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can: ems_usb: fix clang's -Wunaligned-access warning

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commit a4cb6e62ea4d36e53fb3c0f18ea4503d7b76674f upstream.

clang emits a -Wunaligned-access warning on struct __packed
ems_cpc_msg.

The reason is that the anonymous union msg (not declared as packed) is
being packed right after some non naturally aligned variables (3*8
bits + 2*32) inside a packed struct:

| struct __packed ems_cpc_msg {
| 	u8 type;	/* type of message */
| 	u8 length;	/* length of data within union 'msg' */
| 	u8 msgid;	/* confirmation handle */
| 	__le32 ts_sec;	/* timestamp in seconds */
| 	__le32 ts_nsec;	/* timestamp in nano seconds */
|	/* ^ not naturally aligned */
|
| 	union {
| 	/* ^ not declared as packed */
| 		u8 generic[64];
| 		struct cpc_can_msg can_msg;
| 		struct cpc_can_params can_params;
| 		struct cpc_confirm confirmation;
| 		struct cpc_overrun overrun;
| 		struct cpc_can_error error;
| 		struct cpc_can_err_counter err_counter;
| 		u8 can_state;
| 	} msg;
| };

Starting from LLVM 14, having an unpacked struct nested in a packed
struct triggers a warning. c.f. [1].

Fix the warning by marking the anonymous union as packed.

[1] https://github.com/llvm/llvm-project/issues/55520

Fixes: 702171adee ("ems_usb: Added support for EMS CPC-USB/ARM7 CAN/USB interface")
Link: https://lore.kernel.org/all/20220802094021.959858-1-mkl@pengutronix.de
Cc: Gerhard Uttenthaler <uttenthaler@ems-wuensche.com>
Cc: Sebastian Haas <haas@ems-wuensche.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Marc Kleine-Budde 2022-08-01 22:47:16 +02:00 committed by Greg Kroah-Hartman
parent f67c43e4b1
commit 45be56968d
1 changed files with 1 additions and 1 deletions
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2
drivers/net/can/usb/ems_usb.c
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@ -194,7 +194,7 @@ struct __packed ems_cpc_msg {
__le32 ts_sec; /* timestamp in seconds */ __le32 ts_sec; /* timestamp in seconds */
__le32 ts_nsec; /* timestamp in nano seconds */ __le32 ts_nsec; /* timestamp in nano seconds */
union { union __packed {
u8 generic[64]; u8 generic[64];
struct cpc_can_msg can_msg; struct cpc_can_msg can_msg;
struct cpc_can_params can_params; struct cpc_can_params can_params;