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From:   Benjamin Tissoires <benjamin.tissoires@redhat.com>
To:     Jiri Kosina <jikos@kernel.org>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Jonathan Corbet <corbet@lwn.net>,
        =?UTF-8?q?Ahelenia=20Ziemia=C5=84ska?= 
        <nabijaczleweli@nabijaczleweli.xyz>,
        Ping Cheng <pinglinux@gmail.com>,
        Aaron Armstrong Skomra <skomra@gmail.com>,
        Jason Gerecke <killertofu@gmail.com>,
        Peter Hutterer <peter.hutterer@who-t.net>
Cc:     linux-input@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Benjamin Tissoires <benjamin.tissoires@redhat.com>
Subject: [PATCH 11/12] HID: input: accommodate priorities for slotted devices
Date:   Wed, 26 Jan 2022 17:18:31 +0100
Message-Id: <20220126161832.3193805-12-benjamin.tissoires@redhat.com>
In-Reply-To: <20220126161832.3193805-1-benjamin.tissoires@redhat.com>
References: <20220126161832.3193805-1-benjamin.tissoires@redhat.com>
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Multitouch devices in hybrid mode are reporting multiple times the
same collection. We should accommodate for this in our handling
of priorities by defining the slots they belong to.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
---
 drivers/hid/hid-input.c | 103 ++++++++++++++++++++++++++++++++++++----
 include/linux/hid.h     |   1 +
 2 files changed, 96 insertions(+), 8 deletions(-)

diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index 2d13d3ad9d3c..1b00fa363668 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -48,6 +48,16 @@ static const struct {
 	__s32 y;
 }  hid_hat_to_axis[] = {{ 0, 0}, { 0,-1}, { 1,-1}, { 1, 0}, { 1, 1}, { 0, 1}, {-1, 1}, {-1, 0}, {-1,-1}};
 
+struct usage_priority {
+	__u32 usage;			/* the HID usage associated */
+	bool global;			/* we assume all usages to be slotted,
+					 * unless global
+					 */
+	unsigned int slot_overwrite;	/* for globals: allows to set the usage
+					 * before or after the slots
+					 */
+};
+
 /*
  * hid-input will convert this list into priorities:
  * the first element will have the highest priority
@@ -57,17 +67,30 @@ static const struct {
  * hid-input will then shift the priority by 8 bits to leave some space
  * in case drivers want to interleave other fields.
  *
+ * To accommodate slotted devices, the slot priority is
+ * defined in the next 8 bits (defined by 0xff - slot).
+ *
  * If drivers want to add fields before those, hid-input will
  * leave out the first 8 bits of the priority value.
  *
  * This still leaves us 65535 individual priority values.
  */
-static const __u32 hidinput_usages_priorities[] = {
-	HID_DG_ERASER,		/* Eraser (eraser touching) must always come before tipswitch */
-	HID_DG_INVERT,		/* Invert must always come before In Range */
-	HID_DG_TIPSWITCH,	/* Is the tip of the tool touching? */
-	HID_DG_TIPPRESSURE,	/* Tip Pressure might emulate tip switch */
-	HID_DG_INRANGE,		/* In Range needs to come after the other tool states */
+static const struct usage_priority hidinput_usages_priorities[] = {
+	{ /* Eraser (eraser touching) must always come before tipswitch */
+	  .usage = HID_DG_ERASER,
+	},
+	{ /* Invert must always come before In Range */
+	  .usage = HID_DG_INVERT,
+	},
+	{ /* Is the tip of the tool touching? */
+	  .usage = HID_DG_TIPSWITCH,
+	},
+	{ /* Tip Pressure might emulate tip switch */
+	  .usage = HID_DG_TIPPRESSURE,
+	},
+	{ /* In Range needs to come after the other tool states */
+	  .usage = HID_DG_INRANGE,
+	},
 };
 
