mbox_request_channel(9)

💌 mbox_request_channel(9) — like, the whole kernel API manual moment

Okay bestie, so this one's a kernel API manual page, and it's literally called mbox_request_channel — yes, we're requesting a mailbox channel, and no, it's not about your Gmail 🌸

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✨ NAME ✨

mbox_request_channel — request a mailbox channel 🎀

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🦋 SYNOPSIS 🦋

struct mbox_chan * mbox_request_channel (struct mbox_client *cl , int
index );

That's the whole vibe: you hand it a client, you hand it an index, you get back a struct mbox_chan *. Iconic signature, no notes 💅

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🍓 ARGUMENTS 🍓

• cl — the identity of the client that's requesting the channel. It's giving "hi, it's me, I'm the one asking" 🫶
• index — the index of the mailbox specifier in the 'mboxes' property. Lowkey just the position number, iykyk.

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💖 DESCRIPTION 💖

So here's the tea: the client specifies its requirements and its capabilities while it's asking for a mailbox channel. Both. At the same time. Multitasking main character energy ✨

🚨 Big warning, bestie: it can't be called from atomic context. Not negotiable. Do not try it. The kernel will not be cute about it.

The channel is exclusively allocated — meaning it literally can't be used by another client before the owner calls mbox_free_channel. One owner, one channel, periodt 👑

After assignment, any packet received on this channel will be handed over to the client via the 'rx_callback'. So the data just shows up at your door like a little delivery 🎁

And this part matters: the framework holds a reference to the client, so the mbox_client structure shouldn't be modified until mbox_free_channel returns. Fr fr, don't touch it. Leave it alone. Let it cook 😭

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🔥 RETURN 🔥

• Pointer to the channel assigned to the client — that's the success case, slay 💜
• ERR_PTR — that's for request failure, so check for it, ngl 🙈

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🌈 SEE ALSO 🌈

Kernel file ./drivers/mailbox/mailbox.c, plus the whole friend group:

• mbox_chan_received_data(9)
• mbox_chan_txdone(9)
• mbox_client_txdone(9)
• mbox_client_peek_data(9)
• mbox_chan_tx_slots_available(9)
• mbox_send_message(9)
• mbox_flush(9)
• mbox_bind_client(9)
• mbox_free_channel(9)
• mbox_controller_register(9)
• mbox_controller_unregister(9)
• devm_mbox_controller_register(9)

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And that's the page, bestie 🧚💫 Signing off from ./drivers/mailbox, in the Kernel API Manual, dated October 2026 — go request your channel, you've got this, no cap 💅🎀🦋