lpfc_idiag_pcicfg_read(9)

📦 version 7.3.1, in nixpkgs unstable

💅 lpfc_idiag_pcicfg_read(9) — the idiag debugfs read pcicfg girlie ✨

okay bestie, so this one lives in the Kernel API Manual (section 9, the kernel-functions club 🎀) and honestly? it's giving "peek at the hardware's paperwork." let's get into it.

🌸 SYNOPSIS 🌸

ssize_t lpfc_idiag_pcicfg_read (struct file *file , char __user *buf ,
       size_t nbytes , loff_t *ppos );

that's the whole signature, no notes, copy it exactly bestie 💅

🦋 ARGUMENTS 🦋

  • file — the file pointer we're reading from. like, the actual file object you're coming in through, y'know?
  • buf — the buffer where the data gets copied to. it's a char __user * so yes it lives in userspace, be normal about it 🫶
  • nbytes — how many bytes you're asking for. the count. the vibe. the limit.
  • ppos — the position in the file where reading starts. the little bookmark 📖

✨ DESCRIPTION ✨

so what this routine does is it reads data from the phba PCI config space — following whatever the idiag command told it to do — and then copies it all out to the user buf. simple enough, right? 💖

but here's the fun part, because depending on how the PCI config space read command was set up, it will do one of these:

  • a single register read of a byte (8 bits), or
  • a single register read of a word (16 bits), or
  • a single register read of a dword (32 bits), or
  • literally browse through all the registers from the 4K extended PCI config space 👑

that's it, that's the whole mood. it's either one little scoop or the entire buffet, no in-between 🍓

💜 RETURN 💜

this function returns the amount of data that was actually read — and heads up, that could be less than nbytes if the end of the file was reached 😭 — or a negative error value if something went sideways. no cap, check your return values.

🌈 SEE ALSO 🌈

the kernel file, for the curious:

Kernel file ./drivers/scsi/lpfc/lpfc_debugfs.c

and now the whole friend group, everybody say hi 👋 (yes, all of them, we're not skipping anyone, that's not the energy here):

like, the whole roster. iconic behavior honestly 👑

and that's the page!! 🌸 sourced from ./drivers/scsi/lpfc, this drop is dated October 2026 — so future-coded of it. mwah, go read some PCI config space bestie, drink water, and remember: the return value might be shorter than you asked for 💖✨🎀

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