ASoC: SDCA: Add bounds check for function address

SDCA only supports 3-bits for the function address, but the ACPI value
is 64-bits. Update the code that parses this to do a bounds check
and error out on invalid addresses. Currently, an invalid address
would truncate to the bottom 3-bits when used and thus use a likely
incorrect address. With the bounds check, it is also now safe to
shrink the size of the adr member of sdca_function_desc to a u8 and
rearrange the struct members to pack better with the new size of adr.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://patch.msgid.link/20241220173516.907406-3-ckeepax@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: charleskeepax

include/sound/sdca.h

@@ -23,9 +23,9 @@ struct sdw_slave;
  * @name: human-readable string
  */
 struct sdca_function_desc {
-	u64 adr;
-	u32 type;
 	const char *name;
+	u32 type;
+	u8 adr;
 };
 
 /**

sound/soc/sdca/sdca_functions.c

@@ -108,17 +108,12 @@ static int find_sdca_function(struct acpi_device *adev, void *data)
 		return -EINVAL;
 	}
 
-	/*
-	 * The number of functions cannot exceed 8, we could use
-	 * acpi_get_local_address() but the value is stored as u64 so
-	 * we might as well avoid casts and intermediate levels
-	 */
 	ret = acpi_get_local_u64_address(adev->handle, &addr);
 	if (ret < 0)
 		return ret;
 
-	if (!addr) {
-		dev_err(dev, "no addr\n");
+	if (!addr || addr > 0x7) {
+		dev_err(dev, "invalid addr: 0x%llx\n", addr);
 		return -ENODEV;
 	}