Re: [PATCH 2.6-git] SPI core refresh

[Vitaly Wool]

Stephen Street wrote:

> On Wed, 2005-11-30 at 13:36 -0800, David Brownell wrote:
>  
>
> > > - it is DMA-safe
> > >      
> > Which as I pointed out is incorrect.  The core API (async) has always
> > been fully DMA-safe.  And a **LOT** lower overhead than yours, which
> > allocates buffers behind the back of drivers, and encourages lots of
> > memcpy rather than just doing DMA directly to/from the buffers that
> > are provided by the SPI protocol drivers.
> >    
>
> Minimal (or no) core intervention on the DMA code path is a good thing.
> I need to fix some broken hardware with software and must to move 96
> bytes from one SPI device to another on the same SPI bus every for 4ms.
> Needless memcpy's will cause substantial performance problems in my
> application. Thinner is definitely better.
>  
Oh yep, I must agree with you here, thanks.
However, it's not a big thing to change memcpy to spi_memcpy which will 
copy the data only when necessary.
That's what I definitely had been doing but didn't include in the patch 
sent, oops. :(
I'll come up with that shortly.

Vitaly
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/