V4L/DVB: ir-rc5-decoder: fix state machine

Reimplement the RC-5 decoder state machine. Code is now clear, and works
properly. It is also simpler than the previous implementations.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 52 insertions, 109 deletions

diff --git a/drivers/media/IR/ir-rc5-decoder.c b/drivers/media/IR/ir-rc5-decoder.c
index 4fb3ce410e24..a62277b625a8 100644
--- a/drivers/media/IR/ir-rc5-decoder.c
+++ b/drivers/media/IR/ir-rc5-decoder.c
@@ -15,19 +15,17 @@
 /*
  * This code only handles 14 bits RC-5 protocols. There are other variants
  * that use a different number of bits. This is currently unsupported
+ * It considers a carrier of 36 kHz, with a total of 14 bits, where
+ * the first two bits are start bits, and a third one is a filing bit
  */
 
 #include <media/ir-core.h>
 
-#define RC5_NBITS               14
-#define RC5_HALFBIT             888888 /* ns */
-#define RC5_BIT                 (RC5_HALFBIT * 2)
-#define RC5_DURATION            (RC5_BIT * RC5_NBITS)
-
-#define is_rc5_halfbit(nsec) ((ev->delta.tv_nsec >= RC5_HALFBIT / 2) &&    \
-                      (ev->delta.tv_nsec < RC5_HALFBIT + RC5_HALFBIT / 2))
+static unsigned int ir_rc5_remote_gap = 888888;
 
-#define n_half(nsec) ((ev->delta.tv_nsec + RC5_HALFBIT / 2) / RC5_HALFBIT)
+#define RC5_NBITS               14
+#define RC5_BIT                 (ir_rc5_remote_gap * 2)
+#define RC5_DURATION            (ir_rc5_remote_gap * RC5_NBITS)
 
 /* Used to register rc5_decoder clients */
 static LIST_HEAD(decoder_list);
@@ -35,19 +33,8 @@ static spinlock_t decoder_lock;
 
 enum rc5_state {
         STATE_INACTIVE,
-        STATE_START2_SPACE,
-        STATE_START2_MARK,
         STATE_MARKSPACE,
-        STATE_TRAILER_MARK,
-};
-
-static char *st_name[] = {
-        "Inactive",
-        "start2 sapce",
-        "start2 mark",
-        "mark",
-        "space",
-        "trailer"
+        STATE_TRAILER,
 };
 
 struct rc5_code {
@@ -63,8 +50,7 @@ struct decoder_data {
         /* State machine control */
         enum rc5_state          state;
         struct rc5_code         rc5_code;
-        unsigned                n_half;
-        unsigned                count;
+        unsigned                code, elapsed, last_bit, last_code;
 };
 
 
@@ -147,7 +133,7 @@ static int ir_rc5_decode(struct input_dev *input_dev,
 {
         struct decoder_data *data;
         struct ir_input_dev *ir_dev = input_get_drvdata(input_dev);
-        int bit, last_bit, n_half;
+        int is_pulse, scancode, delta, toggle;
 
         data = get_decoder_data(ir_dev);
         if (!data)
@@ -156,122 +142,79 @@ static int ir_rc5_decode(struct input_dev *input_dev,
         if (!data->enabled)
                 return 0;
 
-        /* Except for the initial event, what matters is the previous bit */
-        bit = (ev->type & IR_PULSE) ? 1 : 0;
-
-        last_bit = !bit;
+        delta = DIV_ROUND_CLOSEST(ev->delta.tv_nsec, ir_rc5_remote_gap);
 
-        /* Discards spurious space last_bits when inactive */
+        /* The duration time refers to the last bit time */
+        is_pulse = (ev->type & IR_PULSE) ? 1 : 0;
 
         /* Very long delays are considered as start events */
-        if (ev->delta.tv_nsec > RC5_DURATION + RC5_HALFBIT / 2)
-                data->state = STATE_INACTIVE;
-
-        if (ev->type & IR_START_EVENT)
+        if (delta > RC5_DURATION || (ev->type & IR_START_EVENT))
                 data->state = STATE_INACTIVE;
 
         switch (data->state) {
         case STATE_INACTIVE:
-IR_dprintk(1, "currently inative. Received bit (%s) @%luus\n",
-        last_bit ? "pulse" : "space",
-        (ev->delta.tv_nsec + 500) / 1000);
+        IR_dprintk(2, "currently inative. Start bit (%s) @%uus\n",
+                   is_pulse ? "pulse" : "space",
+                   (unsigned)(ev->delta.tv_nsec + 500) / 1000);
 
