mma9551_read_status_byte(9)

📦 version 7.3.1, in nixpkgs unstable

💅 mma9551_read_status_byte — read 1 status byte ✨

okay bestie, so this one lives in the Kernel API Manual, and honestly? it's giving "tiny function, big responsibility." Let's get into it 🫶

🌸 SYNOPSIS 🌸

int mma9551_read_status_byte (struct i2c_client *client , u8 app_id ,
       u16 reg , u8 *val );

literally just one status byte. one. that's the whole gig. slay 💅

🎀 ARGUMENTS 🎀

  • client — the I2C client, aka your device's lil handle to the bus. bestie needs it to talk to the hardware 🦋
  • app_id — the Application ID. yes, apps have IDs here too, we're in the kernel, everything's got an ID ✨
  • reg — the Application register you're pointing at. this is the where 🌸
  • val — a pointer to store value read. this is where the byte lands once we've grabbed it. the receipt, if you will 🧾💖

👑 DESCRIPTION 👑

So what it does: it reads one status byte from the device, using the MMA955xL command format. iconic 💫

And the way the MMA955xL platform does commands? ngl it's a lil two-step: commands to the MMA955xL platform consist of a write followed by one or more reads. write first, then read, then maybe read some more. that's the vibe check ✅

⚠️ Locking note, and this is the important part bestie, do NOT skip it: This function must be called with the device lock held. Locking is not handled inside the function. Callers should ensure they serialize access to the HW. fr fr. no cap. if you call this without the lock you're on your own and I will be praying for you 🙈💀

⭐ RETURN ⭐

  • 0 on success 🎉
  • negative value on failure 😭

that's it. that's the whole return contract. 0 or sad. 🎀

🔥 SEE ALSO 🔥

the kernel file in question, literally right here:

Kernel file ./drivers/iio/accel/mma9551_core.c

and the whole squad, the mma9551 family reunion, all in one place 👑✨:

like, the whole friend group showed up for the function. we love to see it 🫶💖

and that's the page, bestie! this lil slice of kernel lore comes from ./drivers/iio/accel, dated October 2026, in the Kernel API Manual. go forth, hold that device lock, and read exactly one (1) status byte 💜🎀✨

📦 where this page comes from