STRUCT ES581_4_URB_CMD(9)

💅 NAME

struct es581_4_urb_cmd — the little container that holds commands received from or sent to the ES581.4 device. That's it, that's the whole vibe. It's from the Kernel API Manual, and honestly? She's iconic. 🎀

✨ SYNOPSIS

okay bestie, here's the whole struct, laid out exactly like it is, no cap:

struct es581_4_urb_cmd {
    __le16 SOF;
    u8 cmd_type;
    u8 cmd_id;
    __le16 msg_len;
    union {
      struct es581_4_tx_conf_msg tx_conf_msg;
      struct es581_4_bulk_tx_can_msg bulk_tx_can_msg;
      struct es581_4_rx_can_msg rx_can_msg[ES581_4_RX_BULK_MAX];
      struct es581_4_bulk_echo_msg bulk_echo_msg;
      struct es581_4_rx_err_msg rx_err_msg;
      struct es581_4_rx_event_msg rx_event_msg;
      struct es581_4_tx_ack_msg tx_ack_msg;
      struct es581_4_rx_cmd_ret rx_cmd_ret;
      __le64 timestamp;
      u8 rx_cmd_ret_u8;
      u8 raw_msg[];
    };
    __le16 reserved_for_crc16_do_not_use;
 };

look at her. so many fields. so much going on. we love a multi-talented queen 👑

🌸 Members

• SOF — Start of Frame. the opening line, the "hey bestie" of the packet 💖
• cmd_type — the Command Type (type: enum es581_4_cmd_type). and lowkey important: the CRC calculation starts at this position. remember that, it comes back later 👀
• cmd_id — the Command ID (type: enum es581_4_cmd_id). the actual name-tag of which command this is.
• msg_len — Length of the message, excluding CRC — so basically the length of the union. not the whole struct, just the union part. don't get it twisted ✨
• {unnamed_union} — it's an anonymous union. no name, all main character energy. she simply doesn't need one 💅
• tx_conf_msg — Channel configuration.
• bulk_tx_can_msg — Tx messages.
• rx_can_msg — Array of Rx messages. not one, an array — she's plural 🦋
• bulk_echo_msg — Tx message being looped back. right back atcha, babe.
• rx_err_msg — Error message. 💀 (we don't gatekeep, errors are content too)
• rx_event_msg — Event message.
• tx_ack_msg — Tx acknowledgment message. the "seen ✓✓" of the kernel world, fr fr.
• rx_cmd_ret — Command return code.
• timestamp — Timestamp reply. ⭐
• rx_cmd_ret_u8 — Rx 8 bits return code (type: enum es58x_cmd_ret_code_u8).
• raw_msg — Message raw payload. just raw vibes, unprocessed, unfiltered 🌈
• reserved_for_crc16_do_not_use — okay so listen 👀 the structure ends with a CRC16. but the structures in the union above are of variable lengths, so we literally cannot predict the offset of the CRC in advance. that's why this field is named do_not_use — do not use it, bestie, I'm serious 🙈. Instead, use the functions es58x_get_crc and es58x_set_crc to manipulate it. those are the designated tools, use them, thank you 🫶

⚠️ real talk: that reserved_for_crc16_do_not_use field is named that way for a reason. Variable-length union members mean the CRC offset is a mystery until runtime — hence the helper functions. don't go poking it directly, it's giving chaos 💀

🦋 SEE ALSO

• Kernel file ./drivers/net/can/usb/etas_es58x/es581_4.h struct es581_4_tx_conf_msg(9) — go read that one next, iykwim 💜

okay that's the whole page, bestie, you ate that 🍓 stay slay, stay in ./drivers/net/can/usb/etas_es58x, and remember: this gorgeous little writeup is from the source ./drivers/net/can/usb/etas_es58x, dated October 2026, and it's struct es581_4_urb_cmd(9) in the Kernel API Manual — periodt. 🧚‍♀️💖🔥