sysfs_bin_attr_simple_read(9)

📦 version 7.3.1, in nixpkgs unstable

💅 sysfs_bin_attr_simple_read 💅

okay bestie, so this is a page from the Kernel API Manual — it's sysfs_bin_attr_simple_read(9), and no, the name is not a vibe, it's literally what it does. Let's get into it ✨

🌸 NAME 🌸

sysfs_bin_attr_simple_read — the read callback that literally just copies stuff from memory. no thoughts, just bytes 🔥

🦋 SYNOPSIS 🦋

ssize_t sysfs_bin_attr_simple_read (struct file *file , struct kobject
       *kobj , const struct bin_attribute *attr , char *buf , loff_t off ,
       size_t count );

six arguments, one function, zero drama (mostly 😌).

🎀 ARGUMENTS 🎀

  • file — the attribute file that's being read rn. it's giving "the main character of this read operation" 👑
  • kobj — the object this attribute belongs to. its whole squad, basically 🫶
  • attr — the attribute descriptor. the lil ID card for the attribute 💳
  • buf — the destination buffer. this is where the bytes are gonna land, so be nice to it 💖
  • off — offset in bytes from which to read. like a bookmark, but for memory 📖
  • count — the maximum number of bytes to read. the absolute ceiling, the limit, the "that's enough" 🛑

✨ DESCRIPTION ✨

So this is the simple ->read callback for bin_attributes that are backed by a buffer in memory. lowkey the whole point: it copies from memory to buf, and that's it. iconic behavior, no notes 💅

⚠️ IMPORTANT SETUP STEP, DO NOT SKIP — before the bin_attribute is created in sysfs, you must set the private and size members in struct bin_attribute to the buffer's location and size. If you don't, it's giving chaos, not cute 🙈

The bounds check for off and count happens in sysfs_kf_bin_read — so that's not this function's job, bestie, it's already handled elsewhere fr fr. and the negative value check for off? that goes down in vfs_setpos and default_llseek. so like, three separate places are doing vibe checks so this callback can stay in its simple era 🌈

Returns the number of bytes written to buf. that's the whole return value. periodt 💜

🧚 SEE ALSO 🧚

Kernel file ./fs/sysfs/file.c — plus the whole friend group, all of these have their own manual pages:

like, read them, they're all slay in their own way 📚💖

and that's the whole page, bestie!! this one lives in ./fs/sysfs and it's dated October 2026 — future vibes only ⭐🦋 thank you for coming to my ted talk, now go set those private and size members before you create anything 💀💅

📦 where this page comes from