STRUCT HBM_CAPABILITY_RESPONSE(9)

💅 struct hbm_capability_response(9) — the Kernel API Manual, bestie edition ✨

okay so this is struct hbm_capability_response(9) from the kernel API manual, and honestly? she's small but she's important. 🎀

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🌸 NAME 🌸

struct hbm_capability_response — the capability response that fw sends back to host, no cap 💌

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✨ SYNOPSIS ✨

struct hbm_capability_response {
    u8 hbm_cmd;
    u8 capability_granted[3];
 };

like, that's the whole struct. three-ish lines. short queen energy 👑 (the original really does have that slightly-off indent on the closing brace, and I'm keeping it exactly as-is, don't @ me 🫶)

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🦋 Members 🦋

• hbm_cmd — the bus message command header 📨 literally just the command header for the bus message.
• capability_granted — bitmask of capabilities granted by FW ✅🔓 it's a bitmask, so each bit is a different capability the firmware said yes to. fw really said "you may" and handed over a whole bitfield, we love a generous icon.

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💜 SEE ALSO 💜

Kernel file ./drivers/misc/mei/hw.h — go read it, it's giving source of truth 📖✨

and then the whole lil family of related entries, all of them, in order, because we do not skip anyone in this house:

• enum mei_hbm_status(9)
• enum mei_ext_hdr_type(9)
• struct mei_ext_hdr(9)
• struct mei_ext_meta_hdr(9)
• struct mei_ext_hdr_vtag(9)
• mei_ext_begin(9)
• mei_ext_last(9)
• struct mei_ext_hdr_gsc_h2f(9)
• struct mei_ext_hdr_gsc_f2h(9)
• mei_ext_next(9)
• mei_ext_hdr_len(9)
• struct mei_msg_hdr(9)
• struct mei_hbm_cl_cmd(9)
• enum hbm_host_enum_flags(9)
• struct hbm_host_enum_request(9)
• struct mei_client_properties(9)
• struct hbm_add_client_request(9)
• struct hbm_add_client_response(9)
• struct hbm_power_gate(9)
• struct hbm_client_connect_request(9)
• struct hbm_client_connect_response(9)
• struct hbm_notification_request(9)
• struct hbm_notification_response(9)
• struct hbm_notification(9)
• struct hbm_dma_mem_dscr(9)
• struct hbm_dma_setup_request(9)
• struct hbm_dma_setup_response(9)
• struct hbm_dma_ring_ctrl(9)
• struct hbm_capability_request(9) ← her sister, the request 🥺 the pair of them, iconic
• struct hbm_client_dma_map_request(9)
• struct hbm_client_dma_unmap_request(9)
• struct hbm_client_dma_response(9)

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lowkey a whole extended universe going on in ./drivers/misc/mei/hw.h and this struct is just one little star in the constellation ⭐ don't forget the request-side twin struct hbm_capability_request(9), they come as a set iykyk

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🧚 sign-off 🧚

that's the whole page, bestie! it lives under ./drivers/misc/mei, this edition is dated October 2026, and the title up top is struct hbm_capability_response(9) in case you forgot already 💖 bye ily, go read your headers 🦋🌸