From: Vincent Mailhol mailhol.vincent@wanadoo.fr
[ Upstream commit 1a6dd9996699889313327be03981716a8337656b ]
clang emits a -Wunaligned-access warning on union mcp251xfd_tx_ojb_load_buf.
The reason is that field hw_tx_obj (not declared as packed) is being packed right after a 16 bits field inside a packed struct:
| union mcp251xfd_tx_obj_load_buf { | struct __packed { | struct mcp251xfd_buf_cmd cmd; | /* ^ 16 bits fields */ | struct mcp251xfd_hw_tx_obj_raw hw_tx_obj; | /* ^ not declared as packed */ | } nocrc; | struct __packed { | struct mcp251xfd_buf_cmd_crc cmd; | struct mcp251xfd_hw_tx_obj_raw hw_tx_obj; | __be16 crc; | } crc; | } ____cacheline_aligned;
Starting from LLVM 14, having an unpacked struct nested in a packed struct triggers a warning. c.f. [1].
This is a false positive because the field is always being accessed with the relevant put_unaligned_*() function. Adding __packed to the structure declaration silences the warning.
[1] https://github.com/llvm/llvm-project/issues/55520
Link: https://lore.kernel.org/all/20220518114357.55452-1-mailhol.vincent@wanadoo.f... Signed-off-by: Vincent Mailhol mailhol.vincent@wanadoo.fr Reported-by: kernel test robot lkp@intel.com Tested-by: Nathan Chancellor nathan@kernel.org # build Signed-off-by: Marc Kleine-Budde mkl@pengutronix.de Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/can/spi/mcp251xfd/mcp251xfd.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd.h b/drivers/net/can/spi/mcp251xfd/mcp251xfd.h index 0f322dabaf65..281856eea2ef 100644 --- a/drivers/net/can/spi/mcp251xfd/mcp251xfd.h +++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd.h @@ -433,7 +433,7 @@ struct mcp251xfd_hw_tef_obj { /* The tx_obj_raw version is used in spi async, i.e. without * regmap. We have to take care of endianness ourselves. */ -struct mcp251xfd_hw_tx_obj_raw { +struct __packed mcp251xfd_hw_tx_obj_raw { __le32 id; __le32 flags; u8 data[sizeof_field(struct canfd_frame, data)];