[ros-dev] Re: [ros-svn] [hbirr] 17665: - Copy the map registers to the buffer only, if they are used (in IoFlushAdapterBuffers).

Filip Navara xnavara at volny.cz
Tue Sep 6 00:50:00 CEST 2005

Hartmut Birr wrote:

>Filip Navara wrote:
>>- At first, the UseMapRegisters variable you added to
>>MAP_REGISTER_ENTRY structure isn't needed. IoFlushAdapterBuffers can
>>determine the information itself and the case was clearly marked as
>This case isn't marked as UNIMPLEMENTED and FIXME. The using of hardware
>scatter/gather is marked as UNIMPLEMENTED and FIXME. I've modified the
>cache manager a little bit. The cache segments for the floppy driver
>allocated from below the 16MB limit. I get no data from a floppy.
The UNIMPLEMENTED case is entered for any adapter that claims that it 
can support hardware scatter/gather regardless of it being used or not. 
A quick untested patch is attached (I'm not sure it will work, since it 
looks like I forgot to initialize MapRegisterBase->Counter...). I'm 
planning to look at it.

>>- The byte offset is added for a reason. I know the stuff that it is
>>supposed to solve is broken atm, but the rationale is that there can
>>be more IoMapTransfer calls and together with
>>MAP_REGISTER_ENTRY->Counter you can setup more transfers... It's
>>explained in
>It makes no sense to call IoMapTransfer more than ones without a call to
>IoFlushAdapterBuffers for the pc dma controllers. For the pc dma
>controllers, a transfer has to be finished, before the next can be
It applies to non-system-DMA... Quoting NT4 DDK documentation: "The 
driver of a busmaster device with scatter/gather support can use the 
returned logical address and updated Length value to build a 
scatter/gather list, calling IoMapTransfer repeatedly until it has used 
all available map registers for the transfer operation."

>It is always possible to call IoFlushAdapterBuffers after each
>transfer and before the next is started. The reference doesn't explain
>something about to setup more transfers.
See above.

I'll try to write more tomorrow, but my mind is getting foggy now...

Best regards,
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