m88ts2022: fix 32bit overflow on filter calc

Maximum satellite symbol rate used is 45000000Sps which overflows when multiplied by 135. As final calculation result is fraction, we could use mult_frac macro in order to keep calculation inside 32 bit number limits and prevent overflow.

Original bug and fix was provided by Nibble Max. I decided to implement it differently as it is now.

Reported-by Nibble Max <[email protected]>

Cc <[email protected]>

Signed-off-by Antti Palosaari <[email protected]>

---
drivers/media/tuners/m88ts2022.c | 2 +-

1 file changed, 1 insertion(+), 1 deletion(-)

drivers/media/tuners/m88ts2022.c +1 -1

index 40c42de..7a62097 100644
@@ -314,7 +314,7 @@ static int m88ts2022_set_params(struct dvb_frontend *fe)
 	div_min = gdiv28 * 78 / 100;
 	div_max = clamp_val(div_max, 0U, 63U);
 
-	f_3db_hz = c->symbol_rate * 135UL / 200UL;
+	f_3db_hz = mult_frac(c->symbol_rate, 135, 200);
 	f_3db_hz +=  2000000U + (frequency_offset_khz * 1000U);
 	f_3db_hz = clamp(f_3db_hz, 7000000U, 40000000U);
 

Signature · 1 line

http://palosaari.fi/