STRUCT FW_MAC(9)

🌸 struct fw_mac(9) — the Kernel API Manual, but make it make sense 🌸

okay bestie, welcome to struct fw_mac(9) — this is a page from the kernel API manual, and it's literally all about one struct. no cap, that's the whole vibe.

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✨ NAME ✨

struct fw_mac — a firmware block used by RTL_FW_PLA and RTL_FW_USB. and the layout of the firmware block is, in this exact order:

<struct fw_mac> + <info> + <firmware data>

so it's giving "header, then little info note, then the actual firmware goodies" 💅

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🎀 SYNOPSIS 🎀

here's the whole struct, character for character, don't touch:

struct fw_mac {
    struct fw_block blk_hdr;
    __le16 fw_offset;
    __le16 fw_reg;
    __le16 bp_ba_addr;
    __le16 bp_ba_value;
    __le16 bp_en_addr;
    __le16 bp_en_value;
    __le16 bp_start;
    __le16 bp_num;
    __le16 bp[16];
    __le32 reserved;
    __le16 fw_ver_reg;
    u8 fw_ver_data;
    char info[];
};

the way this is just a whole little neighborhood of fields… obsessed 🫶

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🦋 Members 🦋

• blk_hdr — the firmware descriptor. it's got the type and the length, so like, the ID card of the block 🪪
• fw_offset — the offset of the firmware binary data. the start address of that data would be the address of struct fw_mac + fw_offset. do the math, bestie ✨
• fw_reg — the register to load the firmware into. depends on chip, so no universal answer, iykyk.
• bp_ba_addr — the register you write the break point base address to. depends on chip.
• bp_ba_value — the break point base address itself. depends on chip.
• bp_en_addr — the register to write the break point enabled mask to. depends on chip.
• bp_en_value — the break point enabled mask. this one depends on the firmware, not the chip — main character energy tbh 👑
• bp_start — the start register of the break points. depends on chip.
• bp_num — the break point number that needs to be set for this firmware. depends on the firmware.
• bp — the break points. depends on firmware. yes it's an array of 16, and yes that's a lot of break points, slay 💀
• reserved — reserved space. literally unused. it's just sitting there, vibing 🙈
• fw_ver_reg — the register to store the fw version.
• fw_ver_data — the firmware version of the current type.
• info — additional information for debugging, and it's followed by the binary data of firmware. so it's the little gossip note right before the payload 🌸

quick vibe check: half these fields say "Depends on chip" and the other half say "Depends on the firmware." that's not me being vague, that's the actual documentation. don't @ me 😭

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🌈 SEE ALSO 🌈

go look at the kernel file ./drivers/net/usb/r8152.c, plus these iconic siblings:

• struct fw_block(9)
• struct fw_header(9)
• struct fw_phy_patch_key(9)
• struct fw_phy_nc(9)

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and that's the page, bestie 🎀 it lives in ./drivers/net/usb, dated October 2026, from the kernel API manual's struct fw_mac(9) edition. go read your structs, ily, bye 💖✨