                 /* Discards the initial start space */
-                if (bit)
-                        return 0;
-                data->count = 0;
-                data->n_half = 0;
-                memset (&data->rc5_code, 0, sizeof(data->rc5_code));
-
-                data->state = STATE_START2_SPACE;
-                return 0;
-        case STATE_START2_SPACE:
-                if (last_bit)
-                        goto err;
-                if (!is_rc5_halfbit(ev->delta.tv_nsec))
-                        goto err;
-                data->state = STATE_START2_MARK;
-                return 0;
-        case STATE_START2_MARK:
-                if (!last_bit)
+                if (!is_pulse)
                         goto err;
-
-                if (!is_rc5_halfbit(ev->delta.tv_nsec))
-                        goto err;
-
+                data->code = 1;
+                data->last_bit = 1;
+                data->elapsed = 0;
+                memset(&data->rc5_code, 0, sizeof(data->rc5_code));
                 data->state = STATE_MARKSPACE;
                 return 0;
         case STATE_MARKSPACE:
-                n_half = n_half(ev->delta.tv_nsec);
-                if (n_half < 1 || n_half > 3) {
-                        IR_dprintk(1, "Decode failed at %d-th bit (%s) @%luus\n",
-                                data->count,
-                                last_bit ? "pulse" : "space",
-                                (ev->delta.tv_nsec + 500) / 1000);
-printk("%d halves\n", n_half);
-                        goto err2;
-                }
-                data->n_half += n_half;
+                if (delta != 1)
+                        data->last_bit = data->last_bit ? 0 : 1;
 
-                if (!last_bit)
-                        return 0;
+                data->elapsed += delta;
 
-                /* Got one complete mark/space cycle */
+                if ((data->elapsed % 2) == 1)
+                        return 0;
 
-                bit = ((data->count + 1) * 2)/ data->n_half;
+                data->code <<= 1;
+                data->code |= data->last_bit;
 
-printk("%d halves, %d bits\n", n_half, bit);
+                /* Fill the 2 unused bits at the command with 0 */
+                if (data->elapsed / 2 == 6)
+                        data->code <<= 2;
 
-#if 1 /* SANITY check - while testing the decoder */
-                if (bit > 1) {
-                        IR_dprintk(1, "Decoder HAS failed at %d-th bit (%s) @%luus\n",
-                                data->count,
-                                last_bit ? "pulse" : "space",
-                                (ev->delta.tv_nsec + 500) / 1000);
+                if (data->elapsed >= (RC5_NBITS - 1) * 2) {
+                        scancode = data->code;
 
-                        goto err2;
-                }
-#endif
-                /* Ok, we've got a valid bit. proccess it */
-                if (bit) {
-                        int shift = data->count;
-
-                        /*
-                         * RC-5 transmit bytes on this temporal order:
-                         * address | not address | command | not command
-                         */
-                        if (shift < 8) {
-                                data->rc5_code.address |= 1 << shift;
-                        } else {
-                                data->rc5_code.command |= 1 << (shift - 8);
+                        /* Check for the start bits */
+                        if ((scancode & 0xc000) != 0xc000) {
+                                IR_dprintk(1, "Code 0x%04x doesn't have two start bits. It is not RC-5\n", scancode);
+                                goto err;
                         }
-                }
-                IR_dprintk(1, "RC-5: bit #%d: %d (%d)\n",
-                                data->count, bit, data->n_half);
-                if (++data->count >= RC5_NBITS) {
-                        u32 scancode;
-                        scancode = data->rc5_code.address << 8 |
-                                        data->rc5_code.command;
-                        IR_dprintk(1, "RC-5 scancode 0x%04x\n", scancode);
 
-                        ir_keydown(input_dev, scancode, 0);
+                        toggle = (scancode & 0x2000) ? 1 : 0;
+
+                        if (scancode == data->last_code) {
+                                IR_dprintk(1, "RC-5 repeat\n");
+                                ir_repeat(input_dev);
+                        } else {
+                                data->last_code = scancode;
+                                scancode &= 0x1fff;
+                                IR_dprintk(1, "RC-5 scancode 0x%04x\n", scancode);
 
-                        data->state = STATE_TRAILER_MARK;
+                                ir_keydown(input_dev, scancode, 0);
+                        }
+                        data->state = STATE_TRAILER;
                 }
                 return 0;
-        case STATE_TRAILER_MARK:
-                if (!last_bit)
-                        goto err;
+        case STATE_TRAILER:
                 data->state = STATE_INACTIVE;
                 return 0;
         }
 
 err:
-        IR_dprintk(1, "RC-5 decoded failed at state %s (%s) @ %luus\n",
-                   st_name[data->state],
-                   bit ? "pulse" : "space",
+        IR_dprintk(1, "RC-5 decoded failed at %s @ %luus\n",
+                   is_pulse ? "pulse" : "space",
                    (ev->delta.tv_nsec + 500) / 1000);
-err2:
         data->state = STATE_INACTIVE;
         return -EINVAL;
 }