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From: "Søren Gullach" <sgullach@ramtex.dk>
Newsgroups: comp.os.ms-windows.programmer.nt.kernel-mode
Subject: Re: how do you do fast i/o
Date: Mon, 8 Dec 1997 12:52:57 +0100
Lines: 106
Message-ID: <66gn69$eaq$1@mail-in1.inet.tele.dk>
References: <01bcfe5b$671d8c40$3c66ec84@cu-dialup.cornell.edu> <661j3s$mcq$1@mail-in1.inet.tele.dk>
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 Sorry its not Art Baker Its Windows NT Programming in Practice ISBN:
0-87930-472-3

SHG wrote in article <661j3s$mcq$1@mail-in1.inet.tele.dk>...

> Hi
>I have used this code from Art Baker
>
>#ifdef DIRECT_IO
> /* These are the two undocumented calls that we will use to give the
>calling
>  * process I/O access. Ke386IoSetAccessMap() copies the passed map to the
>TSS.
>  *  Ke386IoSetAccessProcess() adjusts the IOPM offset pointer so that the
>newly
>  * copied map is actually used.  Otherwise, the IOPM offset points beyond
>the
>  * end of the TSS segment limit, causing any I/O access by the user-mode
>  * process to generate an exception. */
> extern "C" void Ke386SetIoAccessMap(int, IOPM *); // 1 copy buffer, 0 fill
>with 0xFF
> extern "C" void Ke386QueryIoAccessMap(int, IOPM *); // 1 copy buffer, 0
>fill with 0xFF
> extern "C" void Ke386IoSetAccessProcess(PEPROCESS, int); // 1 enable IO, 0
>disable IO
>#endif
>
>This code is in the DispatchOpen
>#ifdef DIRECT_IO
> // Alter NT IO map so app on ring 3 can do IO
> if( pDeviceExtension->fDirectIO != 0 )
> {
>  IOPM *pIOPM; // pointer to IO protection map
>
>  pIOPM = (IOPM*)MmAllocateNonCachedMemory(sizeof(IOPM));
>  if(pIOPM == NULL)
>  {
>   hwioRegDebug( L"DispatchCreate", (USHORT)0xFF, L"Direct IO NOT set" );
>   Status = STATUS_INSUFFICIENT_RESOURCES;
>  }
>  else
>  {
>   hwioRegDebug( L"DispatchCreate",
>(USHORT)pDeviceExtension->NtDeviceNumber, L"Direct IO set" );
>   Ke386QueryIoAccessMap(1, pIOPM); // 1 copy buffer, 0 fill with 0xFF
>
>   // Alter IO bits
>   USHORT PortFirst = (USHORT)(pDeviceExtension->IntelPortBase);
>   USHORT PortLast =
>(USHORT)(pDeviceExtension->IntelPortBase+pDeviceExtension->PortCount);
>//hwioRegDebug( L"DispatchCreate port first",
>(USHORT)pDeviceExtension->NtDeviceNumber, (ULONG)PortFirst );
>//hwioRegDebug( L"DispatchCreate port last",
>(USHORT)pDeviceExtension->NtDeviceNumber, (ULONG)PortLast );
>   for( USHORT p=PortFirst; p<PortLast; p++ )
>   {
>    (*(pIOPM))[p/8] &= (UCHAR)(0xFF7F>>(p%8));
>   }
>
>   Ke386IoSetAccessProcess(PsGetCurrentProcess(), 1); // 1 enable IO, 0
>disable IO
>   Ke386SetIoAccessMap(1, pIOPM ); // 1 copy buffer, 0 fill with 0xFF
>
>   MmFreeNonCachedMemory( pIOPM, sizeof(IOPM) );
>  }
> }
> else
>  hwioRegDebug( L"DispatchCreate",
(USHORT)pDeviceExtension->NtDeviceNumber,
>L"Direct IO disabled" );
>#endif
>
>This code is in DispatchClose
>#ifdef DIRECT_IO
> PDEVICE_EXTENSION pDeviceExtension =
>(PDEVICE_EXTENSION)pDeviceObject->DeviceExtension;
>
> if( pDeviceExtension->fDirectIO != 0 )
> {
>  hwioRegDebug( L"DispatchClose", (USHORT)pDeviceExtension->NtDeviceNumber,
>L"Direct IO removed" );
>  Ke386IoSetAccessProcess(PsGetCurrentProcess(), 0); // 1 enable IO, 0
>disable IO
> }
>#endif
>
>Søren Gullach
>SGullach@ramtex.dk
>
>
>John Landau wrote in article
><01bcfe5b$671d8c40$3c66ec84@cu-dialup.cornell.edu>...
>
>>Hi,
>>     I think it was Art Baker in his The Windows NT Device Driver Book
>>who said that for highest performance I/O you'd make the I/O page
>>accessible to user-mode code.
>>    How is this done? Are there any books on NT Device Drivers that
>>address this and/or other optimization issues?
>>     Regards,
>>     John
>>
>
>