scsi: ufs: Simplify response header parsing

Make the code that parses UTP transfer request headers easier to read by
using u8 instead of __be32 where appropriate.
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20230727194457.3152309-13-bvanassche@acm.orgReviewed-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

include/uapi/scsi/scsi_bsg_ufs.h

@@ -8,6 +8,7 @@
 #ifndef SCSI_BSG_UFS_H
 #define SCSI_BSG_UFS_H
 
+#include <asm/byteorder.h>
 #include <linux/types.h>
 /*
  * This file intended to be included by both kernel and user space
@@ -40,11 +41,56 @@ enum ufs_rpmb_op_type {
  * @dword_0: UPIU header DW-0
  * @dword_1: UPIU header DW-1
  * @dword_2: UPIU header DW-2
+ *
+ * @transaction_code: Type of request or response. See also enum
+ *	upiu_request_transaction and enum upiu_response_transaction.
+ * @flags: UPIU flags. The meaning of individual flags depends on the
+ *	transaction code.
+ * @lun: Logical unit number.
+ * @task_tag: Task tag.
+ * @iid: Initiator ID.
+ * @command_set_type: 0 for SCSI command set; 1 for UFS specific.
+ * @tm_function: Task management function in case of a task management request
+ *	UPIU.
+ * @query_function: Query function in case of a query request UPIU.
+ * @response: 0 for success; 1 for failure.
+ * @status: SCSI status if this is the header of a response to a SCSI command.
+ * @ehs_length: EHS length in units of 32 bytes.
+ * @device_information:
+ * @data_segment_length: data segment length.
  */
 struct utp_upiu_header {
-	__be32 dword_0;
-	__be32 dword_1;
-	__be32 dword_2;
+	union {
+		struct {
+			__be32 dword_0;
+			__be32 dword_1;
+			__be32 dword_2;
+		};
+		struct {
+			__u8 transaction_code;
+			__u8 flags;
+			__u8 lun;
+			__u8 task_tag;
+#if defined(__BIG_ENDIAN)
+			__u8 iid: 4;
+			__u8 command_set_type: 4;
+#elif defined(__LITTLE_ENDIAN)
+			__u8 command_set_type: 4;
+			__u8 iid: 4;
+#else
+#error
+#endif
+			union {
+				__u8 tm_function;
+				__u8 query_function;
+			};
+			__u8 response;
+			__u8 status;
+			__u8 ehs_length;
+			__u8 device_information;
+			__be16 data_segment_length;
+		};
+	};
 };
 
 /**

include/ufs/ufs.h

@@ -15,6 +15,12 @@
 #include <linux/types.h>
 #include <uapi/scsi/scsi_bsg_ufs.h>
 
+/*
+ * Using static_assert() is not allowed in UAPI header files. Hence the check
+ * in this header file of the size of struct utp_upiu_header.
+ */
+static_assert(sizeof(struct utp_upiu_header) == 12);
+
 #define GENERAL_UPIU_REQUEST_SIZE (sizeof(struct utp_upiu_req))
 #define QUERY_DESC_MAX_SIZE       255
 #define QUERY_DESC_MIN_SIZE       2
@@ -23,11 +29,6 @@
 					(sizeof(struct utp_upiu_header)))
 #define UFS_SENSE_SIZE	18
 
-static inline __be32 upiu_header_dword(u8 byte3, u8 byte2, u8 byte1, u8 byte0)
-{
-	return cpu_to_be32(byte3 << 24 | byte2 << 16 | byte1 << 8 | byte0);
-}
-
 /*
  * UFS device may have standard LUs and LUN id could be from 0x00 to
  * 0x7F. Standard LUs use "Peripheral Device Addressing Format".
@@ -477,14 +478,7 @@ enum {
 #define UPIU_RSP_CODE_OFFSET		8
 
 enum {
-	MASK_SCSI_STATUS		= 0xFF,
-	MASK_TASK_RESPONSE              = 0xFF00,
-	MASK_RSP_UPIU_RESULT            = 0xFFFF,
-	MASK_QUERY_DATA_SEG_LEN         = 0xFFFF,
-	MASK_RSP_UPIU_DATA_SEG_LEN	= 0xFFFF,
-	MASK_RSP_EXCEPTION_EVENT        = 0x10000,
 	MASK_TM_SERVICE_RESP		= 0xFF,
-	MASK_TM_FUNC			= 0xFF,
 };
 
 /* Task management service response */