debugfs_create_u64(9)

💅 debugfs_create_u64 — kernel API manual energy ✨

okay bestie, so this one is from the Kernel API Manual and it's about debugfs_create_u64, and honestly it's giving "tiny function, huge utility." no cap. 🎀

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🌸 NAME 🌸

debugfs_create_u64 — creates a debugfs file that you use to read and write an unsigned 64-bit value. literally that's its whole personality and it ate. 💖

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✨ SYNOPSIS ✨

void debugfs_create_u64 (const char *name , umode_t mode , struct dentry *parent , u64 *value );

like, that's the whole signature. keep it exactly like that, don't get creative with it, bestie. 🫶

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🦋 ARGUMENTS 🦋

• name — a pointer to a string that holds the name of the file you're creating. so like, the filename, basically. pick something cute but make it descriptive, iykyk. ✨
• mode — the permission that the file should have. yes, permissions, the thing we all respect. 💅
• parent — a pointer to the parent dentry for this file. if you're setting it, it should be a directory dentry, okay? and if this parameter is NULL, then the file gets created in the root of the debugfs filesystem. main character placement, honestly. 👑
• value — a pointer to the variable that the file should read to and write from. so like, the file is the face and value is the brain. 🧠

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🌈 DESCRIPTION 🌈

So this function creates a file in debugfs with whatever name you gave it, and that file contains the value of the variable value. Iconic behaviour. 🌟

And if the mode variable is set up that way, it can be read from, and written to. both directions. versatile. we love a dual-threat. 💜

lowkey important that if you want writing to work, mode has to actually allow it — the manpage says "if the mode variable is so set," so like, that's on you, bestie. 🙈

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🎀 SEE ALSO 🎀

Kernel file ./fs/debugfs/file.c plus the whole debugfs friend group — they all show up together, every single one, no skipping:

debugfs_file_get(9), debugfs_file_put(9), debugfs_enter_cancellation(9), debugfs_leave_cancellation(9), debugfs_create_u8(9), debugfs_create_u16(9), debugfs_create_u32(9), debugfs_create_ulong(9), debugfs_create_x8(9), debugfs_create_x16(9), debugfs_create_x32(9), debugfs_create_x64(9), debugfs_create_size_t(9), debugfs_create_atomic_t(9), debugfs_create_bool(9), debugfs_create_str(9), debugfs_create_blob(9), debugfs_create_u32_array(9), debugfs_print_regs32(9), debugfs_create_regset32(9), debugfs_create_devm_seqfile(9)

like, the whole squad. the u8/u16/u32 siblings, the x-prefix hex cousins, the atomic one, the bool one, the blob one — everybody's here. slay. 🔥

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and that's the page, bestie!! 🦋 this one's from the ./fs/debugfs source, dated October 2026, and we're out. go create some debugfs files and be iconic about it 💖✨🎀