[gPXE-devel] [PATCH] [jme] Adding JMicron Ethernet driver

[Geoff Lywood]

> -----Original Message-----
> From: gpxe-devel-bounces at etherboot.org [mailto:gpxe-devel-
> bounces at etherboot.org] On Behalf Of Guo-Fu Tseng
> Sent: Saturday, May 29, 2010 1:35 AM
> To: Michael Brown; gpxe-devel at etherboot.org
> Subject: Re: [gPXE-devel] [PATCH] [jme] Adding JMicron Ethernet driver
> 
> On Sat, 29 May 2010 01:04:52 +0100, Michael Brown wrote
> > On Friday 28 May 2010 18:27:00 cooldavid at cooldavid.org wrote:
> > > A new driver for JMicron Ethernet controller.
> >
> > Looks pretty nice!  :)
> >
> > A few comments, based on a very quick look:
> >
> > > +#if __x86_64__
> > > +	rxdesc->desc1.flags	= RXFLAG_64BIT;
> > > +#endif
> >
> > What does this flag actually do?  It's implausible that the card cares
> > which CPU is running on the host system.
> Ahh... Forget to remove it.
> It was intended for preventing gPXE provide over 4G DMA
> address on x86_64 arch. Since the gPXE won't provide any
> address above 4G, this FLAG is not needed.

Currently, it is possible to have a DMA buffer located above 4GB when the system is 64-bit EFI. (However, it seems that other drivers don't deal with this situation correctly, and it might be easier to modify malloc_dma to impose this limit across all build types.)