sound/usb/usx2y/us144mkii_pcm.h

Source file repositories/reference/linux-study-clean/sound/usb/usx2y/us144mkii_pcm.h

File Facts

System
Linux kernel
Corpus path
sound/usb/usx2y/us144mkii_pcm.h
Extension
.h
Size
5954 bytes
Lines
166
Domain
Driver Families
Bucket
sound/usb
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

// Copyright (c) 2025 Šerif Rami <ramiserifpersia@gmail.com>

#ifndef __US144MKII_PCM_H
#define __US144MKII_PCM_H

#include "us144mkii.h"

/**
 * tascam_pcm_hw - Hardware capabilities for TASCAM US-144MKII PCM.
 *
 * Defines the supported PCM formats, rates, channels, and buffer/period sizes
 * for the TASCAM US-144MKII audio interface.
 */
extern const struct snd_pcm_hardware tascam_pcm_hw;

/**
 * tascam_playback_ops - ALSA PCM operations for playback.
 *
 * This structure defines the callback functions for playback stream operations.
 */
extern const struct snd_pcm_ops tascam_playback_ops;

/**
 * tascam_capture_ops - ALSA PCM operations for capture.
 *
 * This structure defines the callback functions for capture stream operations.
 */
extern const struct snd_pcm_ops tascam_capture_ops;

/**
 * playback_urb_complete() - Completion handler for playback isochronous URBs.
 * @urb: the completed URB
 *
 * This function runs in interrupt context. It calculates the number of bytes
 * to send in the next set of packets based on the feedback-driven clock,
 * copies the audio data from the ALSA ring buffer, and resubmits the URB.
 */
void playback_urb_complete(struct urb *urb);

/**
 * feedback_urb_complete() - Completion handler for feedback isochronous URBs.
 * @urb: the completed URB
 *
 * This is the master clock for the driver. It runs in interrupt context.
 * It reads the feedback value from the device, which indicates how many
 * samples the device has consumed. This information is used to adjust the
 * playback rate and to advance the capture stream pointer, keeping both
 * streams in sync. It then calls snd_pcm_period_elapsed if necessary and
 * resubmits itself.
 */
void feedback_urb_complete(struct urb *urb);

/**
 * capture_urb_complete() - Completion handler for capture bulk URBs.
 * @urb: the completed URB
 *
 * This function runs in interrupt context. It copies the received raw data
 * into an intermediate ring buffer and then schedules the workqueue to process
 * it. It then resubmits the URB to receive more data.
 */
void capture_urb_complete(struct urb *urb);

/**
 * tascam_stop_pcm_work_handler() - Work handler to stop PCM streams.
 * @work: Pointer to the work_struct.
 *
 * This function is scheduled to stop PCM streams (playback and capture)
 * from a workqueue context, avoiding blocking operations in interrupt context.
 */
void tascam_stop_pcm_work_handler(struct work_struct *work);

/**
 * tascam_init_pcm() - Initializes the ALSA PCM device.
 * @pcm: Pointer to the ALSA PCM device to initialize.
 *
 * This function sets up the PCM operations, adds ALSA controls for routing
 * and sample rate, and preallocates pages for the PCM buffer.
 *
 * Return: 0 on success, or a negative error code on failure.
 */
int tascam_init_pcm(struct snd_pcm *pcm);

/**
 * us144mkii_configure_device_for_rate() - Set sample rate via USB control msgs
 * @tascam: the tascam_card instance
 * @rate: the target sample rate (e.g., 44100, 96000)
 *
 * This function sends a sequence of vendor-specific and UAC control messages
 * to configure the device hardware for the specified sample rate.
 *

Annotation

Implementation Notes