cxl_payload...user_allowed(9)

💅 cxl_payload_from_user_allowed(9) 💅

okay bestie, so this one is a <pink>Kernel API Manual</pink> page — yes, the kernel kernel — and it's literally about giving user-space payloads a vibe check before they get anywhere near the device. no cap.

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✨ NAME ✨

cxl_payload_from_user_allowed — check contents of in_payload. that's it, that's the whole job 🎀

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🌸 SYNOPSIS 🌸

bool cxl_payload_from_user_allowed (u16 opcode , void *payload_in ,
       size_t in_size );

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🦋 ARGUMENTS 🦋

• opcode — the mailbox command opcode. it's giving "which command are we even talking about" energy 👑
• payload_in — pointer to the input payload that got passed in from user space. yes, that user space 🙈
• in_size — the size of payload_in, in bytes. count 'em, bestie 💅

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⭐ RETURN ⭐

• true — payload_in passes the check for opcode. slay, we're so back 💖
• false — payload_in contains invalid or unsupported values. not it. blocked. 💀

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🌈 DESCRIPTION 🌈

so the driver may peek at payload contents before it sends a mailbox command from user space over to the device. the whole intent here? reject commands whose input payloads are known to be unsafe. it's a bouncer at the club, basically 🫶

lowkey important: this check is not meant to replace the user carefully selecting mailbox command parameters. it also makes no guarantee that the user command will succeed, and no guarantee that it's even appropriate. it's a vibe check, not a promise, iykyk 😭

the specific checks? those are determined by the opcode. different command, different rules. periodt. ✨

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🧚 SEE ALSO 🧚

kernel file ./drivers/cxl/core/mbox.c cxl mbox(9), plus the whole friend group:

• cxl_internal_send_cmd(9)
• cxl_validate_cmd_from_user(9)
• handle_mailbox_cmd_from_user(9)
• cxl_walk_cel(9)
• cxl_enumerate_cmds(9)
• cxl_mem_get_event_records(9)
• cxl_mem_get_partition_info(9)
• cxl_dev_state_identify(9)
• cxl_mem_sanitize(9)

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and that's the whole page, bestie 🍓 shoutout to <cyan>./drivers/cxl/core</cyan> for dropping this one, dated <yellow>October 2026` — same energy, same manual, mwah 💜🦋