXIF_METADIR:
     case X3X3_EXIF_TIME:
       break;
     default:return -EINVAL;
  }

   D(printk("exif_open, minor=%d\n",p));
   inode->i_size=minor_file_size(p);
   pd[0]=p; // just a minor number
   return 0;
}


static int exif_release(struct inode *inode, struct file *filp){
   int p = MINOR(inode->i_rdev);
   int * pd= (int *) &(filp->private_data);
   switch (p) {
     case X3X3_EXIF_EXIF:
      break;
     case X3X3_EXIF_META:
      break;
     case X3X3_EXIF_TEMPLATE:
      break;
     case X3X3_EXIF_METADIR:
      break;
     case X3X3_EXIF_TIME:
       break;
     default:return -EINVAL;
   }

   D(printk("exif_open, minor=%d\n",p));
   inode->i_size=minor_file_size(p);
   pd[0]=p; // just a minor number
   return 0;
}


static loff_t exif_lseek  (struct file * file, loff_t offset, int orig) {
   int p=(int)file->private_data;
   int thissize=minor_file_size(p);
   int maxsize=minor_max_size(p);
   int fp;
   switch (orig) {
   case SEEK_SET:
      file->f_pos = offset;
      break;
   case SEEK_CUR:
      file->f_pos += offset;
      break;
   case SEEK_END:
      if (offset<=0) {
        file->f_pos = thissize + offset;
      } else {

        switch (p) {
          case X3X3_EXIF_TEMPLATE: //enable/disable
            switch (offset) {
              case EXIF_LSEEK_DISABLE:
                exif_enable(0);
                break;
              case EXIF_LSEEK_ENABLE:
                if (exif_enable(1)<0) return -EOVERFLOW; //TODO: change code
                break;
              case EXIF_LSEEK_INVALIDATE:
                exif_invalidate();
                break;
              case EXIF_LSEEK_REBUILD:
                if (exif_rebuild(MAX_EXIF_FRAMES)<0) return -EOVERFLOW; //TODO: change code
                break;
              default:return -EINVAL;
            }
            break;
          case X3X3_EXIF_EXIF: // select page in the buffer
            if (offset > MAX_EXIF_FRAMES) return -EOVERFLOW; //larger than buffer
//            file->f_pos=exif_meta_size * offset;
            file->f_pos=exif_template_size * offset;

            break;
          case X3X3_EXIF_META: // iterate
            fp= dir_find_tag (offset);
            if (fp < 0) return -EOVERFLOW; // tag is not in the directory
            file->f_pos=fp;
            break;
          case X3X3_EXIF_METADIR: 
               file->f_pos=offset*sizeof(struct exif_dir_table_t);
            break;
          case X3X3_EXIF_TIME:
            switch (offset) {
              case EXIF_LSEEK_TOMORROW_DATE:
               file->f_pos=exif_time.tomorrow_date - ((char *) &exif_time);
               break;
              case EXIF_LSEEK_TOMORROW_SEC:
               file->f_pos=((char *) &exif_time.tomorrow_sec) - ((char *) &exif_time);
               break;
              case EXIF_LSEEK_TODAY_DATE:
               file->f_pos=exif_time.today_date - ((char *) &exif_time);
               break;
              case EXIF_LSEEK_TODAY_SEC:
               file->f_pos=((char *) &exif_time.today_sec) - ((char *) &exif_time);
               break;
              default:return -EINVAL;
            }
            break;
          default:return -EINVAL;
        }
      }
      break;
   default:
      return -EINVAL;
   }
   /* truncate position */
   if (file->f_pos < 0) {
      file->f_pos = 0;
      return (-EOVERFLOW);
   }

   if (file->f_pos > maxsize) {
      file->f_pos = maxsize;
      return (-EOVERFLOW);
   }
   return (file->f_pos);
}


static ssize_t    exif_write  (struct file * file, const char * buf, size_t count, loff_t *off) {
  int p=(int)file->private_data;
//  int thissize=minor_file_size(p);
  int maxsize=minor_max_size(p);
  char * cp;
  char tmp[MAX_EXIF_SIZE]; 
  unsigned long flags;
  int disabled_err=0;
  if ((*off+count)>maxsize) {
    printk ("%s:%d: Data (0x%x) does not fit into 0x%x bytes\n",__FILE__,__LINE__, (int) (*off+count), maxsize);
    return -EOVERFLOW;
  }
  switch (p) {
     case X3X3_EXIF_TEMPLATE:
       exif_invalidate();
       if (copy_from_user(&exif_template[*off], buf, count)) return -EFAULT;
       exif_template_size=*off+count;
       break;
     case X3X3_EXIF_METADIR:
       exif_invalidate();
       cp= (char *) &dir_table;
       if (copy_from_user(&cp[*off], buf, count)) return -EFAULT;
       exif_fields=(*off+count)/sizeof(struct exif_dir_table_t);
       break;
     case X3X3_EXIF_TIME: //write date/time first, then - midnight seconds
       cp= (char *) &exif_time;
       if (copy_from_user(&cp[*off], buf, count)) return -EFAULT;
       break;
     case X3X3_EXIF_META:
       if (copy_from_user(tmp, buf, count)) return -EFAULT;
       local_irq_save(flags);
       //local_irq_disable();
       if (exif_enabled) memcpy(&meta_buffer[*off], tmp, count);
       else disabled_err=1;
       local_irq_restore(flags);
       if (disabled_err) {
         D(printk("tried to write meta while disabled\n"));
         count=0;
       }
       break;
     case X3X3_EXIF_EXIF:
       return -EINVAL; // no writing - read only
       break;
     default:return -EINVAL;
  }
  *off+=count;
  D(printk("count= 0x%x, pos= 0x%x\n", (int) count, (int)*off));
  return count;
}


