Signed-off-by: Sean Young <sean@xxxxxxxx>
---
drivers/media/rc/iguanair.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/drivers/media/rc/iguanair.c b/drivers/media/rc/iguanair.c
index fdae05c..99a3a5a 100644
--- a/drivers/media/rc/iguanair.c
+++ b/drivers/media/rc/iguanair.c
@@ -286,10 +286,10 @@ static int iguanair_receiver(struct iguanair *ir, bool enable)
}
/*
- * The iguana ir creates the carrier by busy spinning after each pulse or
- * space. This is counted in CPU cycles, with the CPU running at 24MHz. It is
+ * The iguanair creates the carrier by busy spinning after each half period.
+ * This is counted in CPU cycles, with the CPU running at 24MHz. It is
* broken down into 7-cycles and 4-cyles delays, with a preference for
- * 4-cycle delays.
+ * 4-cycle delays, minus the overhead of the loop itself (cycle_overhead).
*/
static int iguanair_set_tx_carrier(struct rc_dev *dev, uint32_t carrier)
{
@@ -316,7 +316,14 @@ static int iguanair_set_tx_carrier(struct rc_dev *dev, uint32_t carrier)
sevens = (4 - cycles) & 3;
fours = (cycles - sevens * 7) / 4;
- /* magic happens here */
+ /*
+ * The firmware interprets these values as a relative offset
+ * for a branch. Immediately following the branches, there
+ * 4 instructions of 7 cycles (2 bytes each) and 110
+ * instructions of 4 cycles (1 byte each). A relative branch
+ * of 0 will execute all of them, branch further for less
+ * cycle burning.
+ */
ir->packet->busy7 = (4 - sevens) * 2;
ir->packet->busy4 = 110 - fours;
}
--
1.8.4.2
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