Hi Dan,
On 09/04/2018 05:40 AM, Dan Carpenter wrote:
Hello Guenter Roeck,
The patch bbd8decd4123: "hwmon: (nct6775) Add support for weighted
fan control" from Dec 4, 2012, leads to the following static checker
warning:
drivers/hwmon/nct6775.c:1562 nct6775_update_pwm()
warn: dead code because of 'j == 1' and 'j < (56 / 8 + 0)'
drivers/hwmon/nct6775.c
1503 static void nct6775_update_pwm(struct device *dev)
1504 {
1505 struct nct6775_data *data = dev_get_drvdata(dev);
1506 int i, j;
1507 int fanmodecfg, reg;
1508 bool duty_is_dc;
1509
1510 for (i = 0; i < data->pwm_num; i++) {
1511 if (!(data->has_pwm & BIT(i)))
1512 continue;
1513
1514 duty_is_dc = data->REG_PWM_MODE[i] &&
1515 (nct6775_read_value(data, data->REG_PWM_MODE[i])
1516 & data->PWM_MODE_MASK[i]);
1517 data->pwm_mode[i] = !duty_is_dc;
1518
1519 fanmodecfg = nct6775_read_value(data, data->REG_FAN_MODE[i]);
1520 for (j = 0; j < ARRAY_SIZE(data->REG_PWM); j++) {
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
j is set to ARRAY_SIZE(data->REG_PWM) which is 7 at the end of this
loop.
1521 if (data->REG_PWM[j] && data->REG_PWM[j][i]) {
1522 data->pwm[j][i]
1523 = nct6775_read_value(data,
1524 data->REG_PWM[j][i]);
1525 }
1526 }
1527
1528 data->pwm_enable[i] = reg_to_pwm_enable(data->pwm[0][i],
1529 (fanmodecfg >> 4) & 7);
1530
1531 if (!data->temp_tolerance[0][i] ||
1532 data->pwm_enable[i] != speed_cruise)
1533 data->temp_tolerance[0][i] = fanmodecfg & 0x0f;
1534 if (!data->target_speed_tolerance[i] ||
1535 data->pwm_enable[i] == speed_cruise) {
1536 u8 t = fanmodecfg & 0x0f;
1537
1538 if (data->REG_TOLERANCE_H) {
1539 t |= (nct6775_read_value(data,
1540 data->REG_TOLERANCE_H[i]) & 0x70) >> 1;
1541 }
1542 data->target_speed_tolerance[i] = t;
1543 }
1544
1545 data->temp_tolerance[1][i] =
1546 nct6775_read_value(data,
1547 data->REG_CRITICAL_TEMP_TOLERANCE[i]);
1548
1549 reg = nct6775_read_value(data, data->REG_TEMP_SEL[i]);
1550 data->pwm_temp_sel[i] = reg & 0x1f;
1551 /* If fan can stop, report floor as 0 */
1552 if (reg & 0x80)
1553 data->pwm[2][i] = 0;
1554
1555 if (!data->REG_WEIGHT_TEMP_SEL[i])
1556 continue;
1557
1558 reg = nct6775_read_value(data, data->REG_WEIGHT_TEMP_SEL[i]);
1559 data->pwm_weight_temp_sel[i] = reg & 0x1f;
1560 /* If weight is disabled, report weight source as 0 */
1561 if (j == 1 && !(reg & 0x80))
^^^^^^
So it can't be 1 here. Did you intend to say "i == 1"?
Nice catch. No, the condition does not depend on an index and should simply be
if (!(reg & 0x80))
No idea what if anything I was thinking when I wrote the code.
It would be great if you can send a patch.
Thanks,
Guenter
1562 data->pwm_weight_temp_sel[i] = 0;
1563
1564 /* Weight temp data */
1565 for (j = 0; j < ARRAY_SIZE(data->weight_temp); j++) {
1566 data->weight_temp[j][i]
1567 = nct6775_read_value(data,
1568 data->REG_WEIGHT_TEMP[j][i]);
1569 }
1570 }
1571 }
regards,
dan carpenter
