PCI_FIND_NEXT_EXT_CAP(9)

💅 PCI_FIND_NEXT_EXT_CAP(9) — like, the extended capability hunter

okay so bestie, welcome to the Kernel API Manual ✨ this one's a function-style macro situation and honestly? she's iconic. her whole job is finding a PCI extended capability for you. no cap. 🎀

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🌸 NAME 🌸

PCI_FIND_NEXT_EXT_CAP — the girl who goes and finds a PCI extended capability for you 💖

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✨ SYNOPSIS ✨

PCI_FIND_NEXT_EXT_CAP (read_cfg , start , cap , prev_ptr , args... );

like, that's the whole call. yes it's a macro, yes it takes varargs, yes we're living. 🦋

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🎀 ARGUMENTS 🎀

• read_cfg — a function pointer for reading PCI config space. that's your little reader helper, she does the actual reading 🫶
• start — where to begin the search. pass 0 for the very first search, like starting a fresh scroll 💅
• cap — the extended capability ID you're hunting for. the one. the main character 👑
• prev_ptr — pointer where we stash the position of the preceding capability. it's optional, no pressure 😌
• args — extra arguments you pass along to read_cfg. hand 'em over 🍓

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🔥 DESCRIPTION 🔥

so what she does is: search the extended capability list in PCI config space to find cap 💖

if she finds it, she updates *prev_ptr with the position of the preceding capability — but only if prev_ptr != NULL, like, don't be passing garbage bestie 🫶

and the part that ate: she implements TTL protection against infinite loops using a calculated maximum search count. so no matter how cursed the config space is, she is NOT looping forever. periodt. 💀✨

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⭐ RETURN ⭐

the position of the capability if it's found — otherwise 0. that's it, that's the vibe check 🌈

fr fr: 0 means not found, not "found at zero". don't get it twisted bestie 😭

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🦋 SEE ALSO 🦋

• Kernel file ./drivers/pci/pci.h
• PCI_FIND_NEXT_CAP(9)
• pci_bar_index_is_valid(9)
• pci_id_from_device(9)
• pci_match_one_id(9)
• pci_resource_num(9)
• pci_dev_set_io_state(9)
• struct aer_err_info(9)

like, go read those too, iykyk 📚💜

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and that's the page!! this little icon lives in ./drivers/pci and the version/date stamp says October 2026 — so yeah, she's from the future and she's still slaying 🧚‍♀️💖 mwah, ily, go find those capabilities ✨🎀