mptctl_syscall_down(9)

💖 mptctl_syscall_down(9) 💖

okay so bestie, welcome to the Kernel API Manual ✨ this is section 9, the kernel dev corner of the manual, and today's main character is mptctl_syscall_down — say it with me, it's giving "down the semaphore" energy and we're obsessed 💅

🌸 NAME 🌸

mptctl_syscall_down — down the MPT adapter syscall semaphore 😌🔒

🦋 SYNOPSIS 🦋

int mptctl_syscall_down (MPT_ADAPTER *ioc , int nonblock );

ngl that's the whole footprint, and yes the spacing is exactly like that, don't come for me 🙈

🎀 ARGUMENTS 🎀

• ioc — pointer to the MPT adapter, like, the actual adapter we're doing syscall things to 🫶
• nonblock — a boolean, and it's non-zero if O_NONBLOCK is set ✨ (zero means it isn't, iykyk)

🌈 DESCRIPTION 🌈

okay so here's the tea ☕ — all of the ioctl commands can potentially sleep, and sleeping while you're holding a spinlock is illegal, full stop, no cap 😭💀 so we do the mutual exclusion right here instead. That's the whole job. It's not glamorous, but it's iconic. 👑

Returns a negative errno on error, or zero for success — that's it, that's the vibe check ⭐

🧚 SEE ALSO 🧚

Kernel file ./drivers/message/fusion/mptctl.c — go read it, it's lowkey the source of truth 💜

and that's the page, bestie 🎀 huge thanks to the fine folks in ./drivers/message/fusion for this one — this little writeup is dated October 2026 and it lives in mptctl_syscall_down(9), slay, periodt 💅✨🦋