Re: [PATCH 1/4] of: Add of_parse_phandle_with_opt_args() helper function

From: Marc Zyngier
Date: Wed Sep 30 2015 - 05:09:15 EST

On 29/09/15 18:28, Rob Herring wrote:
> On Tue, Sep 22, 2015 at 12:52 PM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote:
>> of_parse_phandle_with_args() is slightly inflexible as it doesn't
>> allow the (unusual) case where the #*-cells property is not defined.
>> In order to support this, introduce of_parse_phandle_with_opt_args()
>> which assumes that #*-cells is zero when it is not defined,
> zero or cell_count - 1?

Zero is how the lack of #msi-cells property is interpreted. (cell_count
- 1) is how this is implemented.

> I would be okay with always assuming zero rather than being an error
> if that simplifies things. It is not really the kernel's job to be a
> dtb validator.

I'd be fine with that too. I'd just like it to be a defined behaviour,
not an unexpected side effect.

> Also, I assume this was done for some compatibility? In general, we
> should be explicit, so "#msi-cells = <0>" should be recommended and we
> should update dts files if they are not.

I agree that over time, we should update the existing DTS. But I hear
Mark chanting "Stable DT" behind me, so I'm inclined to provide an
transition path... ;-)

I'll respin the series later today.


Jazz is not dead. It just smells funny...
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at