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authorSiarhei Vishniakou2022-07-08 21:59:23 -0700
committerDmitry Torokhov2022-07-08 22:02:00 -0700
commit2a96271fb66c499e4a89d76a89d3d01170c10bef (patch)
tree6c9b0c307da7c342dc5e6fb754d59057aa684a22 /include
parent3de93e6ed2df6521e3f68fb45eec0bb4fe1bb218 (diff)
Input: document the units for resolution of size axes
Today, the resolution of size axes is not documented. As a result, it's not clear what the canonical interpretation of this value should be. On Android, there is a need to calculate the size of the touch ellipse in physical units (millimeters). After reviewing linux source, it turned out that most of the existing usages are already interpreting this value as "units/mm". This documentation will make it explicit. This will help device implementations with correctly following the linux specs, and will ensure that the devices will work on Android without needing further customized parameters for scaling of major/minor values. Signed-off-by: Siarhei Vishniakou <svv@google.com> Reviewed-by: Jeff LaBundy <jeff@labundy.com> Link: https://lore.kernel.org/r/20220520084514.3451193-1-svv@google.com Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Diffstat (limited to 'include')
-rw-r--r--include/uapi/linux/input.h11
1 files changed, 7 insertions, 4 deletions
diff --git a/include/uapi/linux/input.h b/include/uapi/linux/input.h
index ee3127461ee0..328cf545c029 100644
--- a/include/uapi/linux/input.h
+++ b/include/uapi/linux/input.h
@@ -78,10 +78,13 @@ struct input_id {
* Note that input core does not clamp reported values to the
* [minimum, maximum] limits, such task is left to userspace.
*
- * The default resolution for main axes (ABS_X, ABS_Y, ABS_Z)
- * is reported in units per millimeter (units/mm), resolution
- * for rotational axes (ABS_RX, ABS_RY, ABS_RZ) is reported
- * in units per radian.
+ * The default resolution for main axes (ABS_X, ABS_Y, ABS_Z,
+ * ABS_MT_POSITION_X, ABS_MT_POSITION_Y) is reported in units
+ * per millimeter (units/mm), resolution for rotational axes
+ * (ABS_RX, ABS_RY, ABS_RZ) is reported in units per radian.
+ * The resolution for the size axes (ABS_MT_TOUCH_MAJOR,
+ * ABS_MT_TOUCH_MINOR, ABS_MT_WIDTH_MAJOR, ABS_MT_WIDTH_MINOR)
+ * is reported in units per millimeter (units/mm).
* When INPUT_PROP_ACCELEROMETER is set the resolution changes.
* The main axes (ABS_X, ABS_Y, ABS_Z) are then reported in
* units per g (units/g) and in units per degree per second