serdev_device_write(9)

📦 version 7.3.1, in nixpkgs unstable

💅 serdev_device_write — the Kernel API Manual page you actually wanna read

Okay bestie, so this is serdev_device_write(9) from the Kernel API Manual, and honestly? It's giving "write it and forget it" — except you can't forget it, because it's synchronous. Let me walk you through it. 🎀

✨ NAME ✨

serdev_device_write — write data synchronously ✍️💫

🦋 SYNOPSIS 🦋

ssize_t serdev_device_write (struct serdev_device *serdev , const u8
*buf , size_t count , long timeout );

That's the whole vibe. Four args, one ssize_t back. Slay.

🌸 ARGUMENTS 🌸

  • serdev — the serdev device itself, your main character 🫶
  • buf — the data you wanna write, the actual bytes, no cap
  • count — how many bytes to write, like literally the number
  • timeout — timeout in jiffies, or 0 to wait indefinitely (yes, forever-forever, don't say I didn't warn you 😭)

💖 DESCRIPTION 💖

So here's the tea: you write data to the device synchronously, and it does this by repeatedly calling serdev_device_write until the controller has accepted all the data — unless it gets interrupted by a timeout or a signal. Rude, but okay. 💀

ngl there are two notes here and they're both important, so pay attention bestie:
  • Any accepted data has only been buffered by the controller. So if you actually want the controller write buffer to be genuinely emptied, use serdev_device_wait_until_sent. Like, actually actually. ⭐
  • This function depends on serdev_device_write_wakeup being called in the serdev driver write_wakeup callback. That's the whole engine, iykyk. 🔥

🔥 RETURN 🔥

Here's the vibe check on what comes back:

  • The number of bytes written — this can be less than count if it got interrupted 👀
  • -ETIMEDOUT or -ERESTARTSYS if it got interrupted before any bytes were written
  • Or a negative errno on errors, the classic 😔

🌈 SEE ALSO 🌈

Peep the kernel file ./drivers/tty/serdev/core.c, plus the whole friend group:

✨ that's the whole page, bestie ✨

This iconic lil doc comes from ./drivers/tty/serdev, dated October 2026, and it's literally titled serdev_device_write(9). Go write some bytes, you absolute legend 💅👑💜

📦 where this page comes from