mapping from one mdl to another with extra data
in [Device Drivers]
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From: mudehuai on 8 Nov 2009 11:59 Hi: I am new to driver and want to modify the bulkusb example to talk to our device. The problem is that when the driver receives the raw data from the user space, I need to add a header to it before sending the data to the device. In BulkUsb_DispatchReadWrite(), it calls the IoBuildPartialMdl to map the user mdl directly to the URB mdl allocated by the driver. In my case, i want the new URB mdl to include a header and then the data described by the user mdl. I cannot figure out how to do this with MDL manipulation. I thought about allocate a buffer in the driver and fill it with the header and the data described by the user mdl. Then create the new URB mdl from this buffer. However, it would be great if I can avoid this extra copy with MDL manipulation. Thanks in advance. cheers,
From: eagersh on 9 Nov 2009 18:23 On Nov 8, 9:59 am, mudehuai <mudeh...(a)discussions.microsoft.com> wrote: > Hi: > > I am new to driver and want to modify the bulkusb example to talk to our > device. > > The problem is that when the driver receives the raw data from the user > space, I need to add a header to it before sending the data to the device.. > > In BulkUsb_DispatchReadWrite(), it calls the IoBuildPartialMdl to map the > user mdl directly to the URB mdl allocated by the driver. In my case, i want > the new URB mdl to include a header and then the data described by the user > mdl. > > I cannot figure out how to do this with MDL manipulation. > > I thought about allocate a buffer in the driver and fill it with the header > and the data described by the user mdl. Then create the new URB mdl from this > buffer. > > However, it would be great if I can avoid this extra copy with MDL > manipulation. > > Thanks in advance. > > cheers, The easiest way is to allocate buffer with extra space in user application program. In this case you don't need to manipulate with MDL. It is hard in your case to merge two Mdl's. Igor Sharovar
From: Tim Roberts on 10 Nov 2009 01:30 mudehuai <mudehuai(a)discussions.microsoft.com> wrote: > >I am new to driver and want to modify the bulkusb example to talk to our >device. > >The problem is that when the driver receives the raw data from the user >space, I need to add a header to it before sending the data to the device. > >In BulkUsb_DispatchReadWrite(), it calls the IoBuildPartialMdl to map the >user mdl directly to the URB mdl allocated by the driver. In my case, i want >the new URB mdl to include a header and then the data described by the user >mdl. Does it have to be part of the same transfer? Can you create a new URB with just the header, and then forward the original URB unchanged? >I cannot figure out how to do this with MDL manipulation. You can't do it with MDL manipulation. >I thought about allocate a buffer in the driver and fill it with the header >and the data described by the user mdl. Then create the new URB mdl from this >buffer. > >However, it would be great if I can avoid this extra copy with MDL >manipulation. Nope. If you can't send it as two transfers, then you'll need to copy. -- Tim Roberts, timr(a)probo.com Providenza & Boekelheide, Inc.
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