pci_iomap_wc(9)

✨ pci_iomap_wc(9) ✨

okay so real talk, this is a page from the Kernel API Manual and honestly? it's a whole vibe. bestie, we're making a virtual WC mapping cookie for a PCI BAR today. no cap. 🍓

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🌸 NAME 🌸

pci_iomap_wc — create a virtual WC mapping cookie for a PCI BAR 💅

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🦋 SYNOPSIS 🦋

void __iomem * pci_iomap_wc (struct pci_dev *dev , int bar , unsigned
long maxlen );

like, that's the whole signature. slay. ✨

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🎀 ARGUMENTS 🎀

• dev — the PCI device that owns the BAR. it's her BAR, she's the main character 👑
• bar — the BAR number. just a number. iconic. 🔥
• maxlen — length of the memory to map. the size of the vibe check, basically 🦋

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💖 DESCRIPTION 💖

so when you use this function you get a __iomem address to your device BAR. that's the gift. 🎁

you can access it using ioread*() and iowrite*(). these functions are lowkey the best because they hide the details of whether this is a MMIO or PIO address space, and they'll just do what you expect from them in the correct way. no notes. literally perfect behavior. ✨ when possible, write combining is used. 😌

maxlen specifies the maximum length to map. and here's the cute shortcut: if you want to get access to the complete BAR without checking for its length first, just pass 0 here. zero. that's it. that's the move. 🫶

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🌈 SEE ALSO 🌈

• Kernel file ./drivers/pci/iomap.c
• pci_iomap_range(9)
• pci_iomap_wc_range(9)
• pci_iomap(9)

go read them, iykyk 💜

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fr fr bestie, this one's from ./drivers/pci, dated October 2026. periodt. 💀✨🎀