 #define map_abs(c)	hid_map_usage(hidinput, usage, &bit, &max, EV_ABS, (c))
@@ -612,6 +635,7 @@ static void hidinput_configure_usage(struct hid_input *hidinput, struct hid_fiel
 {
 	struct input_dev *input = hidinput->input;
 	struct hid_device *device = input_get_drvdata(input);
+	const struct usage_priority *usage_priority = NULL;
 	int max = 0, code;
 	unsigned int i = 0;
 	unsigned long *bit = NULL;
@@ -633,13 +657,26 @@ static void hidinput_configure_usage(struct hid_input *hidinput, struct hid_fiel
 
 	/* assign a priority based on the static list declared here */
 	for (i = 0; i < ARRAY_SIZE(hidinput_usages_priorities); i++) {
-		if (usage->hid == hidinput_usages_priorities[i]) {
+		if (usage->hid == hidinput_usages_priorities[i].usage) {
+			usage_priority = &hidinput_usages_priorities[i];
+
 			field->usages_priorities[usage_index] =
 				(ARRAY_SIZE(hidinput_usages_priorities) - i) << 8;
 			break;
 		}
 	}
 
+	/*
+	 * For slotted devices, we need to also add the slot index
+	 * in the priority.
+	 */
+	if (usage_priority && usage_priority->global)
+		field->usages_priorities[usage_index] |=
+			usage_priority->slot_overwrite;
+	else
+		field->usages_priorities[usage_index] |=
+			(0xff - field->slot_idx) << 16;
+
 	if (device->driver->input_mapping) {
 		int ret = device->driver->input_mapping(device, hidinput, field,
 				usage, &bit, &max);
@@ -2034,7 +2071,57 @@ static struct hid_input *hidinput_match_application(struct hid_report *report)
 static inline void hidinput_configure_usages(struct hid_input *hidinput,
 					     struct hid_report *report)
 {
-	int i, j;
+	int i, j, k;
+	int first_field_index = 0;
+	int slot_collection_index = -1;
+	int prev_collection_index = -1;
+	unsigned int slot_idx = 0;
+	struct hid_field *field;
+
+	/*
+	 * First tag all the fields that are part of a slot,
+	 * a slot needs to have one Contact ID in the collection
+	 */
+	for (i = 0; i < report->maxfield; i++) {
+		field = report->field[i];
+
+		/* ignore fields without usage */
+		if (field->maxusage < 1)
+			continue;
+
+		/*
+		 * janitoring when collection_index changes
+		 */
+		if (prev_collection_index != field->usage->collection_index) {
+			prev_collection_index = field->usage->collection_index;
+			first_field_index = i;
+		}
+
+		/*
+		 * if we already found a Contact ID in the collection,
+		 * tag and continue to the next.
+		 */
+		if (slot_collection_index == field->usage->collection_index) {
+			field->slot_idx = slot_idx;
+			continue;
+		}
+
+		/* check if the current field has Contact ID */
+		for (j = 0; j < field->maxusage; j++) {
+			if (field->usage[j].hid == HID_DG_CONTACTID) {
+				slot_collection_index = field->usage->collection_index;
+				slot_idx++;
+
+				/*
+				 * mark all previous fields and this one in the
+				 * current collection to be slotted.
+				 */
+				for (k = first_field_index; k <= i; k++)
+					report->field[k]->slot_idx = slot_idx;
+				break;
+			}
+		}
+	}
 
 	for (i = 0; i < report->maxfield; i++)
 		for (j = 0; j < report->field[i]->maxusage; j++)
diff --git a/include/linux/hid.h b/include/linux/hid.h
index feb8df61168f..4363a63b9775 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -492,6 +492,7 @@ struct hid_field {
 	/* hidinput data */
 	struct hid_input *hidinput;	/* associated input structure */
 	__u16 dpad;			/* dpad input code */
+	unsigned int slot_idx;		/* slot index in a report */
 };
 
 #define HID_MAX_FIELDS 256
-- 
2.33.1