On Thu, Mar 31, 2016 at 10:17:46AM -0500, Rob Herring wrote:
> On Thu, Mar 31, 2016 at 12:22 AM, David Gibson
> <david@xxxxxxxxxxxxxxxxxxxxx> wrote:
> > On Wed, Mar 23, 2016 at 07:40:19PM -0500, Rob Herring wrote:
> >> In preparation to support bus specific checks, add the necessary
> >> infrastructure to determine the bus type for nodes. Initially, PCI and
> >> simple bus are supported.
> >>
> >> Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
> >> ---
> >> David,
> >
> > Sorry it's taken me a while to look at this. I've been a mixture of
> > busy and sick :/
>
> No problem.
>
> [...]
>
> >> +static bool is_pci_bridge(struct node *node)
> >> +{
> >> + struct property *prop;
> >> +
> >> + if (!node)
> >> + return false;
> >> +
> >> + prop = get_property(node, "device_type");
> >> + if (!prop)
> >> + return false;
> >> +
> >> + if (strcmp(prop->val.val, "pci") == 0)
> >> + return true;
> >> +
> >> + return false;
> >> +}
> >
> > So, I don't love using device_type here, since that's generally
> > discouraged in modern flat trees, but I don't know of a better way to
> > detect a pci bridge, so I guess it's ok.
>
> True, but pci, cpu, and memory remain as accepted uses. We'd have to
> define a "pci-bridge" or "pci-bus" compatible to replace it.
Right, that was the conclusion I was coming around to.
> >> +struct bus_type pci_bus_type = {
> >> + .expected_addr_cells = 3,
> >> + .expected_size_cells = 2,
> >
> > I'm a bit torn here. Part of me wants to suggest a 'check_bridge'
> > function which handles this and can also make more subtle checks, but
> > then just the expected cells values will handle nearly all real cases
> > more succinctly.
>
> I left them as you had them, but I'm not so sure these are all that
> useful. It works for PCI as the sizes are fixed, but then we could
> just check against fixed values. For simple-bus, we need more
> flexibility because the size could be 1 or 2. For other cases like I2C
> or SPI buses, we know the sizes, but we can't really detect those
> buses.
Hm, ok. Well how about instead of the expected cells values, we have
two callbacks: check_bridge() and check_device(). The
check_bridge() callback can check the cells parameters along with
anything else that makes sense.
--
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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