[PATCH] HID: core: use flex array allocation

[Rosen Penev <rosenp@gmail.com>]

Instead of embedding a pointer in the struct, use a flexible array
member to avoid the + 1 trick to point to allocation after the struct.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 drivers/hid/hid-core.c | 6 ++----
 include/linux/hid.h    | 2 +-
 2 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 840a60113868..6bd6cbf26c6d 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -127,15 +127,13 @@ static struct hid_field *hid_register_field(struct hid_report *report, unsigned
 		return NULL;
 	}
 
-	field = kvzalloc((sizeof(struct hid_field) +
-			  usages * sizeof(struct hid_usage) +
-			  3 * usages * sizeof(unsigned int)), GFP_KERNEL);
+	field = kvzalloc(struct_size(field, usage, usages) +
+			  3 * usages * sizeof(unsigned int), GFP_KERNEL);
 	if (!field)
 		return NULL;
 
 	field->index = report->maxfield++;
 	report->field[field->index] = field;
-	field->usage = (struct hid_usage *)(field + 1);
 	field->value = (s32 *)(field->usage + usages);
 	field->new_value = (s32 *)(field->value + usages);
 	field->usages_priorities = (s32 *)(field->new_value + usages);
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 2990b9f94cb5..e2c3e2528582 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -524,7 +524,6 @@ struct hid_field {
 	unsigned  physical;		/* physical usage for this field */
 	unsigned  logical;		/* logical usage for this field */
 	unsigned  application;		/* application usage for this field */
-	struct hid_usage *usage;	/* usage table for this function */
 	unsigned  maxusage;		/* maximum usage index */
 	unsigned  flags;		/* main-item flags (i.e. volatile,array,constant) */
 	unsigned  report_offset;	/* bit offset in the report */
@@ -549,6 +548,7 @@ struct hid_field {
 	struct hid_input *hidinput;	/* associated input structure */
 	__u16 dpad;			/* dpad input code */
 	unsigned int slot_idx;		/* slot index in a report */
+	struct hid_usage usage[];	/* usage table for this function */
 };
 
 #define HID_MAX_FIELDS 256
-- 
2.53.0