jkh weird problem (reading pci device memory)

[John-Mark Gurney]

John Baldwin wrote this message on Tue, Aug 08, 2006 at 13:42 -0400:
> On Monday 07 August 2006 18:05, John-Mark Gurney wrote:
> > John Baldwin wrote this message on Mon, Aug 07, 2006 at 15:27 -0400:
> > > 	sc->cfg_table.signature = letoh32(bus_read_4(sc->bar.res, 0));
> > > 	sc->cfg_table.version = letoh16(bus_read_2(sc->bar.res, 4));
> > > 	sc->cfg_table.dummy = bus_read_1(sc->bar.res, 5);
> > 
> > Note that this may or may not be correct...  the bus_read_X macros
> > do endian conversion if the bus is of different endianness than the
> > processor arch...  So if the device is on a PCI bus, and the machine
> > is sparc64, the bus_read_X will already be swapped as necessary... If
> > you don't want the byte swapping to be done for you, there are the
> > _stream versions...  The are useful for transfering data like disk
> > data that needs to maintain the same order...
> 
> Then why are folks adding these macros to things like mpt?

I haven't seen the patches for mpt, but usually they are only doing
the byte swapping to data structures that are to be dma'd to/from
the card...  As when dma happens, there is no byte swapping done..

-- 
  John-Mark Gurney				Voice: +1 415 225 5579

     "All that I will do, has been done, All that I have, has not."