[PATCH 0/3] patches to allow DTB to be appended to the ARM zImage

[arnd@arndb.de (Arnd Bergmann)]

On Tuesday 14 June 2011 19:28:49 Nicolas Pitre wrote:
> On Tue, 14 Jun 2011, Tony Lindgren wrote:
> 
> > * Nicolas Pitre <nicolas.pitre@linaro.org> [110614 00:04]:
> > > +
> > > +   for_each_tag(atag, atag_list) {
> > > +           if (atag->hdr.tag == ATAG_CMDLINE) {
> > > +                   setprop_string(dt, "/chosen", "bootargs",
> > > +                                     atag->u.cmdline.cmdline);
> > > +           } else if (atag->hdr.tag == ATAG_MEM) {
> > > +                   uint32_t mem_reg_property[2];
> > > +                   mem_reg_property[0] = cpu_to_fdt32(atag->u.mem.start);
> > > +                   mem_reg_property[1] = cpu_to_fdt32(atag->u.mem.size);
> > > +                   setprop(dt, "/memory", "reg", mem_reg_property,
> > > +                              sizeof(mem_reg_property));
> > > +           } else if (atag->hdr.tag == ATAG_INITRD2) {
> > > +                   uint32_t initrd_start, initrd_size;
> > > +                   initrd_start = atag->u.initrd.start;
> > > +                   initrd_size = atag->u.initrd.size;
> > > +                   setprop_cell(dt, "/chosen", "linux,initrd-start",
> > > +                                   initrd_start);
> > > +                   setprop_cell(dt, "/chosen", "linux,initrd-end",
> > > +                                   initrd_start + initrd_size);
> > > +           }
> > > +   }
> > 
> > I think Russell posted a complete list of the ATAGs to translate
> > somewhere, but at least ATAG_REVISION is missing here. That's being
> > used quite a bit as system_rev to set things dynamically.
> 
> No problem.  This is a work in progress.  We still can test the concept 
> and fine tune the actual set of ATAGs being translated.

Let's talk about the revision field now, because it doesn't have a
direct correspondence in existing attributes.

Functionality-wise, this would probably be the "compatible" property
of the root node, with its most specific name to match, but that's not
trivial to generate.

In some cases, the system revisions have significant differences in their
devices (why else would you care about the revision), which means that you
actually need a different device tree per revision anyway. If that's the
common case, we could just ignore it completely or instead have a way
to choose a specific device tree from a list based on the revision.

Another option would be to merge both the ATAG_REVISION and ATAG_SERIAL
into a string and put them into the root "serial-number" property that
is fairly easy to do, but would be harder to parse if you actually rely
on specific values.

	Arnd