aac_biosparm(9)

📦 version 7.3.1, in nixpkgs unstable

💾 aac_biosparm(9) — the Kernel API Manual, bestie edition 🎀

okay so picture this: it's a page from the Kernel API Manual, and it's here to spill the tea on aac_biosparm. yes, the name is giving "silent but essential kernel helper energy" and honestly? we're obsessed. 💅

✨ NAME ✨

aac_biosparm — returns BIOS parameters for a disk, that's the whole vibe 🌸

🦋 SYNOPSIS 🦋

int aac_biosparm (struct scsi_device *sdev , struct gendisk *disk ,
sector_t capacity , int *geom );

literally the whole signature, no cap. four args, one int back. 👑

💖 ARGUMENTS 💖

  • sdev — the scsi device that corresponds to the disk. your main character scsi device, fr fr.
  • disk — the gendisk that corresponds to the disk. yes bestie, they're both "the disk", that's just how it is. 🙈
  • capacity — the sector capacity of the disk. it's a sector_t, it's big, it's iconic.
  • geom — the geometry block to fill in. this one gets written to, so handle with care 🫶

🔥 DESCRIPTION 🔥

so what does it actually do? it returns the Heads/Sectors/Cylinders BIOS Disk Parameters for the Disk. that's the whole assignment. ✨

the default disk geometry is 64 heads, 32 sectors, and the appropriate number of cylinders so as not to exceed drive capacity. cute, classic, reliable. 🎀

now here's where it gets spicy 🌶️ — for disks equal to or larger than 1 GB to be addressable by the BIOS without exceeding the BIOS limitation of 1024 cylinders, Extended Translation should be enabled. iykyk.

and when Extended Translation is enabled, the geometry glow-up goes like this:

  • drives between 1 GB inclusive and 2 GB exclusive are given a disk geometry of 128 heads and 32 sectors 🦋
  • drives above 2 GB inclusive are given a disk geometry of 255 heads and 63 sectors 👑
⚠️ okay but listen — if the BIOS detects that the Extended Translation setting does not match the geometry in the partition table, then the translation inferred from the partition table will be used by the BIOS, and a warning may be displayed. so like… the tables can turn. drama. 😭

🌈 SEE ALSO 🌈

kernel file ./drivers/scsi/aacraid/linit.c plus the whole friend group:

go read them, they're all slay in their own way 💜

and that's the page!! brought to you by ./drivers/scsi/aacraid (the source, the moment, the icon) — October 2026 edition, from the Kernel API Manual itself. mwah 💋 stay geometric bestie 🧚‍♀️💫

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