added rejection of count == 1 for mode 3, added i8254_read() function

diff --git a/comedi/drivers/8253.h b/comedi/drivers/8253.h
index 3892467a2f1ac31f9a31049e15624ff41d8dc1cd..43b0e153329fad0adc6be3f2c43f2b7b5143fbbe 100644 (file)
--- a/comedi/drivers/8253.h
+++ b/comedi/drivers/8253.h
@@ -199,25 +199,34 @@ static inline void i8253_cascade_ns_to_timer_2div(int i8253_osc_base,
 }
 
 #ifndef CMDTEST
-/* Programs 8254 counter chip.  It should also work for the 8253.
+/* i8254_load programs 8254 counter chip.  It should also work for the 8253.
  * base_address is the lowest io address for the chip (the address of counter 0).
  * counter_number is the counter you want to load (0,1 or 2)
  * count is the number to load into the counter.
+ *
  * You probably want to use mode 2.
+ *
  * Use i8254_mm_load() if you board uses memory-mapped io, it is
  * the same as i8254_load() except it uses writeb() instead of outb().
+ *
+ * Neither i8254_load() or i8254_read() do their loading/reading
+ * atomically.  The 16 bit read/writes are performed with two successive
+ * 8 bit read/writes.  So if two parts of your driver do a load/read on
+ * the same counter, it may be necessary to protect these functions
+ * with a spinlock.
+ *
  * FMH
  */
 static inline int i8254_load(unsigned int base_address,
        unsigned int counter_number, unsigned int count, unsigned int mode)
 {
-       unsigned char byte;
+       unsigned int byte;
        static const int counter_control = 3;
 
        if(counter_number > 2) return -1;
        if(count > 0xffff) return -1;
        if(mode > 5) return -1;
-       if(mode == 2 && count == 1) return -1;
+       if((mode == 2 || mode == 3) && count == 1) return -1;
 
        byte = counter_number << 6;
        byte |= 0x30;   // load low then high byte
@@ -234,13 +243,13 @@ static inline int i8254_load(unsigned int base_address,
 static inline int i8254_mm_load(unsigned int base_address,
        unsigned int counter_number, unsigned int count, unsigned int mode)
 {
-       unsigned char byte;
+       unsigned int byte;
        static const int counter_control = 3;
 
        if(counter_number > 2) return -1;
        if(count > 0xffff) return -1;
        if(mode > 5) return -1;
-       if(mode == 2 && count == 1) return -1;
+       if((mode == 2 || mode == 3) && count == 1) return -1;
 
        byte = counter_number << 6;
        byte |= 0x30;   // load low then high byte
@@ -253,6 +262,27 @@ static inline int i8254_mm_load(unsigned int base_address,
 
        return 0;
 }
+
+/* Returns 16 bit counter value, should work for 8253 also.*/
+static inline int i8254_read(unsigned int base_address, unsigned int counter_number)
+{
+       unsigned int byte;
+       int ret;
+       static const int counter_control = 3;
+
+       if(counter_number > 2) return -1;
+
+       // latch counter
+       byte = counter_number << 6;
+       outb(byte, base_address + counter_control);
+
+       // read lsb
+       ret = inb(base_address + counter_number);
+       // read msb
+       ret += inb(base_address + counter_number) << 8;
+
+       return ret;
+}
 #endif
 
 #endif