Full Code Example

Example 2-1. Basic Flow for PCI Drivers Example

  #include <sound/driver.h>
  #include <linux/init.h>
  #include <linux/pci.h>
  #include <linux/slab.h>
  #include <sound/core.h>
  #include <sound/initval.h>

  /* module parameters (see "Module Parameters") */
  static int index[SNDRV_CARDS] = SNDRV_DEFAULT_IDX;
  static char *id[SNDRV_CARDS] = SNDRV_DEFAULT_STR;
  static int enable[SNDRV_CARDS] = SNDRV_DEFAULT_ENABLE_PNP;

  /* definition of the chip-specific record */
  struct mychip {
          struct snd_card *card;
          // rest of implementation will be in the section
          // "PCI Resource Managements"
  };

  /* chip-specific destructor
   * (see "PCI Resource Managements")
   */
  static int snd_mychip_free(struct mychip *chip)
  {
          .... // will be implemented later...
  }

  /* component-destructor
   * (see "Management of Cards and Components")
   */
  static int snd_mychip_dev_free(struct snd_device *device)
  {
          return snd_mychip_free(device->device_data);
  }

  /* chip-specific constructor
   * (see "Management of Cards and Components")
   */
  static int __devinit snd_mychip_create(struct snd_card *card,
                                         struct pci_dev *pci,
                                         struct mychip **rchip)
  {
          struct mychip *chip;
          int err;
          static struct snd_device_ops ops = {
                 .dev_free = snd_mychip_dev_free,
          };

          *rchip = NULL;

          // check PCI availability here
          // (see "PCI Resource Managements")
          ....

          /* allocate a chip-specific data with zero filled */
          chip = kzalloc(sizeof(*chip), GFP_KERNEL);
          if (chip == NULL)
                  return -ENOMEM;

          chip->card = card;

          // rest of initialization here; will be implemented
          // later, see "PCI Resource Managements"
          ....

          if ((err = snd_device_new(card, SNDRV_DEV_LOWLEVEL,
                                    chip, &ops)) < 0) {
                  snd_mychip_free(chip);
                  return err;
          }

          snd_card_set_dev(card, &pci->dev);

          *rchip = chip;
          return 0;
  }

  /* constructor -- see "Constructor" sub-section */
  static int __devinit snd_mychip_probe(struct pci_dev *pci,
                               const struct pci_device_id *pci_id)
  {
          static int dev;
          struct snd_card *card;
          struct mychip *chip;
          int err;

          /* (1) */
          if (dev >= SNDRV_CARDS)
                  return -ENODEV;
          if (!enable[dev]) {
                  dev++;
                  return -ENOENT;
          }

          /* (2) */
          card = snd_card_new(index[dev], id[dev], THIS_MODULE, 0);
          if (card == NULL)
                  return -ENOMEM;

          /* (3) */
          if ((err = snd_mychip_create(card, pci, &chip)) < 0) {
                  snd_card_free(card);
                  return err;
          }

          /* (4) */
          strcpy(card->driver, "My Chip");
          strcpy(card->shortname, "My Own Chip 123");
          sprintf(card->longname, "%s at 0x%lx irq %i",
                  card->shortname, chip->ioport, chip->irq);

          /* (5) */
          .... // implemented later

          /* (6) */
          if ((err = snd_card_register(card)) < 0) {
                  snd_card_free(card);
                  return err;
          }

          /* (7) */
          pci_set_drvdata(pci, card);
          dev++;
          return 0;
  }

  /* destructor -- see "Destructor" sub-section */
  static void __devexit snd_mychip_remove(struct pci_dev *pci)
  {
          snd_card_free(pci_get_drvdata(pci));
          pci_set_drvdata(pci, NULL);
  }