[media] v4l2-ctrls: fix rounding calculation

Commit 958c7c7e65 ("[media] v4l2-ctrls: fix corner case in round-to-range code") broke
controls that use a negative range.

The cause was a s32/u32 mixup: ctrl->step is unsigned while all others are signed. So
the result type of the expression '(ctrl)->maximum - ((ctrl)->step / 2)' became unsigned,
making 'val >= (ctrl)->maximum - ((ctrl)->step / 2)' true, since '((u32)-128) > 128'
(if val = -128, maximum = 128 and step = 1).

So carefully cast (step / 2) to s32.

There was one cast of step to s32 where it should have been u32 because both offset and
step are unsigned, so casting to signed makes no sense there. You do need a cast to u32
there, because otherwise architectures that have no 64-bit division start complaining
(step is a u64).

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Reported-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
index 2d8ced8ad80b03831901e41d06a4b9b8c4ad215c..f030d6a9e04421f2fcd63c9fce6fc713cdc897f1 100644 (file)
--- a/drivers/media/v4l2-core/v4l2-ctrls.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls.c
@@ -1347,14 +1347,14 @@ static void std_log(const struct v4l2_ctrl *ctrl)
 ({                                                             \
        offset_type offset;                                     \
        if ((ctrl)->maximum >= 0 &&                             \
-           val >= (ctrl)->maximum - ((ctrl)->step / 2))        \
+           val >= (ctrl)->maximum - (s32)((ctrl)->step / 2))   \
                val = (ctrl)->maximum;                          \
        else                                                    \
-               val += (ctrl)->step / 2;                        \
+               val += (s32)((ctrl)->step / 2);                 \
        val = clamp_t(typeof(val), val,                         \
                      (ctrl)->minimum, (ctrl)->maximum);        \
        offset = (val) - (ctrl)->minimum;                       \
-       offset = (ctrl)->step * (offset / (s32)(ctrl)->step);   \
+       offset = (ctrl)->step * (offset / (u32)(ctrl)->step);   \
        val = (ctrl)->minimum + offset;                         \
        0;                                                      \
 })
@@ -1376,10 +1376,10 @@ static int std_validate(const struct v4l2_ctrl *ctrl, u32 idx,
                 * the u64 divide that needs special care.
                 */
                val = ptr.p_s64[idx];
-               if (ctrl->maximum >= 0 && val >= ctrl->maximum - ctrl->step / 2)
+               if (ctrl->maximum >= 0 && val >= ctrl->maximum - (s64)(ctrl->step / 2))
                        val = ctrl->maximum;
                else
-                       val += ctrl->step / 2;
+                       val += (s64)(ctrl->step / 2);
                val = clamp_t(s64, val, ctrl->minimum, ctrl->maximum);
                offset = val - ctrl->minimum;
                do_div(offset, ctrl->step);