V4L/DVB (6501): stv0297: Signal strength fixes

Fixes the signal strength value (higher value = higher signal strength)
and scales the value to the range of 0..ffff. The characteristic itself
is wrong. To get proper values on a TT-C2300 in the range of 40..60%
real signal strength, the values from the patch should be divide by two.
The attached patch doesn't fix the characteristic.

Signed-off-by: Hartmut Birr <e9hack@googlemail.com>
Signed-off-by: Oliver Endriss <o.endriss@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

1 files changed, 17 insertions, 5 deletions

diff --git a/drivers/media/dvb/frontends/stv0297.c b/drivers/media/dvb/frontends/stv0297.c
index 17e5cb561cd8..7c23775f77db 100644
--- a/drivers/media/dvb/frontends/stv0297.c
+++ b/drivers/media/dvb/frontends/stv0297.c
@@ -358,11 +358,23 @@ static int stv0297_read_ber(struct dvb_frontend *fe, u32 * ber)
 static int stv0297_read_signal_strength(struct dvb_frontend *fe, u16 * strength)
 {
         struct stv0297_state *state = fe->demodulator_priv;
-        u8 STRENGTH[2];
-
-        stv0297_readregs(state, 0x41, STRENGTH, 2);
-        *strength = (STRENGTH[1] & 0x03) << 8 | STRENGTH[0];
-
+        u8 STRENGTH[3];
+        u16 tmp;
+
+        stv0297_readregs(state, 0x41, STRENGTH, 3);
+        tmp = (STRENGTH[1] & 0x03) << 8 | STRENGTH[0];
+        if (STRENGTH[2] & 0x20) {
+                if (tmp < 0x200)
+                        tmp = 0;
+                else
+                        tmp = tmp - 0x200;
+        } else {
+                if (tmp > 0x1ff)
+                        tmp = 0;
+                else
+                        tmp = 0x1ff - tmp;
+        }
+        *strength = (tmp << 7) | (tmp >> 2);
         return 0;
 }