x86_64_defconfig and i386_defconfig: What is the difference?

[Rajat Jain]

Hi,

> -----Original Message-----
> From: Valdis.Kletnieks at vt.edu [mailto:Valdis.Kletnieks at vt.edu]
> Sent: Tuesday, September 09, 2014 7:28 AM
> To: Matthias Brugger
> Cc: Rajat Jain; linux-newbie at vger.kernel.org; kernelnewbies
> Subject: Re: x86_64_defconfig and i386_defconfig: What is the difference?
> 
> On Tue, 09 Sep 2014 16:06:07 +0200, Matthias Brugger said:
> 
> > > Can someone tell me if the i386 one is to be used when we want to
> > > build for a 32bit machine and the x86_64 is to be used for 64 bit machine?
> >
> > You can build the kernel with any architecture for any architecture.
> > This is called cross-compiling. The homepage [0] should explain you
> > how to do that.
> 
> Right, but you still need to use a .config appropriate for the target machine,
> which is what I think Rajat was asking about.

Right.

I'm trying to generate x86 images for someone else to test, who's going to test it on a standard / generic x86 machine:

https://lkml.org/lkml/2014/9/9/35

What I was not sure is that which config should I use to generate an image for a "standard x86 machine". Now I do understand (I provided him 2 images - 1 for the 32 bit (using i386_defconfig) and another for 64 bit (using x86_64_defconfig).

Thanks,

Rajat


> 
> A defconfig is usually only known verified to boot on a few (possibly one)
> examples of that architecture hardware.  For embedded ARM, it may be one
> specific development board or hardware device.  For x86, I think they try to
> keep it "will probably kind of sort of boot on generic PC hardware with a
> common distro, but anything fancylike a webcam or better graphics than "vga
> tty emulation" may not work".
> 
> A defconfig is pretty much just a proof of concept starting point for an actual
> working config for a given hardware system.