spelling fixes for cardscan backend

backend/cardscan.c

@@ -167,7 +167,7 @@ many times {
 
 14/94 and 22/a2
 
-########### discarge capacitor? ###########
+########### discharge capacitor? ###########
 four times {
 >> 21 02 00 0a 00
 << a1 00 02 00 0a 00
@@ -879,7 +879,7 @@ sane_control_option (SANE_Handle handle, SANE_Int option,
       DBG (20, "sane_control_option: set value for '%s' (%d)\n", s->opt[option].name,option);
 
       if ( s->started ) {
-        DBG (5, "sane_control_option: cant set, device busy\n");
+        DBG (5, "sane_control_option: can't set, device busy\n");
         return SANE_STATUS_DEVICE_BUSY;
       }
 
@@ -1366,7 +1366,7 @@ read_from_scanner_color(struct scanner *s)
  * handle h is a valid handle) but usually affects long-running
  * operations only (such as image is acquisition). It is safe to call
  * this function asynchronously (e.g., from within a signal handler).
- * It is important to note that completion of this operaton does not
+ * It is important to note that completion of this operation does not
  * imply that the currently pending operation has been cancelled. It
  * only guarantees that cancellation has been initiated. Cancellation
  * completes only when the cancelled call returns (typically with a

doc/sane-cardscan.man

@@ -37,7 +37,7 @@ Scanners can be specified in the configuration file in 2 ways:
 .PP
 "usb 0x04c5 0x1042" (or other vendor/product ids)
 .RS
-Requests backend to search all usb busses in the system for a device
+Requests backend to search all usb buses in the system for a device
 which uses that vendor and product id. The device will then be queried
 to determine if it is a cardscan scanner.
 .RE