async_gen_syndrome(9)

💖 NAME 💖

async_gen_syndrome — asynchronously calculate a raid6 syndrome

okay so hi bestie, this is the async_gen_syndrome(9) page from the Kernel API Manual — yes, that manual, and yes, we’re doing kernel math with main-character energy. ✨

✨ SYNOPSIS ✨

struct dma_async_tx_descriptor * async_gen_syndrome (struct page
       **blocks , unsigned int *offsets , int disks , size_t len , struct
       async_submit_ctl *submit );

🎀 ARGUMENTS 🎀

• blocks — source blocks from idx 0..disks-3, P at disks-2, and Q at disks-1.
• offsets — offset array into each block (src and dest) to start transaction.
• disks — number of blocks (including missing P or Q, see below).
• len — length of operation in bytes.
• submit — submission/completion modifiers.

🦋 DESCRIPTION 🦋

General note, and this is important math lore: this routine assumes a field of GF(2^8) with a primitive polynomial of 0x11d and a generator of {02}. 🧚

The page picks up mid-thought here, so I’m keeping the exact fragment: “both) from the calculation by setting blocks[disks-2] or blocks[disks-1] to NULL.”

💀 Bestie, when P or Q is omitted, len must be <= PAGE_SIZE, because a temporary buffer of this size is used in the synchronous path. No cap.

disks always accounts for both destination buffers.

If any source buffers (blocks[i] where i < disks - 2) are set to NULL, those buffers will be replaced with the raid6_zero_page in the synchronous path and omitted in the hardware-asynchronous path. Slay, but carefully. 💅

🌈 SEE ALSO 🌈

• Kernel file ./crypto/async_tx/async_pq.c — go read it, bestie.
• async_syndrome_val(9) — another reference, iykyk.

kisses and kernel dust 💅🫶 — this page lives in ./crypto/async_tx, dated October 2026, and it’s the async_gen_syndrome(9) glow-up. periodt. 🎀