inv_icm42600...te_watermark(9)

💅 NAME 💅

inv_icm42600_buffer_update_watermark — update watermark FIFO threshold

ok so bestie, this is from the Kernel API Manual and it's literally the glow-up function for your FIFO watermark threshold ✨

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🦋 SYNOPSIS 🦋

int inv_icm42600_buffer_update_watermark (struct inv_icm42600_state *st
);

one function, one arg, let's go 💖

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🎀 ARGUMENTS 🎀

• st — driver internal state. that's it, that's the whole mood. it's the driver's own lil state blob 🫶

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👑 DESCRIPTION 👑

So the tea is: this returns 0 on success, or a negative error code if things went sideways 😭 that's the whole contract, no cap.

Now for the actual main character energy: the FIFO watermark threshold gets computed based on the required watermark values you set for the gyro and the accel sensors 🔥

And here's the vibe check — watermark is literally all about acceptable data latency, so you go with the smallest setting between the two. Sounds easy right? 🙈 It means you're choosing the smallest latency… but ngl it is not as simple as picking the smallest watermark value, because latency depends on watermark AND ODR. It's giving multi-step drama. It requires several steps:

1. compute gyro and accel latencies and choose the smallest value.
2. adapt the chosen latency so that it is a multiple of both gyro and accel ones. Otherwise it is possible that you don't meet a requirement. (for example with gyro 100Hz wm 4 and accel 100Hz with wm 6, choosing the value of 4 will not meet accel latency requirement because 6 is not a multiple of 4. You need to use the value 2.) 💀
3. Since all periods are multiple of each others, watermark is computed by dividing this computed latency by the smallest period, which corresponds to the FIFO frequency.

⚠️ Beware that this is only true because we are not using 500Hz frequency which is not a multiple of the others. girl. do NOT forget this one, it's load-bearing 🌸

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🌈 SEE ALSO 🌈

• Kernel file ./drivers/iio/imu/inv_icm42600/inv_icm42600_buffer.c — go read the source bestie, it ate 💅

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ok that's the whole page, you're welcome 🧚💜

signing off from ./drivers/iio/imu/inv_icm42600, dated October 2026 — stay hydrated, stay watermarked, and remember: the smallest watermark is not always the smallest latency, iykyk ⭐🍓