STRUCT HWRNG(9)

💖 struct hwrng(9) 💖

okay so bestie, welcome to the struct hwrng page from the Kernel API Manual — yes, that's the Hardware Random Number Generator driver, and yes it's exactly as iconic as it sounds 🔥

This is the struct you fill out when you want your lil hardware entropy source to be a main character in the kernel. Every field, every callback, every vibe — all here 👑

✨ SYNOPSIS ✨

struct hwrng {
    const char *name;
    int (*init)(struct hwrng *rng);
    void (*cleanup)(struct hwrng *rng);
    int (*data_present)(struct hwrng *rng, int wait);
    int (*data_read)(struct hwrng *rng, u32 *data);
    int (*read)(struct hwrng *rng, void *data, size_t max, bool wait);
    unsigned long priv;
    unsigned short quality;
 };

🎀 Members 🎀

okay so let's go field by field, no skipping, periodt 💅

• name — the unique RNG name. like a name name, there can only be one, so pick something cute and unique 🦋
• init — the initialization callback. can be NULL, no pressure 🫶
• cleanup — the cleanup callback. also can be NULL, we love an optional bestie ✨
• data_present — callback that figures out if there's data available on the RNG. if it's NULL, it's assumed there's always data available. *OBSOLETE* 👀 — yeah she's deprecated, noted 💀
• data_read — read data from the RNG device. returns the number of lower random bytes in "data". must not be NULL. also *OBSOLETE* 😭 — yep, legacy behavior
• read — the new API, this is the glow-up 😌 drivers can fill up to max bytes of data into the buffer. the buffer is aligned for any type, and max is a multiple of 4 and >= 32 bytes. write that down, it matters 🎀
• priv — private data, for use by the RNG driver only. your personal little stash, iykyk 🙈
• quality — estimation of true entropy in the RNG's bitstream, in bits of entropy per 1024 bits of input. valid values: 1 to 1024, or 0 for maximum. do not mess this up, it's literally the whole vibe check for your entropy ⭐

🌈 SEE ALSO 🌈

• Kernel file ./include/linux/hw_random.h — go read it, bestie, it's giving source of truth 💜

okay that's the whole page, you ate that up 👑 sign-off time: this is from ./include/linux, version October 2026, and the page is literally struct hwrng(9). slay, go write a hardware RNG driver 💖🧚🌸