[U-Boot] [PATCH 5/5] Warn when the machine ID isn't passed to an ARM kernel and u-boot is compiled in debug mode. The kernel cannot boot without it.

[Jason]

On Mon, Jul 04, 2011 at 02:55:54PM -0400, Christopher Harvey wrote:
> On Mon, Jul 04, 2011 at 02:08:44PM -0400, Jason wrote:
> > On Mon, Jul 04, 2011 at 01:45:41PM -0400, Christopher Harvey wrote:
> > > +	   Hopefully there will never be this many machines. 
> > > +	   Can't use 0 since 0 is already used as a mach-type. */
> > > +	gd->bd->bi_arch_number = 0xffffffff; 
> > >  
> > >  	gd->bd->bi_baudrate = gd->baudrate;
> > >  	/* Ram ist board specific, so move it to board code ... */
> > > diff --git a/arch/arm/lib/bootm.c b/arch/arm/lib/bootm.c
> > > index 802e833..70b3b76 100644
> > > --- a/arch/arm/lib/bootm.c
> > > +++ b/arch/arm/lib/bootm.c
> > > @@ -113,6 +113,12 @@ int do_bootm_linux(int flag, int argc, char *argv[], bootm_headers_t *images)
> > >  		printf ("Using machid 0x%x from environment\n", machid);
> > >  	}
> > >  
> > > +#ifdef DEBUG
> > > +	if(machid==0xffffffff) {
> > > +	        debug("\nWarning: machid not set! Linux will not finish booting.\n\n");
> > 
> > s/finish/start/ ;-)
> >
> I'll have to disagree here.  Linux will decompress and some functions
> will run but it will eventually stop, hence will not finish.

On further investigation, you're right, it doesn't finish
starting/booting.  Sorry for the noise.

> > Also, shouldn't the compile fail in this case (#error)?  Or, at least #warn?
> >
> The compiler can't know what machid will be at runtime. Maybe a "would
> you like to continue?" prompt could work.

Since the kernel throws a nice fat error message when the MACH_TYPE
doesn't match what it was compiled for, I don't see the point to adding
another message at the same point in the development process.

Perhaps use the constant CONFIG_MACH_TYPE, set to 0xffffffff.  Each
board config file sets it to MACH_TYPE_WHATEVER and then you could
do:

#if CONFIG_MACH_TYPE == 0xffffffff
#warning "Machine type not set!  Linux will not finish booting!"
#endif

You could use -Werror to fail on such things.  DBGFLAGS in ./config.mk
might be a good place.

If the maintainers choose to move to a menuconfig style configuration
system, this logic could be handled in there (invalid config file).
 
> > Please take comments with a grain of salt, I'm asking, not telling.  I'm
> > fairly new to this as well.
> >
> I'm happy to clarify. 

Thanks for exercising my brain before I seek out the beer and
explosives. ;-)

Jason.