spu2_ctx_max_payload(9)

🦋 spu2_ctx_max_payload(9) — a Kernel API Manual moment

okay so bestie, welcome to the Kernel API Manual, where today's main character is spu2_ctx_max_payload 💅 like yes we're doing kernel crypto documentation and yes it's iconic.

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✨ NAME ✨

spu2_ctx_max_payload — literally just figures out the maximum length of the payload for a SPU message, for a given cipher and hash alg context 🎀

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🌸 SYNOPSIS 🌸

u32 spu2_ctx_max_payload (enum spu_cipher_alg cipher_alg , enum
spu_cipher_mode cipher_mode , unsigned int blocksize );

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💖 ARGUMENTS 💖

• cipher_alg — the cipher algorithm, the vibe of the cipher basically 🔥
• cipher_mode — the cipher mode, like which mode it's in
• blocksize — the size of a block of data for this algo, no cap

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👑 DESCRIPTION 👑

so here's the tea for SPU2 ☕ the hardware generally ignores the PayloadLen field in ctrl3 of FMD and just keeps computing until it receives a DMA descriptor with the EOF flag set. it's giving "I'll stop when I feel like it" energy honestly 😭

so because of that, we consider the max payload to be infinite 🌈 like, boundless, no ceiling, infinite scroll but make it hardware.

but wait — AES CCM is an exception 🚨 don't forget the exception bestie, it's the one that breaks the pattern.

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⭐ RETURN ⭐

Max payload length in bytes 💖 that's the whole answer, she said what she said.

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🎀 SEE ALSO 🎀

Kernel file ./drivers/crypto/bcm/spu2.c — and honestly the whole friend group is here, say hi to everyone 🫶

• spu2_cipher_xlate(9)
• spu2_hash_xlate(9)
• spu2_fmd_init(9)
• spu2_fmd_ctrl0_write(9)
• spu2_fmd_ctrl1_write(9)
• spu2_fmd_ctrl2_write(9)
• spu2_fmd_ctrl3_write(9)
• spu2_payload_length(9)
• spu2_response_hdr_len(9)
• spu2_hash_pad_len(9)
• spu2_gcm_ccm_pad_len(9)
• spu2_assoc_resp_len(9)
• spu2_aead_ivlen(9)
• spu2_hash_type(9)
• spu2_digest_size(9)
• spu2_create_request(9)
• spu2_cipher_req_init(9)
• spu2_cipher_req_finish(9)
• spu2_request_pad(9)
• spu2_xts_tweak_in_payload(9)
• spu2_tx_status_len(9)
• spu2_rx_status_len(9)
• spu2_status_process(9)
• spu2_ccm_update_iv(9)
• spu2_wordalign_padlen(9)

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that's the page bestie, go read your kernel source 💜

sign-off szn 🎀 this one lives in ./drivers/crypto/bcm, dated October 2026, and it's the spu2_ctx_max_payload(9) page from the Kernel API Manual — slay, mwah 💋