pcm_prepare(9)

💅 pcm_prepare(9) — a Kernel API Manual moment

okay so bestie, welcome to pcm_prepare(9) from the Kernel API Manual — yes the manual name is literally part of the vibe, we're in the Kernel API Manual today and it's giving documentation excellence ✨

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🎀 NAME 🎀

pcm_prepare — the function that implements the prepare callback for the PCM middle layer. that's it. that's the whole job. iconic behaviour honestly 💖

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🦋 SYNOPSIS 🦋

int pcm_prepare (struct snd_pcm_substream *substream );

like, that's the whole signature. int in, int out, one pointer in the middle. we love a clean API 🫶

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🌸 ARGUMENTS 🌸

• substream — a substream pointer. that's literally it, that's the description, it's a pointer to a substream and we're moving on 💅

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✨ DESCRIPTION ✨

so here's the tea: this callback gets called when the PCM is "prepared" 🎀 (yes, in quotes in the original, we respect the quotes). this is your moment, your main character energy, the place where stuff like format rate, sample rate, etc. can be set. slay.

and the way that it can be called many times at each setup? yeah. it's not a one-and-done situation, it's a "see you again next setup" situation. lowkey relatable. 🔁

returns 0 on success, or an error code otherwise. no cap, that's the contract — succeed with a 0 or throw hands with an error code 😭

ngl bestie, if you're not returning 0 on the good path, the vibe check has failed. error codes otherwise. periodt.

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🔥 SEE ALSO 🔥

okay this list is LONG and honestly it ate, so let's go through it:

• Kernel file ./drivers/most/most_snd.c — the actual file, go read it, iykyk 📖
• struct channel(9)
• get_channel(9)
• copy_data(9)
• playback_thread(9)
• pcm_open(9)
• pcm_close(9)
• pcm_trigger(9)
• pcm_pointer(9)
• audio_probe_channel(9)
• audio_disconnect_channel(9)
• audio_rx_completion(9)
• audio_tx_completion(9)

that's thirteen references bestie, thirteen. we are FED tonight 🍓

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💜 the cute sign-off 💜

this little page lives in ./drivers/most, it's dated October 2026, and it answers to the name pcm_prepare(9). go forth and prepare your PCMs, you absolute icon 👑💖