[PATCH] HID: core: add usage_page_preceding flag for hid_concatenate_usage_page()

[Candle Sun]

From: Candle Sun <candle.sun@xxxxxxxxxx>

Upstream commit 58e75155009c ("HID: core: move Usage Page concatenation
to Main item") adds support for Usage Page item following Usage items
(such as keyboards manufactured by Primax).

Usage Page concatenation in Main item works well for following report
descriptor patterns:

    USAGE_PAGE (Keyboard)                   05 07
    USAGE_MINIMUM (Keyboard LeftControl)    19 E0
    USAGE_MAXIMUM (Keyboard Right GUI)      29 E7
    LOGICAL_MINIMUM (0)                     15 00
    LOGICAL_MAXIMUM (1)                     25 01
    REPORT_SIZE (1)                         75 01
    REPORT_COUNT (8)                        95 08
    INPUT (Data,Var,Abs)                    81 02

-------------

    USAGE_MINIMUM (Keyboard LeftControl)    19 E0
    USAGE_MAXIMUM (Keyboard Right GUI)      29 E7
    LOGICAL_MINIMUM (0)                     15 00
    LOGICAL_MAXIMUM (1)                     25 01
    REPORT_SIZE (1)                         75 01
    REPORT_COUNT (8)                        95 08
    USAGE_PAGE (Keyboard)                   05 07
    INPUT (Data,Var,Abs)                    81 02

But it makes the parser act wrong for the following report
descriptor pattern(such as some Gamepads):

    USAGE_PAGE (Button)                     05 09
    USAGE (Button 1)                        09 01
    USAGE (Button 2)                        09 02
    USAGE (Button 4)                        09 04
    USAGE (Button 5)                        09 05
    USAGE (Button 7)                        09 07
    USAGE (Button 8)                        09 08
    USAGE (Button 14)                       09 0E
    USAGE (Button 15)                       09 0F
    USAGE (Button 13)                       09 0D
    USAGE_PAGE (Consumer Devices)           05 0C
    USAGE (Back)                            0a 24 02
    USAGE (HomePage)                        0a 23 02
    LOGICAL_MINIMUM (0)                     15 00
    LOGICAL_MAXIMUM (1)                     25 01
    REPORT_SIZE (1)                         75 01
    REPORT_COUNT (11)                       95 0B
    INPUT (Data,Var,Abs)                    81 02

With Usage Page concatenation in Main item, parser recognizes all the
11 Usages as consumer keys, it is not the HID device's real intention.

This patch adds usage_page_preceding flag to detect the third pattern.
Usage Page concatenation is done in both Local and Main parsing.
If usage_page_preceding equals 3(the third pattern encountered),
hid_concatenate_usage_page() is jumped.

Signed-off-by: Candle Sun <candle.sun@xxxxxxxxxx>
Signed-off-by: Nianfu Bai <nianfu.bai@xxxxxxxxxx>
---
 drivers/hid/hid-core.c | 21 +++++++++++++++++++--
 include/linux/hid.h    |  1 +
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 3eaee2c..043a232 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -221,7 +221,15 @@ static int hid_add_usage(struct hid_parser *parser, unsigned usage, u8 size)
 		hid_err(parser->device, "usage index exceeded\n");
 		return -1;
 	}
-	parser->local.usage[parser->local.usage_index] = usage;
+	if (!parser->local.usage_index && parser->global.usage_page)
+		parser->local.usage_page_preceding = 1;
+	if (parser->local.usage_page_preceding == 2)
+		parser->local.usage_page_preceding = 3;
+	if (size <= 2 && parser->global.usage_page)
+		parser->local.usage[parser->local.usage_index] =
+			(usage & 0xffff) + (parser->global.usage_page << 16);
+	else
+		parser->local.usage[parser->local.usage_index] = usage;
 	parser->local.usage_size[parser->local.usage_index] = size;
 	parser->local.collection_index[parser->local.usage_index] =
 		parser->collection_stack_ptr ?
@@ -366,6 +374,8 @@ static int hid_parser_global(struct hid_parser *parser, struct hid_item *item)
 
 	case HID_GLOBAL_ITEM_TAG_USAGE_PAGE:
 		parser->global.usage_page = item_udata(item);
+		if (parser->local.usage_page_preceding == 1)
+			parser->local.usage_page_preceding = 2;
 		return 0;
 
 	case HID_GLOBAL_ITEM_TAG_LOGICAL_MINIMUM:
@@ -547,9 +557,16 @@ static void hid_concatenate_usage_page(struct hid_parser *parser)
 {
 	int i;
 
+	if (parser->local.usage_page_preceding == 3) {
+		dbg_hid("Using preceding usage page for final usage\n");
+		return;
+	}
+
 	for (i = 0; i < parser->local.usage_index; i++)
 		if (parser->local.usage_size[i] <= 2)
-			parser->local.usage[i] += parser->global.usage_page << 16;
+			parser->local.usage[i] =
+				(parser->global.usage_page << 16)
+				+ (parser->local.usage[i] & 0xffff);
 }
 
 /*
diff --git a/include/linux/hid.h b/include/linux/hid.h
index cd41f20..7fb6cf3 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -412,6 +412,7 @@ struct hid_local {
 	unsigned usage_minimum;
 	unsigned delimiter_depth;
 	unsigned delimiter_branch;
+	unsigned int usage_page_preceding;
 };
 
 /*
-- 
2.7.4