Before this commit lis3lv02d_get_pwron_wait() had a WARN_ONCE() to catch a potential divide by 0. WARN macros should only be used to catch internal kernel bugs and that is not the case here. We have been receiving a lot of bug reports about kernel backtraces caused by this WARN.

The div value being checked comes from the lis3->odrs[] array. Which is sized to be a power-of-2 matching the number of bits in lis3->odr_mask.

The only lis3 model where this array is not entirely filled with non zero values. IOW the only model where we can hit the div == 0 check is the 3dc ("8 bits 3DC sensor") model:

int lis3_3dc_rates[16] = {0, 1, 10, 25, 50, 100, 200, 400, 1600, 5000};

Note the 0 value at index 0, according to the datasheet an odr index of 0 means "Power-down mode". HP typically uses a lis3 accelerometer for HDD fall protection. What I believe is happening here is that on newer HP devices, which only contain a SDD, the BIOS is leaving the lis3 device powered-down since it is not used for HDD fall protection.

Note that the lis3_3dc_rates array initializer only specifies 10 values, which matches the datasheet. So it also contains 6 zero values at the end.

Replace the WARN with a normal check, which treats an odr index of 0 as power-down and uses a normal dev_err() to report the error in case odr index point past the initialized part of the array.

BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=785814 BugLink: https://bugzilla.redhat.com/show_bug.cgi?id=1817027 BugLink: https://bugs.centos.org/view.php?id=10720 Fixes: 1510dd5954be ("lis3lv02d: avoid divide by zero due to unchecked") Cc: stable@vger.kernel.org Signed-off-by: Hans de Goede hdegoede@redhat.com --- drivers/misc/lis3lv02d/lis3lv02d.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/misc/lis3lv02d/lis3lv02d.c b/drivers/misc/lis3lv02d/lis3lv02d.c index dd65cedf3b12..9d14bf444481 100644 --- a/drivers/misc/lis3lv02d/lis3lv02d.c +++ b/drivers/misc/lis3lv02d/lis3lv02d.c @@ -208,7 +208,7 @@ static int lis3_3dc_rates[16] = {0, 1, 10, 25, 50, 100, 200, 400, 1600, 5000}; static int lis3_3dlh_rates[4] = {50, 100, 400, 1000};

/* ODR is Output Data Rate */ -static int lis3lv02d_get_odr(struct lis3lv02d *lis3) +static int lis3lv02d_get_odr_index(struct lis3lv02d *lis3) { u8 ctrl; int shift; @@ -216,15 +216,23 @@ static int lis3lv02d_get_odr(struct lis3lv02d *lis3) lis3->read(lis3, CTRL_REG1, &ctrl); ctrl &= lis3->odr_mask; shift = ffs(lis3->odr_mask) - 1; - return lis3->odrs[(ctrl >> shift)]; + return (ctrl >> shift); }

static int lis3lv02d_get_pwron_wait(struct lis3lv02d *lis3) { - int div = lis3lv02d_get_odr(lis3); + int odr_idx = lis3lv02d_get_odr_index(lis3); + int div = lis3->odrs[odr_idx];

- if (WARN_ONCE(div == 0, "device returned spurious data")) + if (div == 0) { + if (odr_idx == 0) { + /* Power-down mode, not sampling no need to sleep */ + return 0; + } + + dev_err(&lis3->pdev->dev, "Error unknown odrs-index: %d\n", odr_idx); return -ENXIO; + }

/* LIS3 power on delay is quite long */ msleep(lis3->pwron_delay / div); @@ -816,9 +824,12 @@ static ssize_t lis3lv02d_rate_show(struct device *dev, struct device_attribute *attr, char *buf) { struct lis3lv02d *lis3 = dev_get_drvdata(dev); + int odr_idx;

lis3lv02d_sysfs_poweron(lis3); - return sprintf(buf, "%d\n", lis3lv02d_get_odr(lis3)); + + odr_idx = lis3lv02d_get_odr_index(lis3); + return sprintf(buf, "%d\n", lis3->odrs[odr_idx]); }

static ssize_t lis3lv02d_rate_set(struct device *dev,