diff options
Diffstat (limited to 'Documentation/input/multi-touch-protocol.txt')
| -rw-r--r-- | Documentation/input/multi-touch-protocol.txt | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/Documentation/input/multi-touch-protocol.txt b/Documentation/input/multi-touch-protocol.txt index 2c179613f81..7b4f59c09ee 100644 --- a/Documentation/input/multi-touch-protocol.txt +++ b/Documentation/input/multi-touch-protocol.txt @@ -80,6 +80,8 @@ Userspace can detect that a driver can report more total contacts than slots by noting that the largest supported BTN_TOOL_*TAP event is larger than the total number of type B slots reported in the absinfo for the ABS_MT_SLOT axis. +The minimum value of the ABS_MT_SLOT axis must be 0. + Protocol Example A ------------------ @@ -370,7 +372,7 @@ simple scheme, which is compatible with earlier usage, is: Rationale: We have no information about the orientation of the touching ellipse, so approximate it with an inscribed circle instead. The tool -ellipse should align with the the vector (T - C), so the diameter must +ellipse should align with the vector (T - C), so the diameter must increase with distance(T, C). Finally, assume that the touch diameter is equal to the tool thickness, and we arrive at the formulas above. |