Open Sound System
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Driver for the ACME Laboratories Evil Audio family of sound cards


This description section contains general information about the driver and the name and contact information of author and maintainer of the code.

_NO_ copyright statement must be given in the comments since all drivers to be included in the OSS source tree must be compatible with the copying policy of the rest of OSS.

Create a #define for the copying conditions. This define must be as above. Only the name of the copyright owner and the year(s) can be changed. This definition will be replaced by the actual OSS copyright statement by the build tools.

This file is part of Open Sound System.

Copyright (C) 4Front Technologies 1996-2008.

This this source file is released under GPL v2 license (no other versions). See the COPYING file included in the main directory of this source distribution for the license terms and conditions.

The _cfg.h file for the driver must be included before anything else by all OS drivers. This configuration file will be automatically generated based on the configuration files and operating system requirements.

#include "myossdev_cfg.h"

If the driver is split to multiple C source files then you should create a common header file for the driver and include it here.

#include "myossdev.h"

Drivers for PCI devices need to include <oss_pci.h>. Other drivers should not include it.

#include <oss_pci.h>

The attach routine for the device. This routine will be called once for each device instance found from the system. The osdev parameter is a handle to the device that will be needed by many subsequent OSS core functions.

myossdev_attach (oss_device_t * osdev)
  myossdev_devc_t *devc;

Some debugging printout. All OSS drivers must use cmn_err() instead of printf(), printk() or something else to print debugging and error messages.

The cmn_err() call can be oput inside a DDB() macro. In this way the message will only be printed if OSS was started with detect_trace=1 configuration option.

  DDB (cmn_err (CE_CONT, "myossdev_attach called\n"));

First create the devc structure and initialize it to zeroes. The PMALLOC macro will allocate memory that will be automatically released when OSS gets unloaded. This kind of memory should be used for structures that will stay in use until the driver is unloaded.

  if ((devc = PMALLOC (osdev, sizeof (*devc))) == NULL)
      cmn_err (CE_WARN, "Cannot allocate devc\n");
      return 0;			/* Failure */

  memset (devc, 0, sizeof (*devc));

Drivers must initialize osdev to have a link to the devc structure. Without this link the driver cannot be unloaded.

  osdev->devc = devc;

Init the devc fields and create the mutex. Register the device.

  devc->osdev = osdev;
  MUTEX_INIT (devc->osdev, devc->mutex);
  oss_register_device (osdev, "ACME Labs Evil Audio");

This is all for now. More will follow in the next episode.

  return 1;			/* Success */

Device detach routine. Note that this routine will be called once for each instance.

myossdev_detach (oss_device_t * osdev)
  myossdev_devc_t *devc = osdev->devc;
  int err;

  DDB (cmn_err (CE_CONT, "myossdev_detach called\n"));

Check if the device is not busy.

  if ((err = oss_disable_device (osdev)) < 0)
      cmn_err (CE_WARN, "Cannot detach %s\n", osdev->nick);
      return 0;

Uninitialize the instance variables. Do not try to free any memory allocated with PMALLOC().

  MUTEX_CLEANUP (devc->mutex);	/* Mutexes must be cleared */

Finally mark the device as inactive

  oss_unregister_device (osdev);

  return 1;			/* Ok */

Copyright (C) 4Front Technologies, 2007. All rights reserved.

Back to index OSS web site

Copyright (C) 4Front Technologies, 2007. All rights reserved.
Back to index OSS web site