media: mb86a16: avoid division by zero
As warned by smatch:
drivers/media/dvb-frontends/mb86a16.c:1690 mb86a16_read_ber() error: uninitialized symbol 'timer'.
drivers/media/dvb-frontends/mb86a16.c:1706 mb86a16_read_ber() error: uninitialized symbol 'timer'.
There is a potential risk of doing a division by zero if
timer is not handled well. Enforce it by setting a bit mask
for the values used to select the timer.
It should be noticed that I don't have mb86a16 datasheet. So,
the bitmask was guessed based on the existing checks for
the field. At worse case scenario, it will just show a
badly calculated bit error rate, but it won't crash.
While here, optimize the logic to prevent uneeded tests.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
diff --git a/drivers/media/dvb-frontends/mb86a16.c b/drivers/media/dvb-frontends/mb86a16.c
index f1aad52..5d2bb76 100644
--- a/drivers/media/dvb-frontends/mb86a16.c
+++ b/drivers/media/dvb-frontends/mb86a16.c
@@ -1677,15 +1677,15 @@
* the deinterleaver output.
* monitored BER is expressed as a 20 bit output in total
*/
- ber_rst = ber_mon >> 3;
+ ber_rst = (ber_mon >> 3) & 0x03;
*ber = (((ber_msb << 8) | ber_mid) << 8) | ber_lsb;
if (ber_rst == 0)
timer = 12500000;
- if (ber_rst == 1)
+ else if (ber_rst == 1)
timer = 25000000;
- if (ber_rst == 2)
+ else if (ber_rst == 2)
timer = 50000000;
- if (ber_rst == 3)
+ else /* ber_rst == 3 */
timer = 100000000;
*ber /= timer;
@@ -1697,11 +1697,11 @@
* QPSK demodulator output.
* monitored BER is expressed as a 24 bit output in total
*/
- ber_tim = ber_mon >> 1;
+ ber_tim = (ber_mon >> 1) & 0x01;
*ber = (((ber_msb << 8) | ber_mid) << 8) | ber_lsb;
if (ber_tim == 0)
timer = 16;
- if (ber_tim == 1)
+ else /* ber_tim == 1 */
timer = 24;
*ber /= 2 ^ timer;