pci_get_class(9)

💅 pci_get_class(9) — from the Kernel API Manual, bestie

Okay so picture this: you're deep in kernel land, you need to find a PCI device by its class, and you don't wanna write the loop yourself. That's literally this function. It's pci_get_class, and it's here to start — or keep going with — a search for a PCI device by class. 🎀

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✨ SYNOPSIS ✨

struct pci_dev * pci_get_class (unsigned int class , struct pci_dev *from );

That's the whole vibe. Two args, one pointer back out. 🫶

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🌸 ARGUMENTS 🌸

• class — the class designation you're hunting for. You want a PCI device with this class, and this is where you say so.
• from — the previous PCI device you already found in this search, or NULL if you're starting fresh. Brand new search? Pass NULL. Continuing? Pass the last one. Easy.

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🦋 DESCRIPTION 🦋

So what it actually does: it iterates through the list of known PCI devices. Iconic behavior, no notes. 💅

If a PCI device turns up with a matching class, the reference count on that device gets incremented and you get back a pointer to its device structure. Slay. You got your device.

Otherwise? NULL. That's it. That's the answer. 😭

Now, the search mechanics, because this is where people get caught out:

• You kick off a new search by passing NULL as the from argument. Fresh start, main character energy. ✨
• If from is not NULL, the search continues from the next device on the global list. Not the one you passed — the next one. iykyk.
• And listen — the reference count for from is always decremented if it is not NULL. Always. Non-negotiable. So don't go thinking you get to keep that reference, because you don't. 🫠

Heads up bestie: that automatic decrement is the whole reason this pattern works as a loop. You hand it the last thing, it lets go of it, it gives you the next thing. Trust the process. 💖

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👑 SEE ALSO 👑

Kernel file ./drivers/pci/search.c — go read it, it's giving source of truth. 🌈

And the whole friend group:

• pci_find_bus(9)
• pci_find_next_bus(9)
• pci_get_slot(9)
• pci_get_domain_bus_and_slot(9)
• pci_get_subsys(9)
• pci_get_device(9)
• pci_get_base_class(9)
• pci_dev_present(9)

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⭐ Okay that's the page!! Shoutout to ./drivers/pci for hosting, and this little love letter is dated October 2026 — go find your devices, bestie, you've got this 💜🧚🍓