On 06/14/2011 06:50 PM, Nicolas Pitre wrote:

On Tue, 14 Jun 2011, Rob Herring wrote:

quoted

On 06/14/2011 03:32 PM, Arnd Bergmann wrote:

quoted

On Tuesday 14 June 2011 19:28:49 Nicolas Pitre wrote:

quoted

On Tue, 14 Jun 2011, Tony Lindgren wrote:

quoted

* Nicolas Pitre [off-list ref] [110614 00:04]:

quoted

+
+   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.

IIRC, system_rev at least can be specified on the kernel command line,
so you could just append the cmd line. However, if you force the
built-in command line to be used that would not work,

If you do that then you probably don't care as much about translating 
existing ATAGs from the bootloader and could as well just live with the 
hardcoded values in the appended DTB.

What I meant was you could translate these ATAGs into the DTB kernel
command-line options rather than come-up with something new. You already
having to mess with the command line.

Rob