On Mon, Dec 18, 2017 at 11:20:38AM +0000, Grant Likely wrote: > On Mon, Dec 18, 2017 at 4:34 AM, David Gibson > <david@xxxxxxxxxxxxxxxxxxxxx> wrote: > > On Tue, Dec 12, 2017 at 12:48:10PM +0000, Grant Likely wrote: > >> On Tue, Dec 12, 2017 at 6:14 AM, David Gibson > >> <david@xxxxxxxxxxxxxxxxxxxxx> wrote: > >> > On Tue, Nov 28, 2017 at 11:57:09AM +0000, Grant Likely wrote: > >> >> The current code throws away all the data type and grouping information > >> >> when parsing the DTS source file, which makes it difficult to > >> >> reconstruct the data format when emitting a format that can express data > >> >> types (ie. dts and yaml). Use the marker list to mark the beginning and > >> >> end of each integer array block (<> and []), the datatype contained in > >> >> each (8, 16, 32 & 64 bit widths), and the start of each string. > >> >> > >> >> At the same time, factor out the heuristic code used to guess a property > >> >> type at emit time. It is a pretty well defined standalone block that > >> >> could be used elsewhere, for instance, when emitting YAML source. Factor > >> >> it out into a separate function so that it can be reused, and also to > >> >> simplify the write_propval() function. > >> >> > >> >> When emitting, group integer output back into the same groups as the > >> >> original source and use the REF_PATH and REF_PHANDLE markers to emit the > >> >> the node reference instead of a raw path or phandle. > >> >> > >> >> Signed-off-by: Grant Likely <grant.likely@xxxxxxx> > >> > > >> > I'm a bit dubious how well forcing the marker mechanism to do all this > >> > stuff it was never intended for can work in the long term. Still, > >> > it's an interesting experiment. > >> > >> As long as the actual data is stored as flat buffer, the markers > >> mechanism works quite well for this. I tried doing something entirely > >> separate, and it turned out to be awful. Another alternative is to > >> break up the flat buffer into a chain of data blocks with attached > >> type information, but that is a very invasive change. > >> > >> This approach has the advantage of being robust on accepting both > >> typed and anonymous data. If the markers are not there then the > >> existing behaviour can be maintained, but otherwise it can emit a > >> higher fidelity of source language. > > > > Hm, true. The approach is growing on me. I guess what I'm still > > dubious about is how much this type annotation can get us to approach > > the YAML model. For example, YAML can distinguish between [ [1, 2], > > [3, 4] ] and [1, 2, 3, 4] which isn't really feasible in dtc. > > To start with I'm constraining what is permissible in the YAML > encoding. So, even though YAML can encode multiple nested lists, I'm > not permitting that in this iteration. To take an example: > > in dts: reg = <0x1000 0x100> <0x4000 0x300>; > In YAML I'm encoding as: reg: [ [0x1000, 0x100], [0x4000, 0x300] ] > > in dts: compatible = "acme,uart9000", "ns16550" > is in YAML: compatible: [ "acme,uart9000", "ns16550"] > > in dts: #size-cells = <1>; > in YAML: "#size-cells": [ [ 1 ] ] > > in dts: uint16-prop = /bits/ 16 <31>; > in YAML: uint16-prop: [ !uint16 [31] ] > > I'm not allowing anything outside that pattern. So, the following are > all disallowed currently: > reg: [0x1000, 0x100, 0x4000, 0x300] /* integers need to be in a list - > maps to <...> in dts */ > compatible: "ns16550" /* not encoded into list */ > reg: [ [ [0x4, 0xffff0000], 0x80000], [ [0x4, 0xfffe0000], 0x40000] ] > /* Triple nesting not allowed*/ Sorry, I meant to make a comment on this months ago, but never got around to it. In terms of the immediate problem here, this seems like a reasonable approach. However, it kind of underscores the lingering worries I have about using YAML as a DT encoding format. In the JSON/YAML world, 1 and [ [ 1 ] ] are different things, and using the later as a way of encoding what's essentially a plain integer would be pretty perverse. So, I'm concerned that if we have YAML front-and-centre to the user, it will be pretty misleading as to what is and isn't possible. -- 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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