SLPC H2G MESSAGE FORMAT(9)

🎀 SLPC H2G MESSAGE FORMAT 🎀

okay bestie, so this is a page from the Kernel API Manual, section 9, and it's literally just the ✨ layout ✨ of the SLPC host-to-GUC (H2G) message. Like, the actual byte-by-byte fit check for the vibe. Every bit is accounted for, no cap. Here's the whole thing, exactly as it's drawn:

       ┌────────────────────────────┐
       │         Bits   Description │
       └────────────────────────────┘
       +===+=======+==============================================================+
       | 0 |    31 | ORIGIN = GUC_HXG_ORIGIN_HOST_
       | |
       +-------+--------------------------------------------------------------+
       |   | 30:28 | TYPE = GUC_HXG_TYPE_REQUEST_
       | |
       +-------+--------------------------------------------------------------+
       |   | 27:16 | DATA0 = MBZ
       | |
       +-------+--------------------------------------------------------------+
       |   |  15:0 | ACTION = _`GUC_ACTION_HOST2GUC_PC_SLPM_REQUEST` = 0x3003
       |

       ┌─────────────────────────────┐
       │     1   31:8   **EVENT_ID** │
       └─────────────────────────────┘
       +
       +-------+--------------------------------------------------------------+
       |   |   7:0 | **EVENT_ARGC** - number of data arguments
       |

       ┌──────────────────────────────────┐
       │     2     31:0   **EVENT_DATA1** │
       │     ...   31:0   ...             │
       │     2+n   31:0   **EVENT_DATAn** │
       └──────────────────────────────────┘

so let's break down the drama, slot by slot 💅

• slot 0 — the header era, it's giving very structured:
  • bits 31 — ORIGIN = GUC_HXG_ORIGIN_HOST_. hi, it's the host calling 🫶
  • bits 30:28 — TYPE = GUC_HXG_TYPE_REQUEST_. it's a request, obviously, main character energy
  • bits 27:16 — DATA0 = MBZ. that's Must Be Zero, so please, keep it zero, no notes ✨
  • bits 15:0 — ACTION = GUC_ACTION_HOST2GUC_PC_SLPM_REQUEST, and it equals 0x3003. iconic hex moment 🔥
• slot 1 — the event details:
  • bits 31:8 — EVENT_ID
  • bits 7:0 — EVENT_ARGC — the number of data arguments, i.e. how many payload besties are coming next
• slot 2 … slot 2+n — the payload parade 🌈:
  • slot 2, bits 31:0 — EVENT_DATA1
  • ... bits 31:0 — ...
  • slot 2+n, bits 31:0 — EVENT_DATAn

like, the way n is just matching up with EVENT_ARGC? the math is mathing, we love a consistent queen 👑

👀 SEE ALSO 👀

go read these next, fr fr:

• the kernel file ./drivers/gpu/drm/xe/abi/guc_actions_slpc_abi.h
• SLPC SHARED DATA STRUCTURE(9)
• SETUP_PC_GUCRC(9)

and that's the whole page, bestie 🦋 it lives in ./drivers/gpu/drm/xe/abi, it's from October 2026, and it's part of the Kernel API Manual (section 9, SLPC H2G MESSAGE FORMAT). tysm for reading, stan a bitfield for clear skin 💖✨