patches to allow DTB to be appended to the ARM zImage

Quoted 53 lines · Rob Herring

Quoted 51 lines · Arnd Bergmann

Quoted 25 lines · On Tuesday 14 June 2011 19:28:49 Nicolas Pitre wrote:

Quoted 23 lines · Tony Lindgren

Quoted 21 lines · Nicolas Pitre

(quoted diff) +21 -0

+
+   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);
+           }
+   }

Quoted 6 lines

Quoted 3 lines

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.

Quoted 3 lines

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.