STRUCT UTP_UPIU_HEADER(9)

okay bestie, you're on the struct utp_upiu_header(9) page from the Kernel API Manual 💖 this is the UPIU header structure, and we're gonna keep every single member, flag, and literal exactly as it is. No skips, no cap 🫶

✨ NAME ✨

struct utp_upiu_header — UPIU header structure. Short, sweet, iconic ✨

🌸 SYNOPSIS 🌸

Here's the struct, copied exactly — braces, semicolons, endianness branches, all of it 💅

       struct utp_upiu_header {
           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;
             };
           };
        };

🧚 Members 🧚

Okay, member-by-member, in source order. The source repeats command_set_type and iid, so they appear twice below too — not a typo, that's just the tea 💀

• {unnamed_union} — anonymous
• {unnamed_struct} — anonymous
• dword_0 — UPIU header DW-0
• dword_1 — UPIU header DW-1
• dword_2 — UPIU header DW-2
• {unnamed_struct} — anonymous
• 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.
• command_set_type — 0 for SCSI command set; 1 for UFS specific.
• iid — Initiator ID.
• {unnamed_union} — anonymous
• 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 — (no description in the source, so no invented tea 🙈)
• data_segment_length — data segment length.

🌈 SEE ALSO 🌈

• Kernel file ./include/uapi/scsi/scsi_bsg_ufs.h plus struct utp_upiu_query(9), struct utp_upiu_query_v4_0(9), struct utp_upiu_cmd(9), struct utp_upiu_req(9) — that's the whole reference crew 🫶

Source/version line points at ./include/uapi/scsi, date says October 2026, and the page is struct utp_upiu_header(9) — bye bestie, go be iconic with your structs 🎀💖