limit hardware lineart up to 600 dpi for gl847 scanners

- due to interleaving at bit level and uneven sub sensor length,
  hardware lineart is almost unworkable when resolution exceeds 600.

backend/genesys.c

@@ -4544,7 +4544,7 @@ genesys_fill_segmented_buffer (Genesys_Device * dev, uint8_t *work_buffer_dst, s
                             {
                                   work_buffer_dst[count+n] = 0;
                             }
-                          /* interleaving is a bit level */
+                          /* interleaving is at bit level */
                           for(i=0;i<8;i++)
                             {
                               k=count+(i*dev->segnb)/8;
@@ -5289,6 +5289,7 @@ calc_parameters (Genesys_Scanner * s)
    * or when xres is doubled to match yres */
   if (s->dev->settings.xres >= 1200
       && (    s->dev->model->asic_type == GENESYS_GL124 
+           || s->dev->model->asic_type == GENESYS_GL847
            || s->dev->current_setup.xres < s->dev->current_setup.yres
          )
      )
@@ -5359,11 +5360,22 @@ calc_parameters (Genesys_Scanner * s)
    &&s->dev->settings.scan_mode == SCAN_MODE_LINEART)
    {
       s->dev->settings.dynamic_lineart = SANE_TRUE;
-      /* threshold curve for dynamic ratserization */
-      if(s->dev->settings.dynamic_lineart==SANE_TRUE)
-          s->dev->settings.threshold_curve=s->val[OPT_THRESHOLD_CURVE].w;
    }
 
+  /* hardware lineart works only when we don't have interleave data
+   * for GL847 scanners, ie up to 600 DPI, then we have to rely on
+   * dynamic_lineart */
+  if(s->dev->settings.xres > 600 
+     && s->dev->model->asic_type==GENESYS_GL847
+     && s->dev->settings.scan_mode == SCAN_MODE_LINEART)
+   {
+      s->dev->settings.dynamic_lineart = SANE_TRUE;
+   }
+  
+  
+  /* threshold curve for dynamic rasterization */
+  s->dev->settings.threshold_curve=s->val[OPT_THRESHOLD_CURVE].w;
+
   /* some digital processing requires the whole picture to be buffered */
   /* no digital processing takes place when doing preview, or when bit depth is
    * higher than 8 bits */

backend/genesys_gl847.c

@@ -1329,18 +1329,12 @@ gl847_init_optical_regs_scan (Genesys_Device * dev,
 	}*/
     }
 
-  sanei_genesys_set_double(reg,REG_DPISET,dpiset);
-  DBG (DBG_io2, "%s: dpiset used=%d\n", __FUNCTION__, dpiset);
-
-  sanei_genesys_set_double(reg,REG_STRPIXEL,startx);
-  sanei_genesys_set_double(reg,REG_ENDPIXEL,endx);
-
   /* words(16bit) before gamma, conversion to 8 bit or lineart*/
   words_per_line = (used_pixels * dpiset) / dpihw;
   bytes=depth/8;
   if (depth == 1)
     {
-      words_per_line = (words_per_line >> 3) + ((words_per_line & 7) ? 1 : 0);
+      words_per_line = (words_per_line+7)/8 ;
       dev->len = (dev->len >> 3) + ((dev->len & 7) ? 1 : 0);
       dev->dist = (dev->dist >> 3) + ((dev->dist & 7) ? 1 : 0);
     }
@@ -1356,6 +1350,14 @@ gl847_init_optical_regs_scan (Genesys_Device * dev,
   dev->segnb=segnb;
   dev->line_interp = 0;
 
+  sanei_genesys_set_double(reg,REG_DPISET,dpiset);
+  DBG (DBG_io2, "%s: dpiset used=%d\n", __FUNCTION__, dpiset);
+
+  sanei_genesys_set_double(reg,REG_STRPIXEL,startx);
+  sanei_genesys_set_double(reg,REG_ENDPIXEL,endx);
+  DBG (DBG_io2, "%s: startx=%d\n", __FUNCTION__, startx);
+  DBG (DBG_io2, "%s: endx  =%d\n", __FUNCTION__, endx);
+
   DBG (DBG_io2, "%s: used_pixels=%d\n", __FUNCTION__, used_pixels);
   DBG (DBG_io2, "%s: pixels     =%d\n", __FUNCTION__, pixels);
   DBG (DBG_io2, "%s: depth      =%d\n", __FUNCTION__, depth);