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

[Filip Navara]

Filip Navara wrote:

>   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
> > >  UNIMPLEMENTED and FIXME.
> > >     
> >  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
> > >  http://download.microsoft.com/download/e/b/a/eba1050f-a31d-436b-9281-92cdfe…
> > >
> > >
> > >     
> >  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
> >  started.
> >  
>  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... 
Oh, this time with the right patch...

- Filip