netdev - [PATCH net 15/15] can: mcp251xfd: mcp251xfd_register_get_dev

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Date:   Mon,  4 Jul 2022 14:26:13 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, kuba@...nel.org, linux-can@...r.kernel.org,
        kernel@...gutronix.de, Marc Kleine-Budde <mkl@...gutronix.de>,
        Rasmus Villemoes <rasmus.villemoes@...vas.dk>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Subject: [PATCH net 15/15] can: mcp251xfd: mcp251xfd_register_get_dev_id(): fix endianness conversion

In mcp251xfd_register_get_dev_id() the device ID register is read with
handcrafted SPI transfers. As all registers, this register is in
little endian. Further it is not naturally aligned in struct
mcp251xfd_map_buf_nocrc::data. However after the transfer the register
content is converted from big endian to CPU endianness not taking care
of being unaligned.

Fix the conversion by converting from little endian to CPU endianness
taking the unaligned source into account.

Side note: So far the register content is 0x0 on all mcp251xfd
compatible chips, and is only used for an informative printk.

Link: https://lore.kernel.org/all/20220627092859.809042-1-mkl@pengutronix.de
Fixes: 55e5b97f003e ("can: mcp25xxfd: add driver for Microchip MCP25xxFD SPI CAN")
Reviewed-by: Rasmus Villemoes <rasmus.villemoes@...vas.dk>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Signed-off-by: Marc Kleine-Budde <mkl@...gutronix.de>
---
 drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
index 3160881e89d9..9b47b07162fe 100644
--- a/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
+++ b/drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c
@@ -12,6 +12,7 @@
 // Copyright (c) 2019 Martin Sperl <kernel@...tin.sperl.org>
 //
 
+#include <asm/unaligned.h>
 #include <linux/bitfield.h>
 #include <linux/clk.h>
 #include <linux/device.h>
@@ -1787,7 +1788,7 @@ mcp251xfd_register_get_dev_id(const struct mcp251xfd_priv *priv, u32 *dev_id,
 	if (err)
 		goto out_kfree_buf_tx;
 
-	*dev_id = be32_to_cpup((__be32 *)buf_rx->data);
+	*dev_id = get_unaligned_le32(buf_rx->data);
 	*effective_speed_hz_slow = xfer[0].effective_speed_hz;
 	*effective_speed_hz_fast = xfer[1].effective_speed_hz;
 
-- 
2.35.1