vmw_execbuf_copy_fence_user(9)

📦 version 7.3.1, in nixpkgs unstable

💖 vmw_execbuf_copy_fence_user(9) — Kernel API Manual ✨

okay so bestie, this one lives in the Kernel API Manual and it's basically the little messenger that hands fence info back to userspace. tiny function, big "please don't let this copy fail" energy. let's get into it 🫶

✨ NAME ✨

vmw_execbuf_copy_fence_user — copy fence object information to userspace. like, literally that's the whole job 💅

🌸 SYNOPSIS 🌸

int vmw_execbuf_copy_fence_user (struct vmw_private *dev_priv , struct
       vmw_fpriv *vmw_fp , int ret , struct drm_vmw_fence_rep __user
       *user_fence_rep , struct vmw_fence_obj *fence , uint32_t fence_handle ,
       int32_t out_fence_fd );

seven params, no cap. she's thorough 🔥

🎀 ARGUMENTS 🎀

  • dev_priv — pointer to a vmw_private struct. the main character of the vmwgfx universe tbh 👑
  • vmw_fp — pointer to the struct vmw_fpriv that represents the calling file. so we know who is asking 😌
  • ret — the return value from fence object creation. yeah, we're passing a return value in. it's giving "receipts" 🧾
  • user_fence_rep — the userspace address of a struct drm_vmw_fence_rep, and that's where the info gets copied to. destination unlocked 📬
  • fence — pointer to the fenc object. yes, the page really spells it fenc, not me, I would never 🙈 (it means the fence object)
  • fence_handle — the userspace fence handle. that's the little id userspace holds onto 🎫
  • out_fence_fd — the exported file descriptor for the fence. and it's -1 if it's not used, so don't come for her when it's negative 🍓

🦋 DESCRIPTION 🦋

so, the whole point: this function copies fence information to userspace. that's it, that's the vibe check ✅

now the messy part, and I need you to stay with me: if copying fails, the userspace struct drm_vmw_fence_rep::error member is hopefully left untouched — and if userspace preloaded it with an -EFAULT, the error will hopefully be detected. yes, "hopefully" twice. she said it, not me, the manpage is being honest about the coping mechanism 😭

also, if copying fails, userspace is gonna be unable to signal the fence object, so we wait for it immediately and then unreference the userspace reference. lowkey the graceful-exit arc of this function 💀

heads up: those are the documented behaviours, "hopefully" included, fr fr. I'm not adding lore.

👑 SEE ALSO 👑

the kernel file is ./drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c — that's the neighborhood bestie 🏡

and then, and I'm not kidding, the whole friend group:

that's the whole group chat, everyone showed up, nobody left on read 🌈

and that's the page!! mwah 💋 this little number comes from ./drivers/gpu/drm/vmwgfx, dated October 2026, and she answers to vmw_execbuf_copy_fence_user(9) — go say hi, she's iconic, periodt 💜🎀

📦 where this page comes from