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  · DriverStudio          Using IOCTL METHOD_IN/OUT_DIRECT
  · DriverBundle
  · Previews              When an application calls the Win32 API
  · Compatibility         DeviceIoControl to access a device driver, it passes
 [Downloads]  ·           a code to specify the operation that it is
                          requesting. The driver writer supplies a set of
 Wizards                  codes, each of which is formed using macro CTL_CODE.
  · Utilities             One parameter to CTL_CODE specifies the buffer access
  · NT source             method that the operation uses. The method may be one
 examples                 of the following:
  · VxD source
 examples                    * METHOD_BUFFERED
  · WDM source               * METHOD_IN_DIRECT
 examples                    * METHOD_OUT_DIRECT
 [Resources]  ·              * METHOD_NEITHER
 Technical papers
  · Useful links          The semantics of METHOD_IN_DIRECT and
  · Technical tips        METHOD_OUT_DIRECT cause some confusion for driver
 [Support]  ·             developers. The buffer pointed to by parameter
                          InputBuffer (unless NULL) is copied to a system
 Support                  buffer, and the system inserts a pointer to the
  · Knowledge base        system buffer in the IRP sent to the driver. For the
  · Problem               buffer to which parameter OutputBuffer points, the
 submission               systems creates an MDL, after probing and locking the
  · Product               corresponding memory pages. The MDL address appears
 registration             in the IRP at field MdlAddress.
  · Release notes
 [Shop NuMega]  ·         The buffer pointed to by parameter InputBuffer never
 Buy it!                  receives any data from the driver. However, note that
  · Price list            the buffer pointed to by parameter OutputBuffer is
  · How to buy            sometimes an input buffer (METHOD_IN_DIRECT) and
  · Sales offices         sometimes an output buffer (METHOD_OUT_DIRECT). In
                          the latter case, the buffer must be writable, or the
                          system will fail the call.
 [Y2K Compliance]
                          Click here to read about METHOD_NEITHER.

 [More information]       Back to technical tip start page.


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