Re: [RFC PATCH RESEND v2] of/pci: Provide support for parsing PCIDT ranges property

From: Thomas Petazzoni
Date: Thu Mar 21 2013 - 12:06:38 EST

Dear Andrew Murray,

On Fri, 1 Mar 2013 12:23:36 +0000, Andrew Murray wrote:
> This patch factors out common implementations patterns to reduce overall kernel
> code and provide a means for host bridge drivers to directly obtain struct
> resources from the DT's ranges property without relying on architecture specific
> DT handling. This will make it easier to write archiecture independent host bridge
> drivers and mitigate against further duplication of DT parsing code.
> This patch can be used in the following way:
> struct of_pci_range_iter iter;
> for_each_of_pci_range(&iter, np) {
> //directly access properties of the address range, e.g.:
> //iter.pci_space, iter.pci_addr, iter.cpu_addr, iter.size or
> //iter.flags
> //alternatively obtain a struct resource, e.g.:
> //struct resource res;
> //range_iter_fill_resource(iter, np, res);
> }
> Additionally the implementation takes care of adjacent ranges and merges them
> into a single range (as was the case with powerpc and microblaze).
> The modifications to microblaze, mips and powerpc have not been tested.
> v2:
> This follows on from suggestions made by Grant Likely
> (
> Signed-off-by: Andrew Murray <Andrew.Murray@xxxxxxx>
> Signed-off-by: Liviu Dudau <Liviu.Dudau@xxxxxxx>

Thanks, I've tested this successfully with the Marvell PCIe driver. I'm
about to send a new version of the Marvell PCIe patch set that includes
this RFC proposal.

I only made two small changes compared to your version, detailed below.

> +#define for_each_of_pci_range(iter, np) \
> + for (; of_pci_process_ranges(iter, np);)

In the initial part of the loop, I added a memset() to initialize to
zero the "iter" structure. Otherwise, if you forget to do it before
calling of_pci_process_ranges(), it may crash (depending on the random
values present in the uninitialized structure).

> +#define range_iter_fill_resource(iter, np, res) \
> + do { \
> + res->flags = iter.flags; \
> + res->start = iter.cpu_addr; \
> + res->end = iter.cpu_addr + iter.size - 1; \
> + res->parent = res->child = res->sibling = NULL; \
> + res->name = np->full_name; \
> + } while (0)

And here, I enclosed all the usage of the macro parameters in
parenthesis. Like (res)->flags instead of res->flags. If you don't do
that, then passing &foobar as the 'res' parameter causes some
compilation failure because &foobar->res is not valid, while
(&foobar)->res is.

Best regards,

Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
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