ctucan_rx(9)

💅 ctucan_rx — the Kernel API Manual page you didn't know you needed

okay so bestie, welcome to ctucan_rx(9), a real Kernel API Manual situation, and honestly? she's niche but she's iconic. let's get into it ✨

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🌸 NAME 🌸

ctucan_rx — okay so this is the function that gets called from the CAN ISR (interrupt service routine) to finish the received-frame processing. she's the closer, the finisher, the one who ties the bow on the rx frame 🎀

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✨ SYNOPSIS ✨

int ctucan_rx (struct net_device *ndev );

that's it. that's the whole vibe. one function, one pointer, no cap 💅

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🦋 ARGUMENTS 🦋

• ndev — a pointer to the net_device structure. that's her whole personality, honestly. she takes the net device and she does the thing. 🫶

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💖 DESCRIPTION 💖

so here's the tea ☕: this function gets invoked from the CAN isr (that's the poll, iykyk) to process the Rx frames.

and the way that she's so lowkey about it? she does minimal processing — like, literally the bare minimum, she's not here to overwork herself — and then she invokes netif_receive_skb to handle the rest of the processing. so she hands it off to the network layer and lets them take it from there. delegation queen 👑

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🔥 RETURN 🔥

the returns, bestie, let's break them down:

• 1 — the frame got passed along to the network layer. slay! a total win, main character energy 💖
• 0 — the first frame word was read BUT the system is temporally out of free SKBs 😭 so the code is left to resolve the SKB allocation later. not a fail, just a "we'll deal with this in a sec" moment.
• -EAGAIN — this is the case where the Rx FIFO is just... empty. nothing there. ghost town 💀

ngl, remember that 0 is not an error — it's a later problem, not a never problem. the code left to resolve the SKB allocation later handles it 🙈

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🧚 SEE ALSO 🧚

the whole friend group, the whole squad, the whole kernel file:

• Kernel file ./drivers/net/can/ctucanfd/ctucanfd_base.c
• ctucan_state_to_str(9)
• ctucan_reset(9)
• ctucan_set_btr(9)
• ctucan_set_bittiming(9)
• ctucan_set_data_bittiming(9)
• ctucan_set_secondary_sample_point(9)
• ctucan_set_mode(9)
• ctucan_chip_start(9)
• ctucan_do_set_mode(9)
• ctucan_get_tx_status(9)
• ctucan_is_txt_buf_writable(9)
• ctucan_insert_frame(9)
• ctucan_give_txtb_cmd(9)
• ctucan_start_xmit(9)
• ctucan_read_rx_frame(9)
• ctucan_read_fault_state(9)
• ctucan_get_rec_tec(9)
• ctucan_err_interrupt(9)
• ctucan_rx_poll(9)
• ctucan_rotate_txb_prio(9)
• ctucan_tx_interrupt(9)
• ctucan_interrupt(9)
• ctucan_chip_stop(9)
• ctucan_open(9)
• ctucan_close(9)
• ctucan_get_berr_counter(9)

like, that's literally the entire group chat. go read them too, they're all worth it 💜

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and that's the page, bestie!! mwah 💋 this whole thing lives in ./drivers/net/can/ctucanfd, it's dated October 2026, and it's officially known as ctucan_rx(9). catch you in the next manpage — ily, stay hydrated, and may your Rx FIFO never be empty 🍓✨