Re: [Xen-devel] [PATCH v4 6/6] xen: arm: Import of_bus PCI entry from Linux (as a dt_bus entry)

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Fri, 2015-07-03 at 11:47 +0100, Ian Campbell wrote:
> On Fri, 2015-06-26 at 20:08 +0200, Julien Grall wrote:
> > Hi Ian,
> > 
> > On 08/05/2015 13:27, Ian Campbell wrote:
> > > This provides specific handlers for the PCI bus relating to matching
> > > and translating. It's mostly similar to the defaults but includes some
> > > additional error checks and other PCI specific bits.
> > 
> > I though the previous patch (#5) was enough to handle PCI. May I ask why 
> > we need it?
> 
> There are some subtle differences in how the generic code vs. the pci
> specific code here will handle buggy DTs (i.e. #*-cells which are not as
> required by the pci bindings). This will mean we tolerate such device
> trees better.
> 
> I say "buggy", but actually it's not clear to me from reading "PCI Bus
> Binding to Open Firmware" that when the device_type is "pci" that
> #*-cells shouldn't be assumed to have the values given in that text,
> e.g. the text says "The value of "#address-cells" for PCI Bus Nodes is
> 3." and not "A PCI Bus Node must contain a #address-cells property
> containing 3". Maybe that interpretation is bogus, but with this patch
> we are are able to cope with DTs written by people who do read it like
> that.
> 
> FWIW it also gets us the ability to parse the flags (cacheability),
> although at the moment we only check them for validity rather than use
> them.

I've pasted a slightly adjusted version of this into the commit message
for v5.
> 
> > > Functions/types renamed and reindented (because apparently we do
> > > that for these).
> > 
> > My mistake, when I first port the functions from Linux I changed the 
> > name and the coding style to match the existent functions in 
> > xen/common/device_tree.c
> > 
> > All the functions to work directly on the DT blob have been moved in a 
> > separate file (arch/arm/bootfdt.c), so this file is mostly Linux code. 
> > I'm thinking to resync it correctly for Xen 4.7.
> 
> That sounds good, thanks.
> 
> > 
> > > Needs a selection of IORESOURCE_* defines, which I've taken from Linux
> > > and have included locally for now until we figure out where else they
> > > might be needed.
> > 
> > Regards,
> > 
> 
> 
> 
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