dev_err_probe(9)

📦 version 7.3.1, in nixpkgs unstable

💅 dev_err_probe — probe error check and log helper ✨

okay bestie, so this page is dev_err_probe(9) from the Kernel API Manual — yes, that kernel, the big one 🐧 — and it's honestly such a glow-up of a helper. let me tell you all about it 🫶

✨ SYNOPSIS ✨

int dev_err_probe (const struct device *dev , int err , const char *fmt
, ... );

like, that's the whole vibe. one function, three-ish args, infinite slay 💅

🎀 ARGUMENTS 🎀

  • dev — the pointer to the struct device. your device. the main character 👑
  • err — the error value to test. yes we're testing it, hold that thought 🧚
  • fmt — printf-style format string. you know the drill 💖
  • ... — arguments as specified in the format string. the lil entourage 🌸

💖 DESCRIPTION 💖

so this helper implements the common pattern that's literally everywhere in probe functions for error checking. it prints a debug or error message depending on whether the error value is -EPROBE_DEFER, and then propagates the error upwards. iconique behavior, no notes 💅

and bestie, in case of -EPROBE_DEFER it also sets the defer probe reason, which you can check later by reading the devices_deferred debugfs attribute. so it's not just logging, it's leaving receipts 📝✨

it replaces this whole code sequence:

if (err != -EPROBE_DEFER)
        dev_err(dev, ...);
else
        dev_dbg(dev, ...);
return err;

with just:

return dev_err_probe(dev, err, ...);

the way that's so much shorter?? like, the compiler girlies ate with this one 🔥

🦋 a couple little things you should know 🦋

using this helper in your probe function is totally fine even if err is known to never be -EPROBE_DEFER. no gatekeeping here, it's valid 🌈

the benefit compared to a normal dev_err is the standardized format of the error code, which gets emitted symbolically — i.e. you get "EAGAIN" instead of "-35". way more readable, way more cutesy 🎀 and having the error code returned allows more compact error paths. tidy queen behavior ✨

Returns err. that's it. that's the return. it returns err 💜

🌸 SEE ALSO 🌸

kernel file ./drivers/base/core.c, plus the whole extended friend group of device/devlink/fwnode lore — not me listing every single one, but bestie i promised no skips so here we go 💀

and that's the page!! mwah 💋 this one lives in ./drivers/base and it's dated October 2026, and the page itself is literally just dev_err_probe(9) — so yeah, go forth and return your errors cute and symbolic ✨🎀💜

📦 where this page comes from