pdc_send_data(9)

💌 pdc_send_data — the Kernel API Manual glow-up ✨

okay so bestie, welcome to pdc_send_data(9) — literally the page from the Kernel API Manual and it's all about that mailbox life 🫶

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✨ NAME ✨

pdc_send_data — the mailbox send_data function, no cap 💅

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🌸 SYNOPSIS 🌸

int pdc_send_data (struct mbox_chan *chan , void *data );

that's it. that's the whole vibe. two args, one int back at ya 🎀

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🦋 ARGUMENTS 🦋

• chan — the mailbox channel where the data gets sent, okay? and like, this channel corresponds to a DMA ringset. iykyk 💫
• data — the actual mailbox message being sent. Important: the message must be a brcm_message structure. not optional, bestie, it's giving strict 😭

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💖 DESCRIPTION 💖

so here's the tea ☕ — this function is registered as the send_data function for the mailbox controller. main character energy fr.

what it does, step by step, because the way that this works is iconic:

1. from the destination scatterlist in the mailbox message, it creates a sequence of receive descriptors in the rx ring 🌈
2. from the source scatterlist, it creates a sequence of transmit descriptors in the tx ring 🦋
3. after creating all those descriptors, it writes the rx ptr and tx ptr registers to initiate the DMA transfer 🔥

and that's not even all of it — this function also does the DMA map and unmap of the src and dst scatterlists in the mailbox message. doing the most, honestly 👑

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⭐ RETURN ⭐

• 0 — slayed, it worked, successful 💅
• -ENOTSUPP — the mailbox message is a type this driver does not support, so... yeah, not supported 🙈
• < 0 — an error happened, that's a mood killer for real 😭

ngl bestie, pay attention to the < 0 case — that's the generic "something went wrong" bucket and you don't want to be in it.

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🔮 SEE ALSO 🔮

Kernel file ./drivers/mailbox/bcm-pdc-mailbox.c — and honestly the whole friend group shows up here:

pdc_setup_debugfs(9), pdc_build_rxd(9), pdc_build_txd(9), pdc_receive_one(9), pdc_receive(9), pdc_tx_list_sg_add(9), pdc_tx_list_final(9), pdc_rx_list_init(9), pdc_rx_list_sg_add(9), pdc_irq_handler(9), pdc_work_cb(9), pdc_ring_init(9), pdc_desc_count(9), pdc_rings_full(9), pdc_last_tx_done(9), pdc_hw_init(9), pdc_hw_disable(9), pdc_rx_buf_pool_create(9), pdc_interrupts_init(9), pdc_mb_init(9), pdc_dt_read(9), pdc_probe(9)

like... the whole squad. go read them too, bestie 🫶

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and that's the page!! sourced from ./drivers/mailbox, dated October 2026, and it's the pdc_send_data(9) era 🌸✨ bye bestie, go build some descriptors 💜