STRUCT ONENAND_CHIP(9)

💖 NAME

struct onenand_chip — the OneNAND Private Flash Chip Data, aka the one struct that holds literally everything the kernel needs to gossip with your OneNAND flash chip 💅

okay so real quick before we dive in: this page lives in the Kernel API Manual and it is genuinely giving "one struct to hold the whole entire chip" energy. it ate. it's iconic. periodt. 🎀

✨ SYNOPSIS

struct onenand_chip {
    void __iomem            *base;
    unsigned dies;
    unsigned boundary[MAX_DIES];
    loff_t diesize[MAX_DIES];
    unsigned int            chipsize;
    unsigned int            device_id;
    unsigned int            version_id;
    unsigned int            technology;
    unsigned int            density_mask;
    unsigned int            options;
    unsigned int            badblockpos;
    unsigned int            erase_shift;
    unsigned int            page_shift;
    unsigned int            page_mask;
    unsigned int            writesize;
    unsigned int            bufferram_index;
    struct onenand_bufferram        bufferram[MAX_BUFFERRAM];
    int (*command)(struct mtd_info *mtd, int cmd, loff_t address, size_t len);
    int (*wait)(struct mtd_info *mtd, int state);
    int (*bbt_wait)(struct mtd_info *mtd, int state);
    void (*unlock_all)(struct mtd_info *mtd);
    int (*read_bufferram)(struct mtd_info *mtd, int area, unsigned char *buffer, int offset, size_t count);
    int (*write_bufferram)(struct mtd_info *mtd, int area, const unsigned char *buffer, int offset, size_t count);
    unsigned short (*read_word)(void __iomem *addr);
    void (*write_word)(unsigned short value, void __iomem *addr);
    void (*mmcontrol)(struct mtd_info *mtd, int sync_read);
    int (*chip_probe)(struct mtd_info *mtd);
    int (*block_markbad)(struct mtd_info *mtd, loff_t ofs);
    int (*scan_bbt)(struct mtd_info *mtd);
    int (*enable)(struct mtd_info *mtd);
    int (*disable)(struct mtd_info *mtd);
    struct completion       complete;
    int irq;
    spinlock_t chip_lock;
    wait_queue_head_t wq;
    flstate_t state;
    unsigned char           *page_buf;
    unsigned char           *oob_buf;
  #ifdef CONFIG_MTD_ONENAND_VERIFY_WRITE;
    unsigned char           *verify_buf;
  #endif;
    int subpagesize;
    void *bbm;
    void *priv;
    unsigned int            ongoing;
};

lowkey look at all those function pointers 😭 the struct is basically a whole personality made of callbacks 🦋

🌸 MEMBERS

btw if you're wondering what those lil bracketed tags mean, they're the vibe check on each member — [INTERN], [BOARDSPECIFIC], [REPLACEABLE], [OPTIONAL], and [INTERN][FLEX-ONENAND] for the Flex-OneNAND-specific ones. they tell you who's allowed to touch it, iykyk 👑

• base — [BOARDSPECIFIC] the address you use to access OneNAND
• dies — [INTERN][FLEX-ONENAND] how many dies are on the chip
• boundary — [INTERN][FLEX-ONENAND] the boundary of the dies
• diesize — [INTERN][FLEX-ONENAND] the size of the dies
• chipsize — [INTERN] the size of one chip for multichip arrays. there's a straight-up FIXME here: for Flex-OneNAND, chipsize holds the maximum possible device size, i.e. when all blocks are considered MLC 🫠
• device_id — [INTERN] the device ID
• density_mask — chip density, used for DDP devices
• options — [BOARDSPECIFIC] various chip options. they can partly be set to inform onenand_scan about stuff
• erase_shift — [INTERN] number of address bits in a block
• page_shift — [INTERN] number of address bits in a page
• page_mask — [INTERN] a page per block mask
• writesize — [INTERN] a real page size
• bufferram_index — [INTERN] BufferRAM index
• bufferram — [INTERN] BufferRAM info
• command — [REPLACEABLE] hardware specific function for writing commands to the chip
• wait — [REPLACEABLE] hardware specific function for wait on ready
• bbt_wait — [REPLACEABLE] hardware specific function for bbt wait on ready
• unlock_all — [REPLACEABLE] hardware specific function for unlock all
• read_bufferram — [REPLACEABLE] hardware specific function for BufferRAM Area
• write_bufferram — [REPLACEABLE] hardware specific function for BufferRAM Area
• read_word — [REPLACEABLE] hardware specific function for read register of OneNAND
• write_word — [REPLACEABLE] hardware specific function for write register of OneNAND
• mmcontrol — sync burst read function
• chip_probe — [REPLACEABLE] hardware specific function for chip probe
• block_markbad — function to mark a block as bad
• scan_bbt — [REPLACEALBE] hardware specific function for scanning Bad block Table (and yes, that spelling is straight from the source, bestie — we don't edit the source, we respect the source 💀)
• chip_lock — [INTERN] spinlock used to protect access to this structure and the chip
• wq — [INTERN] wait queue to sleep on if a OneNAND operation is in progress
• state — [INTERN] the current state of the OneNAND device
• page_buf — [INTERN] page main data buffer
• oob_buf — [INTERN] page oob data buffer
• subpagesize — [INTERN] holds the subpagesize
• bbm — [REPLACEABLE] pointer to Bad Block Management
• priv — [OPTIONAL] pointer to private chip date

ngl a couple of the fields up in the struct above don't get their own lil blurb in this Members list — version_id, technology, badblockpos, enable, disable, complete, irq and ongoing are just out here living their lives. that's not me gatekeeping, that's literally how the page is written 🙈

🦋 SEE ALSO

• Kernel file ./include/linux/mtd/onenand.h
• struct onenand_bufferram(9)
• struct onenand_manufacturers(9)

go read those next, bestie, the lore goes deep 🌈

and that's the whole page!! this lil rewrite came to you from the Kernel API Manual, sourced from ./include/linux/mtd, dated October 2026 🫶 stay hydrated, back up your flash, and don't forget to #ifdef your verify_buf 💜✨