[Qemu-devel] [PATCH v4 4/4] devicetree: update documentation for fw_cfg ARM bindings

Gabriel L. Somlo somlo at cmu.edu
Wed Nov 18 15:54:49 EST 2015

On Wed, Nov 18, 2015 at 02:04:24PM +0100, François Revol wrote:
> On 17/11/2015 23:14, Rob Herring wrote:
> > On Mon, Nov 16, 2015 at 2:38 AM, Paolo Bonzini <pbonzini at redhat.com> wrote:
> >>
> >>
> >> On 15/11/2015 03:07, Rob Herring wrote:
> >>> We generally don't want DT docs to depend on other kernel documentation.
> >>
> >> DT docs do not contain a copy of the data sheets, either.  There is no
> >> reason to say how to use the device (and even then, only doing so
> >> partially) in the DT docs.
> > 
> > The difference is datasheets apply to all OS's, kernel documentation
> > does not. In theory at least this could be used for other OS's, right?
> Would be nice indeed, as it's part of their intended purpose.
> For now we have to shoehorn things into linux-only stuff (like initrd)
> because well, nobody cares enough about NetBSD to compile U-Boot with
> its internal API, so let alone adding custom Haiku code.
> And of course, for things linux doesn't care about (like framebuffer
> description) then we're stuck trying to guess where it's at and writing
> drivers for our bootloader.
> So if at least people were considering they aren't the only users of
> this, that'd make life better for everyone.
> > Perhaps QEMU is the right place to thoroughly describe this and DT and
> > sysfs docs can refer to it.
> The brilliant idea of FDT was that we could have a canonical source and
> blob for it where people could send patches, but of course Linux and BSD
> freaks disagreed, so you now find Linux-flavoured DTs for rPi and other
> things, as well as BSD versions.
> Please, at least get the binding documentation for this unique and
> usable for everyone!

That would be 'docs/specs/fw_cfg.txt' in the QEMU source tree. I will
avoid cut'n'pasting anything from there into either the proposed
Documentation/ABI/testing/sysfs-firmware-qemu_fw_cfg (leaving only the
sysfs specific bits in there), and also remove any redundant bits from

I'm inclined to add (in v5) a mention of 'qemu:docs/specs/fw_cfg.txt'
to both the proposed fw_cfg sysfs doc file, and to the existing fw_cfg
arm/dt node doc file, unless I get strong objections against doing so... :)


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