mma9551_read_config_byte(9)

📦 version 7.3.1, in nixpkgs unstable

💅 mma9551_read_config_byte — like, the whole vibe ✨

Okay bestie, so this one's a kernel API manual page — it lives in section 9 of the manual, and the star of the show is mma9551_read_config_byte. Yes, that's a mouthful, but it's giving "small function, big responsibilities" and honestly? We love her for it. 🎀

✨ NAME ✨

mma9551_read_config_byte — read exactly one configuration byte. That's it. That's the whole job. One byte. No cap. 🦋

🌸 SYNOPSIS 🌸

int mma9551_read_config_byte (struct i2c_client *client , u8 app_id ,
       u16 reg , u8 *val );

Look at her. Clean. Iconic. Returns an int, takes four things. Periodt. 💅

🧚 ARGUMENTS 🧚

  • client — the I2C client. Your device's whole identity, basically her main character energy. 👑
  • app_id — the Application ID. Which app we're talking to inside the chip, iykyk.
  • reg — the application register. The exact spot we're poking at. 📍
  • val — pointer to store the value read. That's where the byte lands so you can actually look at it. 🍓

💖 DESCRIPTION 💖

So here's the tea: this function reads one configuration byte from the device, and it does it using the MMA955xL command format. 🫶

And what does that command format look like? Commands to the MMA955xL platform consist of a write followed by one or more reads. That's the whole dance — write first, then read. Every time. Don't skip steps. 🔥

⚠️ Locking note, and this is important so listen up: this function must be called with the device lock held. Locking is not handled inside the function. That's your job, caller. Callers should ensure they serialize access to the HW. Not me, not the function — you. Please don't make it weird. 😭💀

⭐ RETURN ⭐

  • 0 on success 🎉
  • a negative value on failure 😭

That's the whole contract. Zero means slay, negative means something went sideways.

🌈 SEE ALSO 🌈

Y'all, the friend group is huge and we're linking all of them, no one gets left out. 💜

Kernel file ./drivers/iio/accel/mma9551_core.c — that's where the source lives, go read it, it's giving required reading.

And that's the page, bestie! 🦋 Before you go — the whole thing comes from ./drivers/iio/accel, dated October 2026. Screenshot it, memorize it, put it on your wall, whatever. Mwah! 💅✨🎀

📦 where this page comes from