Re: [PATCH 1/5] Input: Add input_copy_abs() function

Add a new helper function to copy absinfo from one input_dev to
another input_dev.

This is useful to e.g. setup a pen/stylus input-device for combined
touchscreen/pen hardware where the pen uses the same coordinates as
the touchscreen.

Suggested-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Hans de Goede <redacted>
---
 drivers/input/input.c | 34 ++++++++++++++++++++++++++++++++++
 include/linux/input.h |  2 ++
 2 files changed, 36 insertions(+)

diff --git a/drivers/input/input.c b/drivers/input/input.c
index ccaeb2426385..60f3eb38906f 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c

@@ -526,6 +526,40 @@ void input_set_abs_params(struct input_dev *dev, unsigned int axis,
 }
 EXPORT_SYMBOL(input_set_abs_params);
 
+/**
+ * input_copy_abs - Copy absinfo from one input_dev to another
+ * @dst: Destination input device to copy the abs settings to
+ * @dst_axis: ABS_* value selecting the destination axis
+ * @src: Source input device to copy the abs settings from
+ * @src_axis: ABS_* value selecting the source axis
+ *
+ * Set absinfo for the selected destination axis by copying it from
+ * the specified source input device's source axis.
+ * This is useful to e.g. setup a pen/stylus input-device for combined
+ * touchscreen/pen hardware where the pen uses the same coordinates as
+ * the touchscreen.
+ */
+void input_copy_abs(struct input_dev *dst, unsigned int dst_axis,
+		    const struct input_dev *src, unsigned int src_axis)
+{
+	/*
+	 * input_alloc_absinfo() may have failed for the source. Our caller is
+	 * expected to catch this when registering the input devices, which may
+	 * happen after the input_copy_abs() call.
+	 */
+	if (!src->absinfo)
+		return;

+
+	input_alloc_absinfo(dst);
+	if (!dst->absinfo)
+		return;
+
+	dst->absinfo[dst_axis] = src->absinfo[src_axis];
+
+	__set_bit(EV_ABS, dst->evbit);
+	__set_bit(dst_axis, dst->absbit);