Evaluating Your Card

The process of evaluating will help you estimate the amount of effort required to produce a QNX driver:

• Is your card on the PCI bus?

  If yes, the effort required is reduced because the PCI is a well standardized bus, and the card probably has on-chip DMA. Use the standard template driver as your starting point.

  If your card is on the ISA bus, the effort required is increased because you may need to worry about ISA PnP issues or other configuration issues to find and access your chip. Additionally, the chip probably requires the CPU DMA controller to transfer data. Use the Sound Blaster (sb) driver as your starting point.

  If your card is neither PCI or ISA, there's no specific template targeted at your situation. You'll have to learn from both the PCI template and Sound Blaster driver and adapt the knowledge to your specific situation.

• Does your card use a standard Codec (e.g. AC97 or AK4531)?

  If yes, your work will be easier because the DDK provides DLLs to control these codecs. If your card is PCI-based, use the standard template driver as your starting point. If the card isn't PCI-based, you have to create a hybrid from both templates. For more information, see the Supported Codecs appendix.

  If no, you'll have to write all the mixer control for this codec yourself. Use the Sound Blaster driver as your starting point. If the card is PCI-based, you'll have to create a hybrid from both templates.

• Does your card support playback of only one stream?

  Handling a multistream or subchannel card requires a little more effort and planning but provides the most economical driver. If your card has only one stream, the architecture provides a PCM software mixing interface where multiple streams are mixed down to just one stream that's directed to your driver.

• Will you support your card on both little and big endian machines?

  If you intend to support your chip on platforms with both types of endianness, be advised that this will impact CPU performance (on the nonnative machine) because data has to be converted whenever you read or write a register.

• Which PCM data formats will you card accept?
• What PCM rates will the card support?