IDA DESCRIPTION(9)

💖 IDA description 💖

okay bestie, this is the IDA description page from the Kernel API Manual, section 9 — and it’s giving tiny but mighty allocator energy. ✨

So the IDA is an ID allocator, and the big thing it does not do is give you the ability to associate an ID with a pointer. Because of that, it only needs to store one bit per ID — literally one bit — so it’s more space efficient than an IDR. Memory queen behavior, fr fr. 👑

To use an IDA, define it using DEFINE_IDA (or embed a struct ida in a data structure, then initialise it using ida_init). To allocate a new ID, call ida_alloc, ida_alloc_min, ida_alloc_max or ida_alloc_range. To free an ID, call ida_free. Slay. 💅

ida_destroy can be used to dispose of an IDA without needing to free the individual IDs in it. You can use ida_is_empty to find out whether the IDA has any IDs currently allocated. Cute and useful. 🎀

The IDA handles its own locking. It is safe to call any of the IDA functions without synchronisation in your code. No cap — no extra lock choreography needed in your code. 🔒✨

IDs are currently limited to the range [0-INT_MAX]. If this is an awkward limitation, it should be quite straightforward to raise the maximum.

🦋 SEE ALSO 🦋

Kernel file ./lib/idr.c and the whole reference squad:

• idr_alloc_u32(9)
• idr_alloc(9)
• idr_alloc_cyclic(9)
• idr_remove(9)
• idr_find(9)
• idr_for_each(9)
• idr_get_next_ul(9)
• idr_get_next(9)
• idr_replace(9)
• ida_alloc_range(9)
• ida_find_first_range(9)
• ida_free(9)
• ida_destroy(9)

okay bye bestie 💖 mwah — source/version: ./lib; date: October 2026. 🫶🌸