cxl_validate_cmd_from_user(9)

📦 version 7.3.1, in nixpkgs unstable

💅 cxl_validate_cmd_from_user(9) — like, the vibe check for CXL_MEM_SEND_COMMAND

okay so bestie, welcome to the Kernel API Manual, and today's main character is cxl_validate_cmd_from_user(9). she's the one who looks at whatever userspace just handed the kernel and goes "mm, no, this is safe" or "absolutely not, blocked." no cap, she's the bouncer at the CXL club 🎀

✨ NAME ✨

cxl_validate_cmd_from_user — the function that does the field check for CXL_MEM_SEND_COMMAND. like, every single field. she's thorough 💅

🦋 SYNOPSIS 🦋

int cxl_validate_cmd_from_user (struct cxl_mbox_cmd *mbox_cmd , struct
cxl_mailbox *cxl_mbox , const struct cxl_send_command *send_cmd );

literally the whole signature, copied exactly, because we do not mess with code around here 🫶

🌸 ARGUMENTS 🌸

  • mbox_cmd — the struct cxl_mbox_cmd that comes out the other side all sanitized and populated. she goes in a mess and comes out iconic ✨
  • cxl_mbox — the CXL mailbox context. the setting, the scene, the environment our girl is working in 🎀
  • send_cmd — the struct cxl_send_command that got copied in from userspace. yes, straight from userspace, so you know we gotta check it 🙈

💀 RETURN 💀

here's the tea on what she gives back, bestie:

  • 0 — out_cmd is ready to send. slay. green light, go off 👑
  • -ENOTTY — invalid command specified. that command? not a real one. not today 💀
  • -EINVAL — reserved fields or invalid values were used. someone did not read the spec, and she noticed 😭
  • -ENOMEM — the input or output buffer wasn't sized properly. wrong size, wrong energy. no 🍓
  • -EPERM — attempted to use a protected command. that one's protected, babe, hands off 🔥
  • -EBUSY — the kernel has claimed exclusive access to this opcode. it's taken. it's busy. move along 💅

🧚 DESCRIPTION 🧚

so like, the result of this function is a fully validated command sitting in mbox_cmd that is safe to send to the hardware. that's the whole glow-up: unsanitized input walks in, validated-and-safe commands walk out, and the hardware never has to see the messy version. obsessed 🌈

fr fr though — this is the trust boundary between userspace and your hardware. she's not being extra, she's being correct 💜

⭐ SEE ALSO ⭐

go read these next, iykwiyk:

okay that's the whole page, bestie, go forth and validate responsibly 🫶

sign-off time: this little number lives under ./drivers/cxl/core, dated October 2026, and it's the cxl_validate_cmd_from_user(9) page from the Kernel API Manual. mwah 💋✨

📦 where this page comes from