can_rcv_list_find(9)

📦 version 7.3.1, in nixpkgs unstable

💅 can_rcv_list_find(9) — the Kernel API Manual, bestie edition

okay so picture this: you're in the can subsystem, section 9 of the Kernel API Manual, and you need to know which filter list is the ✨optimal✨ one. That's this function. Her name is can_rcv_list_find and she's literally the main character of filter list picking. 🎀

✨ NAME ✨

can_rcv_list_find — determine the optimal filterlist inside the device filter struct 🦋

🌸 SYNOPSIS 🌸

struct hlist_head * can_rcv_list_find (canid_t *can_id , canid_t *mask ,
       struct can_dev_rcv_lists *dev_rcv_lists );

like, that's the whole vibe. a struct hlist_head * coming right back at you. 💫

💖 ARGUMENTS 💖

  • can_id — pointer to the CAN identifier of a given can_filter, bestie. it's a pointer, so be nice to it.
  • mask — pointer to the CAN mask of a given can_filter. also a pointer. also deserves respect. 🫶
  • dev_rcv_lists — pointer to the device filter struct. yes, another pointer. it's giving pointer party and honestly we love that for us.

🔥 DESCRIPTION 🔥

So what does she do? She returns the optimal filterlist — the whole point is to reduce the filter handling in the receive path. Less work on the hot path, more slay. 💅 This function gets called by service functions that need to register or unregister a can_filter in the filter lists. iykyk.

A filter matches, in general, when:

<received_can_id> & mask == can_id & mask

so every bit set in the mask — and yes, that includes CAN_EFF_FLAG and CAN_RTR_FLAG — describes bits that are relevant for the filter. like, those bits are the ones that actually matter. periodt. ⭐

Now the fun part, because she's flexible like that:

  • The filter can be inverted — that's the CAN_INV_FILTER bit set in can_id. 🙈
  • Or it can filter for error messages — that's the CAN_ERR_FLAG bit set in mask.

And for error msg frames there's a special filterlist and a special rx path filter handling. not like other filters. 💀✨

👑 RETURN 👑

Pointer to the optimal filterlist for the given can_id/mask pair. 🎯

Also lowkey doing extra credit on the way out:

  • Consistency checked mask.
  • Reduced can_id to have a preprocessed filter compare value.

so you get the pointer and the glow-up. no cap. 🌈

🌸 SEE ALSO 🌸

go read them, they're all iconic in their own way. 📚💜

and that's the whole page, bestie!! 🧚 this lil gem lives in ./net/can and the version/date stamp on it is October 2026, with the header can_rcv_list_find(9) riding up top the whole time. bye bestie, go register some filters responsibly 💖🍓🦋

📦 where this page comes from