Microsoft KB Archive/134908

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SCSI Miniport Data Transfer Restrictions for IDE Controllers

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Q134908

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The information in this article applies to:


 * Microsoft Win32 Device Driver Kit (DDK) for Windows NT, version 3.51

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SUMMARY
The current implementation for SCSI miniports does not allow an IDE controller to transfer both PIO and busmaster DMA intermixed on a single channel. The miniport must either do PIO or busmaster DMA on a channel, not a mix of the two transfer methods. Note that one channel may be set up to do only PIO transfers, while a second channel may be set up to do only busmaster DMA.

MORE INFORMATION
During the HwScsiFindAdapter routine, the miniport should determine the devices connected to the channel. If there is one PIO device and one DMA device connected, the miniport must only do PIO transfers and change the PORT_CONFIGURATION_STRUCTURE so Master is TRUE and NeedPhysicalAddresses is FALSE.

If both devices on the channel are the same, the miniport must adjust the PORT_CONFIGURATION_STRUCTURE to indicate only PIO or busmaster DMA by setting appropriate values in MapBuffers, Master, and NeedPhysicalAddresses.

This limitation may be removed in a future release of Windows NT. At this time, there are no plans to handle these types of transfers. If there is a change, information will be added to this article.

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Technology : kbAudDeveloper kbWinDDKSearch kbWin32sSearch kbWin32DDKSearch kbWin32DDKNT351 kbWin32DDKNTSearch