On Thu, 16 Jun 2011, David Gibson wrote: > On Wed, Jun 15, 2011 at 03:50:37PM -0400, Nicolas Pitre wrote: > > On Tue, 14 Jun 2011, David Brown wrote: > > > > > Some targets have multiple memory regions. Parse up to 8 of these > > > when converting the atags to fdt. > > > > > > Signed-off-by: David Brown <davidb@xxxxxxxxxxxxxx> > > > > I've added your patch to my zImage patch queue. > > > > > With this change, I am able to boot MSM8x60 combining ATAGS and my DT. > > > It seems to work as long as my device tree has placeholders for all of > > > the properties I need. > > > > I think those missing nodes should simply be created if missing. I > > however don't see any function in the libfdt API to do that -- there is > > fdt_add_subnode() but no fdt_add_node(). Any DT expert please? > > fdt_add_subnode() will create a new node as you require. The > "subnode" is just supposed to indicate that the parameters are in the > form of the offset of the parent node and the new node's immediate > name, rather than taking a full path name for the new node. Sure... but I'm still a total nincompoop with regard to FDT. Let's suppose I do: offset = fdt_path_offset(fdt, "/memory"); but that returns -FDT_ERR_NOTFOUND. Now what? If I look at the documentation for fdt_add_subnode(): /** * fdt_add_subnode - creates a new node * @fdt: pointer to the device tree blob * @parentoffset: structure block offset of a node * @name: name of the subnode to locate * [...] I have no node offset, and can't find the offset for the parent of an nonexistent node. Should I use 0 for parentoffset here? I'm guessing that "/memory" is at the top level so there is just no parent. > > Also, should the DTB be enlarged in order to add new nodes, or even > > modify existing ones with larger properties? In other words, > > should something like fdt_move(fdt, fdt, fdt_totalsize(fdt)+HEADROOM) be > > used beforehand? > > Yes, you will need to do this, fdt_open_into() is the function you > want. Without making room first, adding nodes or expanding existing > properties will return -FDT_ERR_NOSPACE. Once you've made whatever > edits you need, you can use fdt_pack() to collapse the tree back to > its minimum size. Excellent! FRom a quick code inspection, fdt_open_into() appears to be fine with both the source and destination pointers being the same, right? > Although this is somewhat awkward, this approach is a deliberate > design decision, to avoid making libfdt dependent on a working general > purpose allocator, which may not be available when libfdt is used in > very limited environments such as a firmware/bootloader. This is perfect. The environment where I want to use this code is fairly limited indeed. Nicolas -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
