How to Write an ATAport Miniport

1. How to Write an ATAport Miniport

2. Outline • Current ATA Environment • ATAport Solution • ATAport Features • ATAport Model • Best Known Practices

3. Industry Activities • Many Vendor ATA drivers areScsiport miniports • Creating an inconsistent behavior around ATA command handling • Emphasis on consumer RAID • The introduction of SATA interconnect • Requires new feature support • Has a richer host controller interface • Still uses ATA, which is a duplicate of a significant portion of the ATA driver infrastructure

4. ATAport Goals • Extensibility • Support innovations in the ATA industry • Compatibility • Accommodates existing andnew hardware • Flexibility • Enables Vendor value add • Diagnosability

5. ATAport Features • ATA/ATAPI 7 support • Forced Unit Access • Advanced Power Management • SATA support • Support for greater than 2 channels/controller • Support for greater than 2 devices/channel • Command Queuing • Channel-based queuing • Device-based queuing

6. ATAport Features • Support for Message Signal Interrupts • Provides greater flexibility and stability in interrupts • Hotplug • More granular Power Management control • ATAport provides a flexible miniport interface for vendor value add

7. ATAport Model: Port Services • Translation of upper OS storage requests into ATA protocol • Automatic Generation of Sense Data for ATA devices • Push model as opposed to a Pull model • Improved IDE Request Block that more accurately maps to the underlying hardware model

8. ATAport Model: Port Services • Asynchronous device reset management • Hierarchical reset (device and channel) • Asynchronous device power management • Per-channel granularity • Power, resets, queuing, interrupts • I/O is concurrent

9. ATAport Model: Miniport Capabilities • Negotiation of Device parameters • Transfer mode • Bytes/Sector • Sectors/block • LBA sectors/disk • Removable media • Decide on channel- or device-based command queuing • Control the timeout on a per-request basis • Request the mapping of data buffers on a per request basis • Miniport can participate in the queuing policy • Selection of depth, freezing,retry

10. ATAport Interface Illustration Default Miniport ATAport Channel 1 Channel 0 Disk Channel Interface Disk Controller Interface Port IO Hardware Pciidex Vendor Miniport BAR CS

11. Controller Interface ATAport Miniport Driver Entry AtaPortInitializeEx Start Controller AtaControllerIntitialize AdapterControl w/ IdeStart Enumerate Channels AtaControllerChannelEnabled ControllerChannelEnabled ChannelInitialize

12. Channel Interface ATAport Miniport Initialize Channel ChannelInitialize ChannelInitialize Start Channel AtaChannelControl HwControl w/ IdeStart Configure Devices AtaHwIntitialize HwIntitialize I/O HwBuildIO AtaHwBuildIO AtaHwStartIO HwStartIO AtaHwInterrupt HwInterrupt

13. Trick: Extensions • Keep track of extensions in global variables • Finding Channel Extensions !devstack 0x8245dbf8 !DevObj !DrvObj !DevExt ObjectName 8246a030 \Driver\disk 8246a0e8 disk 8245c478 \Driver\ACPI 8245ac80 0000008a 8245dbf8 \Driver\msahci 8245dcb0 ataport Channel extension is DevExt +0x84 • Finding the Controller Extension !devstack 0x8245dbf8 !DevObj !DrvObj !DevExt ObjectName 8246a030 \Driver\msahci 8246a0e8PciIde2 8245c478 \Driver\ACPI 8245ac80 0000008a 8245dbf8 \Driver\pci 8245dcb0 NTPNP_PCI0012 Controller Extension is DevExt +0x88 • No device objects during crashdump

14. Best Known Practices: CrashDump/Hybernate • Creates an unused copy of the miniport at boot time • Has no driver stack, runs single threaded, processes 1 IO at a time • Can be identified by ChannelConfiguration.ChannelMode • Cannot touch PCI config space • Cannot use more than 30KB of uncached extension per channel

15. Trick: Stalling • AtaPortStallExecution • Spinlocks the CPU for x microseconds • Should not be used for greater than 1 millisecond delays • AtaPortRequestTimer • Causes the port driver to trigger a callback routine after x microseconds • Should be used for greater than 1 millisecond delays • Best when used with multiphase functions • Remember crashdump is single-threaded

16. Best Known Practices: Memory Allocation • Uncached Extension allocation can only be done during Start Channel • AtaPortGetPhysicalAddress retrieves physical address for: • IRB's data buffer • IRB's IrbExtension • Miniport's uncached extension • SGList Entries and Page Breaks

17. Best Known Practices: Queuing • Per Channel • Use IDE_UNTAGGED for TargetID on QueueTag function calls • Per Device • Use TargetID on QueueTag function calls • Always, Always pause the queue with AtaPortDeviceBusy when failing an IRB with IRB_STATUS_BUSY

18. Best Known Practices: Bus Configuration Changes • ChannelEnable is optional and only used to validate the channel • Critical hardware operations should not be done in ChannelEnable • ChannelEnable will only be called during QueryDeviceRelations • Use AtaPortBusChangeDetected to reenumerate a channel • Use AtaPortDeviceArrived and AtaPortDeviceRemoved for device hotplug

19. Best Known Practices: IO Error Reporting • STATUS_BUSY • Host is busy • Make sure to pause the queues with AtaPortDeviceBusy • SELECTION_TIMEOUT • Device busy • Not necessarily retried • IRB AtaStatus and Error fields • Only valid on Selection_Timeout, and Error

20. Summary • ATAport is an improved port-miniport interface for ATA-based controllers • ATAport supports the latest ATA and architecture features

21. Additional Resources • ATA Miniport Interface • Documented in the WDK • List of Specifications • ATA - http://www.t13.org • SATA - http://www.serialata.org • SCSI - http://www.t10.org • AHCI - http://developer.intel.com/technology/serialata/ahci.htm

22. © 2005 Microsoft Corporation. All rights reserved. This presentation is for informational purposes only. Microsoft makes no warranties, express or implied, in this summary.