Re: [PATCH V1 17/29] xen/arm: Mark each device used by Xen as disabled in DOM0 FDT

[Julien Grall <julien.grall@linaro.org>]

On 09/09/2013 12:37 PM, Ian Campbell wrote:
> On Wed, 2013-08-28 at 15:47 +0100, Julien Grall wrote:
>> When a device has a property status with disabled inside, Linux will not use
>> the device.
>
> Do we not filter such devices out already?

We only filter gic/timer node. All the others nodes used by Xen, for 
instance the serial device, will be marked by status = "disabled".

> Or did the previous patch remove that functionality? In which case is
> there a bisection hazard here?

AFAIK, there is no bisection hazard with the current order of this patch 
series.

>
> Why is it preferred to leave the device with disabled in it instead of
> removing it? (Can this go in the changelog please)
> I think I've asked before, but is the handling of status = disabled
> generic and therefore reliable?

I let this patch because I didn't implement all the fake nodes in the 
previous patch series. In another hand, I'm not sure how Linux will 
react if there is a missing node and it should cope with status = 
"disabled" with most of nodes.

I will give a try and see if I can remove completely nodes used by Xen. 
Except, of course, gic and timer nodes which are recreated later.

>>
>> Signed-off-by: Julien Grall <julien.grall@linaro.org>
>> ---
>>   xen/arch/arm/domain_build.c |    8 ++++++++
>>   1 file changed, 8 insertions(+)
>>
>> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
>> index 76decf4..d56bc70a 100644
>> --- a/xen/arch/arm/domain_build.c
>> +++ b/xen/arch/arm/domain_build.c
>> @@ -208,6 +208,14 @@ static int write_properties(struct domain *d, struct kernel_info *kinfo,
>>               return res;
>>       }
>>
>> +    /* Disable all devices used by Xen */
>> +    if ( dt_device_used_by(np) == DOMID_XEN )
>> +    {
>> +        res = fdt_property(kinfo->fdt, "status", "disabled", 8 + 1);
>> +        if ( res )
>> +            return res;
>> +    }
>> +
>>       /*
>>        * XXX should populate /chosen/linux,initrd-{start,end} here if we
>>        * have module[2]
>
>


-- 
Julien Grall