snd_devm_card_new(9)

📦 version 7.3.1, in nixpkgs unstable

okay bestie 💖 welcome to the snd_devm_card_new(9) page from the Kernel API Manual — section 9, kernel API edition. this one is all about making a managed snd_card object, and yes it’s giving “let devres handle the cleanup” energy ✨

NAME 🎀

snd_devm_card_new — managed snd_card object creation.

SYNOPSIS ✨

int snd_devm_card_new (struct device *parent , int idx , const char *xid
, struct module *module , size_t extra_size , struct snd_card **card_ret
);

ARGUMENTS 🫶

parent — the parent device object.
idx — card index (address), and the range is [0 ... (SNDRV_CARDS-1)].
xid — card identification (ASCII string).
module — top level module for locking.
extra_size — allocate this extra size after the main soundcard structure.
card_ret — the pointer to store the created card instance.

DESCRIPTION 💅

This function works like snd_card_new, but it manages the allocated resource via devres, i.e. you don’t need to free explicitly. literally the whole point, and it ate.

When a snd_card object is created with this function and registered via snd_card_register, the very first devres action to call snd_card_free is added automatically. In that way, the resource disconnection is assured at first, then released in the expected order. no cap, that ordering matters.

⚠️ bestie, listen: if an error happens at the probe before snd_card_register is called and there have been other devres resources, you’d need to free the card manually via snd_card_free call in the error; otherwise it may lead to UAF due to devres call orders. You can use snd_card_free_on_error helper for handling it more easily. this is the “please don’t rawdog the error path” warning 🫶

RETURN 🌈

zero if successful, or a negative error code.