amdgpu_debu...ocess_reg_op(9)

📦 version 7.3.1, in nixpkgs unstable

💅 amdgpu_debugfs_process_reg_op 💅

okay so bestie, this is a page from the Kernel API Manual, section 9 of the manual pages — the one and only amdgpu_debugfs_process_reg_op(9) 🎀. yes the header truncates the name with that ... thing, that's just the man page being extra about column width, the actual function is the full thing. buckle up, we're reading MMIO registers together 🦋

✨ NAME ✨

amdgpu_debugfs_process_reg_op — literally the handler for MMIO register reads and writes 💅

🌸 SYNOPSIS 🌸

int  amdgpu_debugfs_process_reg_op (bool read , struct file *f , char
       __user *buf , size_t size , loff_t *pos );

like, that's the whole signature, no cap ✨

🫶 ARGUMENTS 🫶

  • read — True if you're reading. that's it, that's the vibe check. true = read, and if it's not true you're writing, iykyk 💖
  • f — the open file handle 🎀
  • buf — the user buffer you're writing to, or reading from 🦋
  • size — how many bytes we're writing/reading, bestie, be precise 🌸
  • pos — the offset you're seeking to ⭐

👑 DESCRIPTION 👑

okay so here's the iconic part: this debugfs entry gives the offset you seek special meaning. like, the offset isn't just an offset anymore, it's carrying extra info in its bits. various bits do different things 🔥

🧚 the bit assignments (learn them, love them)

  • Bit 62: says a GRBM bank switch is needed
  • Bit 61: says a SRBM bank switch is needed (and yes, this implies bit 62 is zero)
  • Bits 24..33: the SE or ME selector, if it's needed
  • Bits 34..43: the SH (or SA) or PIPE selector, if it's needed
  • Bits 44..53: the INSTANCE (or CU/WGP) or QUEUE selector, if it's needed

💜 and one more very important bit

  • Bit 23: says the PM power gating lock should be held 🫶 — and this one is necessary to read registers that might be unreliable during a power gating transition. so like, don't skip it, it's giving "load-bearing bit", fr fr 😭

🍓 the low bits, aka the actual address

the lower bits are the BYTE offset of the register to read 💖 and the way this slaps is that it lets you read multiple registers in a single call and have the returned size reflect that. one syscall, many registers, main character energy 👑

🌈 SEE ALSO 🌈

the kernel file lives right here, go be nosy:

./drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c

and the whole friend group 💅:

and that's the page, bestie 🫶 sourced straight from ./drivers/gpu/drm/amd/amdgpu, dated October 2026 — mwah, go read some registers responsibly 💋✨🎀

📦 where this page comes from