Returns the maximum size of the buffer that may be used with the PsRequestWriteMmioLinear function.
PPS_REQUEST pRequest
An opaque handle to a request created by the PsRequestCreate function.
If the function succeeds, it returns a non-zero value for the size of the buffer in bytes.
If it fails, it returns 0 (zero) due to one of the following possible reasons:
The maximum buffer size is subject to change depending on the debug protocol version.
The effective buffer size may be smaller depending on the MMIO access size. For example, if the access size is 4 and the maximum size is 0x123, the effective maximum size would be 0x120 because the buffer should be aligned for 4-byte access.