dax_direct_access(9)

✨ dax_direct_access 💫

okay so first things first, this page lives in the Kernel API Manual section (that's section 9, bestie, the kernel-API one, not the "type man and pray" one) and it's literally all about translating a device pgoff into an absolute pfn. icon behavior honestly 🎀

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🌸 NAME 🌸

dax_direct_access — translate a device pgoff to an absolute pfn ✨

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🦋 SYNOPSIS 🦋

long dax_direct_access (struct dax_device *dax_dev , pgoff_t pgoff ,
long nr_pages , enum dax_access_mode mode , void **kaddr , unsigned long
*pfn );

she takes six arguments and returns a long, no cap 💅

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💖 ARGUMENTS 💖

• dax_dev — a dax_device instance that represents the logical memory range. like, this is the device we're talking about, she's the main character 👑
• pgoff — the offset in pages, counted from the start of the device, that you want translated 🧚
• nr_pages — how many consecutive pages the caller can handle relative to pfn. so, how much you're ready to take in one go 🫶
• mode — an indicator of whether this is a normal access or a recovery write ⭐
• kaddr — output parameter that returns a virtual address mapping of pfn 🎀
• pfn — output parameter that returns an absolute pfn translation of pgoff 🔥

bestie note: kaddr and pfn are output parameters, so they're giving results back to you, they are not input, don't come for them 🙈

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🌈 RETURN 🌈

• a negative errno if an error occurs 😭
• otherwise, the number of pages accessible at the device relative pgoff ✨

like, either it's a sad negative number or it's a page count. no in-between, periodt 💀

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💜 SEE ALSO 💜

• Kernel file ./drivers/dax/super.c
• struct dax_device(9)
• fs_dax_get_by_bdev(9)
• fs_put_dax(9)
• fs_dax_get(9)
• dax_set_ops(9)
• dax_holder(9)
• inode_dax(9)

go read those next, iykyk 📚✨

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lowkey this whole thing lives under ./drivers/dax, the page is dated October 2026, and it's dax_direct_access(9) all the way down — that's the vibe check, we're done here 💅🫶🍓