Current-Users archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

Re: BCM5809S support in bnx(4) and brgphy(4)

On Wed, 1 Dec 2010, Izumi Tsutsui wrote:

> >  Also, there is a comment above saying that:
> > 
> >  /*
> >   * The following data structures are generated from RTL code.
> >   * Do not modify any values below this line.
> >   */
> IMO all members fetched via PCI bus master should be uint32_t
> if hardware supports byte swap ops since swap is always done
> against each uint32_t.



> Well, no need to use #if BYTE_ORDER if we use uint32_t with
> shift ops because word swap is done by hardware.
> (that's the reason why we have to swap uint16_t members by #ifdef)

What swap is done by what hardware?  Most of the time any swapping is done 
by a series of shift and mask instructions with the current 
implementation, and swapping a 16-bit value is much less expensive than 
swapping a 32-bit value.

Sigh.  I really need to get off my butt and add a bunch of bus_dma 
accessors (like the bus_space ones but for DMA buffers) to solve this 
problem optimally across all architectures.


Home | Main Index | Thread Index | Old Index