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From:   =?UTF-8?q?Jos=C3=A9=20Exp=C3=B3sito?= <jose.exposito89@gmail.com>
To:     jikos@kernel.org
Cc:     benjamin.tissoires@redhat.com, spbnick@gmail.com,
        linux-input@vger.kernel.org, linux-kernel@vger.kernel.org,
        =?UTF-8?q?Jos=C3=A9=20Exp=C3=B3sito?= <jose.exposito89@gmail.com>
Subject: [PATCH 1/7] HID: uclogic: Support Huion tilt reporting
Date:   Thu, 10 Feb 2022 20:04:31 +0100
Message-Id: <20220210190437.50152-2-jose.exposito89@gmail.com>
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From: Nikolai Kondrashov <spbnick@gmail.com>

Add support for Huion v2 protocol tilt reporting. Describe reports as
angles in degrees, which is not exactly true, but there doesn't seem to
be a straightforward, consistent conversion possible, and what's
reported would have to be enough.

Signed-off-by: Nikolai Kondrashov <spbnick@gmail.com>
Signed-off-by: José Expósito <jose.exposito89@gmail.com>
---
 drivers/hid/hid-uclogic-core.c   |  3 +++
 drivers/hid/hid-uclogic-params.c |  1 +
 drivers/hid/hid-uclogic-params.h |  8 ++++++++
 drivers/hid/hid-uclogic-rdesc.c  | 12 +++++++++++-
 4 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-uclogic-core.c b/drivers/hid/hid-uclogic-core.c
index d8ab0139e5cd..823704bc02ef 100644
--- a/drivers/hid/hid-uclogic-core.c
+++ b/drivers/hid/hid-uclogic-core.c
@@ -304,6 +304,9 @@ static int uclogic_raw_event(struct hid_device *hdev,
 			mod_timer(&drvdata->inrange_timer,
 					jiffies + msecs_to_jiffies(100));
 		}
+		/* If we report tilt and Y direction is flipped */
+		if (size >= 12 && params->pen.tilt_y_flipped)
+			data[11] = -data[11];
 	}
 
 	/* Tweak frame control reports, if necessary */
diff --git a/drivers/hid/hid-uclogic-params.c b/drivers/hid/hid-uclogic-params.c
index 3e70f969fb84..30e0f69ed5af 100644
--- a/drivers/hid/hid-uclogic-params.c
+++ b/drivers/hid/hid-uclogic-params.c
@@ -369,6 +369,7 @@ static int uclogic_params_pen_init_v2(struct uclogic_params_pen *pen,
 	pen->id = UCLOGIC_RDESC_PEN_V2_ID;
 	pen->inrange = UCLOGIC_PARAMS_PEN_INRANGE_NONE;
 	pen->fragmented_hires = true;
+	pen->tilt_y_flipped = true;
 	found = true;
 finish:
 	*pfound = found;
diff --git a/drivers/hid/hid-uclogic-params.h b/drivers/hid/hid-uclogic-params.h
index ba48b1c7a0e5..e8381bb77bd0 100644
--- a/drivers/hid/hid-uclogic-params.h
+++ b/drivers/hid/hid-uclogic-params.h
@@ -62,6 +62,12 @@ struct uclogic_params_pen {
 	 * Only valid if "id" is not zero.
 	 */
 	bool fragmented_hires;
+	/*
+	 * True if the pen reports tilt in bytes at offset 10 (X) and 11 (Y),
+	 * and the Y tilt direction is flipped.
+	 * Only valid if "id" is not zero.
+	 */
+	bool tilt_y_flipped;
 };
 
 /*
@@ -171,6 +177,7 @@ extern int uclogic_params_init(struct uclogic_params *params,
 		".pen.id = %u\n"                    \
 		".pen.inrange = %s\n"               \
 		".pen.fragmented_hires = %s\n"      \
+		".pen.tilt_y_flipped = %s\n"        \
 		".frame.desc_ptr = %p\n"            \
 		".frame.desc_size = %u\n"           \
 		".frame.id = %u\n"                  \
@@ -189,6 +196,7 @@ extern int uclogic_params_init(struct uclogic_params *params,
 		(_params)->pen.id,                                          \
 		uclogic_params_pen_inrange_to_str((_params)->pen.inrange),  \
 		((_params)->pen.fragmented_hires ? "true" : "false"),       \
+		((_params)->pen.tilt_y_flipped ? "true" : "false"),         \
 		(_params)->frame.desc_ptr,                                  \
 		(_params)->frame.desc_size,                                 \
 		(_params)->frame.id,                                        \
diff --git a/drivers/hid/hid-uclogic-rdesc.c b/drivers/hid/hid-uclogic-rdesc.c
index 6dd6dcd09c8b..2607cbdf8ff2 100644
--- a/drivers/hid/hid-uclogic-rdesc.c
+++ b/drivers/hid/hid-uclogic-rdesc.c
@@ -633,7 +633,17 @@ const __u8 uclogic_rdesc_pen_v2_template_arr[] = {
 	0x27, UCLOGIC_RDESC_PEN_PH(PRESSURE_LM),
 				/*          Logical Maximum (PLACEHOLDER),  */
 	0x81, 0x02,             /*          Input (Variable),               */
-	0x81, 0x03,             /*          Input (Constant, Variable),     */
+	0x54,                   /*          Unit Exponent (0),              */
+	0x65, 0x14,             /*          Unit (Degrees),                 */
+	0x35, 0xC4,             /*          Physical Minimum (-60),         */
+	0x45, 0x3C,             /*          Physical Maximum (60),          */
+	0x15, 0xC4,             /*          Logical Minimum (-60),          */
+	0x25, 0x3C,             /*          Logical Maximum (60),           */
+	0x75, 0x08,             /*          Report Size (8),                */
+	0x95, 0x02,             /*          Report Count (2),               */
+	0x09, 0x3D,             /*          Usage (X Tilt),                 */
+	0x09, 0x3E,             /*          Usage (Y Tilt),                 */
+	0x81, 0x02,             /*          Input (Variable),               */
 	0xC0,                   /*      End Collection,                     */
 	0xC0                    /*  End Collection                          */
 };
-- 
2.25.1