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This sample driver is a template for a PCI busmaster DMA device that
generates interrupts. Included is a small Win32 console mode application
that sends I/O requests to the driver.
The code assumes a single I/O per interrupt. If more than one I/O per
interrupt is to be supported, the driver must be modified. Also, when the
interrupt fires, the driver checks for a current I/O. If there is not a
current I/O, the ISR only clears the interrupt. If you want a DPC to run
even if there is no current I/O, you will have to change the driver design.
Important Note
This sample driver implements specific PCI SCSI registers, for a specific
PCI vendor. Before using this driver, insure that the vendor-specific
portions of the code have been removed or modified. Failure to take
these precautions could cause a working system to fail unexpectedly.
All the vendor unique code should have been identified with a VENDOR_UNIQUE
comment. If you are using this code, you are responsible for insuring that
the code does not cause undesired side-effects.
The PciDma.sys driver is not a replacement SCSI driver.
The sample driver cannot run at the same time as the Symbios Logic SCSI
driver -- only one or the other driver will run. If the SCSI driver is
used to control the boot device, the PciDma.sys driver should not be
used or the system may become unbootable. Do not disable the SCSI
driver unless you are sure it is not needed to boot.
Build Instructions
To run the sample:
- Build the driver and Win32 test application. See the DDK documentation
for details on creating drivers and Win32 applications from the DDK
Build Environment.
- Copy the driver to the test computer. PciDma.sys goes into
%systemroot%\system32\drivers directory on the test computer.
- Add the driver to the test computer's registry. Using Windows Explorer,
right-click the PciDma.reg file and select Merge. Restart your computer
to update the cached registry information.
- Restart your computer.
- Start the driver. After restarting your computer, you can start the
driver from the Command Prompt window by typing "net start pcidma". The
driver can also be started by going to the Control Panel, opening
Devices, highlighting the PciDma driver in the Devices dialog box, and
clicking Start.
- Run the test program. The test program requires parameters to
run. From the Command Prompt window, run the test program without
parameters to see the required switches.
Symbios Logic 53c815 Implementation Details
This section provides information about how this driver controls the
Symbios Logic PCI SCSI device.
For simplicity, the driver sets up a hardware timer on the Symbios 53c815.
When the hardware timer fires, the PCI device interrupts the CPU. The
driver ISR runs, queues the DPC, and the DPC completes a single pending
I/O. This driver was created to support only one I/O per interrupt.
This sample driver doesn't actually DMA data to the user buffer. However,
the code to prepare the buffers for DMA transfer has been extracted from
several working drivers.
The specific registers that are used to control functionality are
documented in the hardware specifications available from Symbios Logic.