On Wed, Dec 05, 2018 at 05:55:21AM -0700, Simon Glass wrote: > Hi David, > > On Mon, 3 Dec 2018 at 22:23, David Gibson <david@xxxxxxxxxxxxxxxxxxxxx> wrote: > > > > On Mon, Dec 03, 2018 at 11:20:17AM -0700, Simon Glass wrote: > > > Hi David, > > > > > > On Sun, 2 Dec 2018 at 18:11, David Gibson <david@xxxxxxxxxxxxxxxxxxxxx> wrote: > > > > > > > > On Wed, Nov 28, 2018 at 07:31:37PM -0700, Simon Glass wrote: > > > > > Hi Rob, > > > > > > > > > > On Wed, 28 Nov 2018 at 14:51, Tom Rini <trini@xxxxxxxxxxxx> wrote: > > > > > > > > > > > > On Wed, Nov 28, 2018 at 03:47:22PM -0600, Rob Herring wrote: > > > > > > > On Wed, Nov 28, 2018 at 3:31 PM Tom Rini <trini@xxxxxxxxxxxx> wrote: > > > > > > > > > > > > > > > > On Sat, Nov 24, 2018 at 08:42:19PM +1100, David Gibson wrote: > > > > > > > > > On Wed, Nov 14, 2018 at 04:29:23PM -0800, Simon Glass wrote: > > > > > > > > > > Hi David, > > > > > > > > > > > > > > > > > > > > We had a discussion today about a possible new v18 DT format[1] > > > > > > > > > > > > > > > > > > > > You have seen Frank Rowand's design from January[2]. Frank presented > > > > > > > > > > material at the conference[3] and I wrote up something up too [4]. > > > > > > > > > > > > > > > > > > Yes, I didn't like the original proposal very much - overly > > > > > > > > > complicated, but the revised one I suggested back looks reasonably > > > > > > > > > do-able. > > > > > > > > > > > > > > > > > > Your proposal seems to have a rather different focus from Frank's - > > > > > > > > > his is mostly about cleaner handling of overlays and similar > > > > > > > > > extensions. Yours is mostly about size. > > > > > > > > > > > > > > > > > > Can I ask what's the concern here? I mean, first of all, I'm finding > > > > > > > > > it a bit hard to believe that a few kiB of device tree really mean > > > > > > > > > much in the context of a vaguely modern system. But more specifically > > > > > > > > > is the concern in-memory size? Or size on persistent storage, disk or > > > > > > > > > flash? Those two would be amenable to different approaches to > > > > > > > > > mitigate. > > > > > > > > > > > > > > > > So, with respect to size, yes, for one example, modern 32bit Allwinner > > > > > > > > SoCs are limited to either 32KiB or 24KiB and 64bit SoCs are limited to > > > > > > > > 32KiB and that's our space for residing and executing from and holding > > > > > > > > the device tree we're working from. > > > > > > > > > > > > > > You are referring to limits of what the bootROM can load for u-boot > > > > > > > SPL cases, right? > > > > > > > > > > > > Yes. > > > > > > > > So, I gather this SPL is essentially a first-stage bootloader? I'm > > > > > > Yes. > > > > > > > wondering if fdt is actually the right tool for the job here. Could > > > > you instead make just a hardcoded structure with the minimal known > > > > values that the first stage loader needs to find the second stage, > > > > which would include the full DT. I'm envisaging that you'd have some > > > > tool for building that first-stage structure from the fdt, but that > > > > would be done at build time, not runtime. > > > > > > This is the goal of the 'dtoc' tool in U-Boot. It creates header files > > > and structs to hold data from the DT. Would you be open to upstreaming > > > this? > > > > I guess. My first thought would be that such a tool would be more > > closely linked to the specific bootloader than the DT as such, but if > > it's widely useful enough then I'm happy to consider including it with > > dtc. > > OK. I think perhaps we could work with Zephyr to come up with a common solution. > > The current tool is Python. Is that acceptable or should it be C? As a build time tool, Python is fine. -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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