Re: [Xen-devel] [PATCH v9 14/19] xen: introduce xenpv bus and a dummy pvcpu device

On 01/02/2014 03:43 PM, Roger Pau Monne wrote:
> Since Xen PVH guests doesn't have ACPI, we need to create a dummy
> bus so top level Xen devices can attach to it (instead of
> attaching directly to the nexus) and a pvcpu device that will be used
> to fill the pcpu->pc_device field.
> ---
>   sys/conf/files.amd64 |    1 +
>   sys/conf/files.i386  |    1 +
>   sys/x86/xen/xenpv.c  |  155 ++++++++++++++++++++++++++++++++++++++++++++++++++

I think it makes more sense to have 2 files: one for xenpv bus and one 
for a dummy pvcpu device. It would allow us to move xenpv bus to common 
code (sys/xen or sys/dev/xen).

[..]

> +
> +static int
> +xenpv_probe(device_t dev)
> +{
> +
> +	device_set_desc(dev, "Xen PV bus");
> +	device_quiet(dev);
> +	return (0);

As I understand, 0 means I can "handle" the current device, in this case 
if a device is probing, because it doesn't have yet a driver, we will 
use xenpv and end up with 2 (or even more) xenpv buses.

As we only want to probe xenpv bus once, when the bus was added 
manually, returning BUS_PROBE_NO_WILDCARD would suit better.

[..]

> +static int
> +xenpvcpu_probe(device_t dev)
> +{
> +
> +	device_set_desc(dev, "Xen PV CPU");
> +	return (0);

Same here: BUS_PROBE_NOWILDCARD.

-- 
Julien Grall