[media] fixp-arith: replace sin/cos table by a better precision one

The cos table used at fixp-arith.h has only 8 bits of precision.
That causes problems if it is reused on other drivers.

As some media drivers require a higher precision sin/cos
implementation, replace the current implementation by one that
will provide 32 bits precision.

The values generated by the new implementation matches the
32 bit precision of glibc's sin for an angle measured in
integer degrees.

It also provides support for fractional angles via linear
interpolation. On experimental calculus, when used a table
with a 0.001 degree angle, the maximum error for sin is
0.000038, which is likely good enough for practical purposes.

There are some logic there that seems to be specific to the
usage inside ff-memless.c. Move those logic to there, as they're
not needed elsewhere.

Cc: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Signed-off-by: Prashant Laddha <prladdha@cisco.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

2 files changed, 18 insertions, 11 deletions

diff --git a/drivers/input/ff-memless.c b/drivers/input/ff-memless.c
index 74c0d8c6002a..fcc6c3368182 100644
--- a/drivers/input/ff-memless.c
+++ b/drivers/input/ff-memless.c
@@ -237,6 +237,18 @@ static u16 ml_calculate_direction(u16 direction, u16 force,
 		(force + new_force)) << 1;
 }
 
+#define FRAC_N 8
+static inline s16 fixp_new16(s16 a)
+{
+	return ((s32)a) >> (16 - FRAC_N);
+}
+
+static inline s16 fixp_mult(s16 a, s16 b)
+{
+	a = ((s32)a * 0x100) / 0x7fff;
+	return ((s32)(a * b)) >> FRAC_N;
+}
+
 /*
  * Combine two effects and apply gain.
  */
@@ -247,7 +259,7 @@ static void ml_combine_effects(struct ff_effect *effect,
 	struct ff_effect *new = state->effect;
 	unsigned int strong, weak, i;
 	int x, y;
-	fixp_t level;
+	s16 level;
 
 	switch (new->type) {
 	case FF_CONSTANT:
@@ -255,8 +267,8 @@ static void ml_combine_effects(struct ff_effect *effect,
 		level = fixp_new16(apply_envelope(state,
 					new->u.constant.level,
 					&new->u.constant.envelope));
-		x = fixp_mult(fixp_sin(i), level) * gain / 0xffff;
-		y = fixp_mult(-fixp_cos(i), level) * gain / 0xffff;
+		x = fixp_mult(fixp_sin16(i), level) * gain / 0xffff;
+		y = fixp_mult(-fixp_cos16(i), level) * gain / 0xffff;
 		/*
 		 * here we abuse ff_ramp to hold x and y of constant force
 		 * If in future any driver wants something else than x and y
diff --git a/drivers/media/usb/gspca/ov534.c b/drivers/media/usb/gspca/ov534.c
index a9c866d6d82d..146071b8e116 100644
--- a/drivers/media/usb/gspca/ov534.c
+++ b/drivers/media/usb/gspca/ov534.c
@@ -816,21 +816,16 @@ static void sethue(struct gspca_dev *gspca_dev, s32 val)
 		s16 huesin;
 		s16 huecos;
 
-		/* fixp_sin and fixp_cos accept only positive values, while
-		 * our val is between -90 and 90
-		 */
-		val += 360;
-
 		/* According to the datasheet the registers expect HUESIN and
 		 * HUECOS to be the result of the trigonometric functions,
 		 * scaled by 0x80.
 		 *
-		 * The 0x100 here represents the maximun absolute value
+		 * The 0x7fff here represents the maximum absolute value
 		 * returned byt fixp_sin and fixp_cos, so the scaling will
 		 * consider the result like in the interval [-1.0, 1.0].
 		 */
-		huesin = fixp_sin(val) * 0x80 / 0x100;
-		huecos = fixp_cos(val) * 0x80 / 0x100;
+		huesin = fixp_sin16(val) * 0x80 / 0x7fff;
+		huecos = fixp_cos16(val) * 0x80 / 0x7fff;
 
 		if (huesin < 0) {
 			sccb_reg_write(gspca_dev, 0xab,