doc_ecc_bch_fix_data(9)

💖 doc_ecc_bch_fix_data(9) — like, the Kernel API Manual's glow-up edition ✨

okay so bestie, sit down, hydrate, and let me tell you about doc_ecc_bch_fix_data — it's a function from the Kernel API Manual, section 9, and honestly? it's giving "tiny function, huge responsibility." 💅

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🌸 NAME 🌸

doc_ecc_bch_fix_data — literally just "Fix if need be read data from flash." that's the whole job. it reads, it checks, it fixes. main character energy fr fr 🎀

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✨ SYNOPSIS ✨

int doc_ecc_bch_fix_data (struct docg3 *docg3 , void *buf , u8 *hwecc );

three args, one int coming back at you. simple. iconic. no notes. 🦋

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🫶 ARGUMENTS 🫶

• docg3 — the device 💜 like, the actual flash chip you're working with, no cap.
• buf — the buffer of read data. and bestie, it's exactly 512 + 7 + 1 bytes, okay? don't come at it with any other size, i'm begging 🙈
• hwecc — the hardware calculated ECC. and here's the tea 🍵: it's in fact recv_ecc ^ calc_ecc, where recv_ecc was read from OOB area data, and calc_ecc is the ECC calculated by the hardware generator. so it's a XOR of two ECCs. that's the whole vibe. ⭐

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🔥 DESCRIPTION 🔥

so what does it actually do? it checks if the received data matches the ECC, and if an error gets detected, it tries to fix the bit flips — at most 4 of them, periodt — right there in the buffer buf. 🩹✨

and now the spicy part 🌶️: the docg3 understands the (data, ecc, syndroms) in an inverted order compared to the BCH library. so the function reverses the order of bits — ie. bit7 and bit0, bit6 and bit 1, ... — for all ECC data. it's literally just flipping the whole thing around. gymnastics but for bits. 🤸‍♀️

the hardware ecc unit produces oob_ecc ^ calc_ecc. the kernel's bch algorithm is used to decode this. however the hw operates on page data in a bit order that is the reverse of that of the bch alg, requiring that the bits be reversed on the result. and credit where it's due: thanks to Ivan Djelic for his analysis. 👑 respect the icon, iykyk.

returns the number of fixed bits (0, 1, 2, 3, 4) — or -EBADMSG if too many bit errors were detected and cannot be fixed. 😭 like if it's just Too Much, you get the error, no pretending otherwise. 💀

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🌈 SEE ALSO 🌈

the whole squad, and yes we're listing all of them because every single one is part of the lore 🧚:

kernel file ./drivers/mtd/devices/docg3.c, plus doc_delay(9), doc_read_data_area(9), doc_write_data_area(9), doc_set_reliable_mode(9), doc_set_asic_mode(9), doc_set_device_id(9), doc_set_extra_page_mode(9), doc_setup_addr_sector(9), doc_setup_writeaddr_sector(9), doc_read_seek(9), doc_write_seek(9), doc_read_page_ecc_init(9), doc_write_page_ecc_init(9), doc_ecc_disable(9), doc_hamming_ecc_init(9), doc_read_page_prepare(9), doc_read_page_getbytes(9), doc_write_page_putbytes(9), doc_get_bch_hw_ecc(9), doc_page_finish(9), doc_read_page_finish(9), calc_block_sector(9), doc_read_oob(9), doc_block_isbad(9), doc_get_erase_count(9), doc_get_op_status(9), doc_write_erase_wait_status(9), doc_erase_block(9), doc_erase(9), doc_write_page(9), doc_guess_autoecc(9), doc_fill_autooob(9), doc_backup_oob(9), doc_write_oob(9), doc_set_driver_info(9), doc_probe_device(9), doc_release_device(9), docg3_resume(9), docg3_suspend(9), docg3_probe(9), docg3_release(9).

like... that's a lot of friends and they all ate. 💖

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and that's the page bestie! 🎀 brought to you by the fine folks at ./drivers/mtd/devices, dated October 2026, living rent-free in the Kernel API Manual, section 9. mwah 💋 go fix some bits, you've got this 🦋✨