feedback_urb_complete(9)

💖 feedback_urb_complete(9) — the kernel API manual, but make it make sense 💖

okay bestie, so today we're doing the feedback_urb_complete(9) page from the Kernel API Manual and honestly? it's kind of a big deal. this is the master clock energy of the whole driver. no cap.

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✨ NAME ✨

feedback_urb_complete — the completion handler for feedback isochronous URBs. literally what it says on the tin, and it slays.

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🌸 SYNOPSIS 🌸

void feedback_urb_complete (struct urb *urb );

that's it. that's the whole signature. cute, right? 🎀

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🦋 ARGUMENTS 🦋

• urb — the completed URB. that's the one being handed to you. it's giving "here's the finished thing, do something with it" 💅

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🔥 DESCRIPTION 🔥

okay so this function is the master clock for the driver. like, main character energy, everything else is on its schedule. lowkey iconic.

quick vibe check though: it runs in interrupt context. so be normal about it, okay? 🙈

here's the whole situation:

• it reads the feedback value from the device — that value is literally telling you how many samples the device has consumed, which is so useful of it honestly
• that info gets used to adjust the playback rate
• it also advances the capture stream pointer, so both streams stay in sync (the way they should, periodt)
• then it calls snd_pcm_period_elapsed if necessary
• and finally it resubmits itself — because of course it does, it's a completion handler, that's the whole loop 🌀

so yeah. read feedback → tune playback → nudge capture → maybe snd_pcm_period_elapsed → resubmit. and it does all of that in interrupt context. she's booked and busy. 👑

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💜 SEE ALSO 💜

the whole friend group, gathered for you 🫶:

• Kernel file ./sound/usb/usx2y/us144mkii_pcm.h
• var tascam_pcm_hw(9)
• var tascam_playback_ops(9)
• var tascam_capture_ops(9)
• playback_urb_complete(9)
• capture_urb_complete(9)
• tascam_stop_pcm_work_handler(9)
• tascam_init_pcm(9)
• us144mkii_configure_device_for_rate(9)
• process_playback_routing_us144mkii(9)
• process_capture_routing_us144mkii(9)
• tascam_pcm_hw_params(9)
• tascam_pcm_hw_free(9)
• tascam_pcm_trigger(9)
• tascam_capture_work_handler(9)

go read those too, bestie, they're all in their own little era. iykyk 💫

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and that's the page!! 🌈 this little masterpiece lives over in ./sound/usb/usx2y, dated October 2026 — so mark your calendar, screenshot it, send it to the group chat. mwah, bye 💋⭐🍓