static ssize_t    exif_read   (struct file * file, char * buf, size_t count, loff_t *off) {
  int p=(int)file->private_data;
  int thissize=minor_file_size(p);
//  int maxsize=minor_max_size(p);
  char * cp, * metap;
  int start_p, page_p,i;
  
  char tmp[MAX_EXIF_SIZE]; 
/*
  Does not work with PHP - always read 8192 bytes
  if ((*off+count)>maxsize) {
    printk ("%s:%d: Data (0x%x) does not fit into 0x%x bytes\n",__FILE__,__LINE__, (int) (*off+count), maxsize);
    return -EOVERFLOW;
  }
*/
  if (*off > thissize) {
    return 0; // nothing to read
  }
  if ((*off + count) > thissize) {
    count=thissize-*off;
  }

  switch (p) {
     case X3X3_EXIF_TEMPLATE:
       if (copy_to_user(buf,  &exif_template[*off], count)) return -EFAULT;
       break;
     case X3X3_EXIF_METADIR:
       cp= (char *) &dir_table;
       if (copy_to_user(buf,  &cp[*off], count)) return -EFAULT;
       break;
     case X3X3_EXIF_TIME:
       cp= (char *) &exif_time;
       if (copy_to_user(buf,  &cp[*off], count)) return -EFAULT;
       break;
     case X3X3_EXIF_META:
       if (!exif_enabled) return 0;
       if (copy_to_user(buf,  &meta_buffer[*off], count)) return -EFAULT;
       break;
     case X3X3_EXIF_EXIF: // generates exif data by merging exif_template with the selected meta_buffer page
//will truncate by the end of current page
       if (!exif_enabled) return 0;
       i=((int) *off) / exif_template_size;
  D(printk("count= 0x%x, *off= 0x%x, i=0x%x, exif_template_size=0x%x\n", (int) count, (int) *off, (int) i, (int) exif_template_size));
//arch/cris/arch-v32/drivers/elphel/exif353.c:590:count= 0x2000, *off= 0x410, i=0x82, exif_template_size=0x208
       start_p=i*exif_template_size;
       page_p= *off - start_p;
  D(printk("count= 0x%x, pos= 0x%x, start_p=0x%x, page_p=0x%x, i=0x%x, exif_template_size=0x%x\n", (int) count, (int) *off, (int)start_p, (int)page_p,(int) i, (int) exif_template_size));
//arch/cris/arch-v32/drivers/elphel/exif353.c:591:count= 0x2000, pos= 0x410, start_p=0x10810, page_p=0xfffefc00, i=0x82, exif_template_size=0x208

       metap= &meta_buffer[i*exif_meta_size]; // pointer to the start of the selected page in frame meta_buffer
       if ((page_p+count) > exif_template_size) count=exif_template_size-page_p;
       memcpy(tmp,exif_template, exif_template_size);
  D(printk("count= 0x%x, pos= 0x%x, start_p=0x%x, page_p=0x%x\n", (int) count, (int) *off, (int)start_p, (int)page_p));
       for (i=0;i<exif_fields;i++){
         memcpy(&tmp[dir_table[i].dst],&metap[dir_table[i].src], dir_table[i].len);
       }
       if (copy_to_user(buf,  &tmp[page_p], count)) return -EFAULT;
       break;
     default:return -EINVAL;
  }
  *off+=count;
  D(printk("count= 0x%x, pos= 0x%x\n", (int) count, (int)*off));
  return count;
}



static int __init exif_init(void) {
   int res;
   res = register_chrdev(X3X3_EXIF_MAJOR, "Exif", &exif_fops);
   if(res < 0) {
     printk(KERN_ERR "\nexif_init: couldn't get a major number  %d.\n",X3X3_EXIF_MAJOR);
     return res;
   }
   printk(X3X3_EXIF_DRIVER_NAME" - %d\n",X3X3_EXIF_MAJOR);
   return 0;
}

module_init(exif_init);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Andrey Filippov <andrey@elphel.com>.");
MODULE_DESCRIPTION(X3X3_EXIF_DRIVER_NAME);

---