[PATCH] HID: simplify code in fetch_item()

Dmitry Torokhov
2024-10-01T15:42:39Z

We can easily calculate the size of the item using arithmetic (shifts).
This allows to pull duplicated code out of the switch statement, making
it cleaner.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
drivers/hid/hid-core.c | 31 ++++++++++++++-----------------
1 file changed, 14 insertions(+), 17 deletions(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 988d0acbdf04..00942d40fe08 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -754,35 +754,32 @@ static u8 *fetch_item(__u8 *start, __u8 *end, struct hid_item *item)
}

item->format = HID_ITEM_FORMAT_SHORT;
- item->size = b & 3;
+ item->size = BIT(b & 3) >> 1; /* 0, 1, 2, 3 -> 0, 1, 2, 4 */
+
+ if (end - start < item->size)
+ return NULL;

switch (item->size) {
case 0:
- return start;
+ break;

case 1:
- if ((end - start) < 1)
- return NULL;
- item->data.u8 = *start++;
- return start;
+ item->data.u8 = *start;
+ break;

case 2:
- if ((end - start) < 2)
- return NULL;
item->data.u16 = get_unaligned_le16(start);
- start = (__u8 *)((__le16 *)start + 1);
- return start;
+ break;

- case 3:
- item->size++;
- if ((end - start) < 4)
- return NULL;
+ case 4:
item->data.u32 = get_unaligned_le32(start);
- start = (__u8 *)((__le32 *)start + 1);
- return start;
+ break;
+
+ default:
+ unreachable();
}

- return NULL;
+ return start + item->size;
}

static void hid_scan_input_usage(struct hid_parser *parser, u32 usage)
--
2.46.1.824.gd892dcdcdd-goog

--
Dmitry