staging: comedi: multiq3: document the encoder chip commands

Add some comments to document the commands that are sent to the
encoder chips.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/comedi/drivers/multiq3.c b/drivers/staging/comedi/drivers/multiq3.c
index dac1879..02d41fc 100644 (file)
--- a/drivers/staging/comedi/drivers/multiq3.c
+++ b/drivers/staging/comedi/drivers/multiq3.c
@@ -65,17 +65,17 @@
 #define MULTIQ3_ENC_CTRL_REG           0x0e
 
 /*
- * flags for encoder control
+ * Encoder chip commands (from the programming manual)
  */
-#define MULTIQ3_CLOCK_DATA      0x00
-#define MULTIQ3_CLOCK_SETUP     0x18
-#define MULTIQ3_INPUT_SETUP     0x41
-#define MULTIQ3_QUAD_X4         0x38
-#define MULTIQ3_BP_RESET        0x01
-#define MULTIQ3_CNTR_RESET      0x02
-#define MULTIQ3_TRSFRPR_CTR     0x08
-#define MULTIQ3_TRSFRCNTR_OL    0x10
-#define MULTIQ3_EFLAG_RESET     0x06
+#define MULTIQ3_CLOCK_DATA             0x00    /* FCK frequency divider */
+#define MULTIQ3_CLOCK_SETUP            0x18    /* xfer PR0 to PSC */
+#define MULTIQ3_INPUT_SETUP            0x41    /* enable inputs A and B */
+#define MULTIQ3_QUAD_X4                        0x38    /* quadrature */
+#define MULTIQ3_BP_RESET               0x01    /* reset byte pointer */
+#define MULTIQ3_CNTR_RESET             0x02    /* reset counter */
+#define MULTIQ3_TRSFRPR_CTR            0x08    /* xfre preset reg to counter */
+#define MULTIQ3_TRSFRCNTR_OL           0x10    /* xfer CNTR to OL (x and y) */
+#define MULTIQ3_EFLAG_RESET            0x06    /* reset E bit of flag reg */
 
 #define MULTIQ3_TIMEOUT 30