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

[Filip Navara]

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...

Best regards,
Filip