Re: [PATCH] arm64: dts: stingray: use NUM_SATA to configure number of sata ports

From: Florian Fainelli
Date: Wed Jun 13 2018 - 20:47:02 EST

On 06/13/2018 01:18 PM, Scott Branden wrote:
> Hi Rob,
> Thanks for comment - reply inline.
> On 18-06-13 12:31 PM, Florian Fainelli wrote:
>> On 06/12/2018 03:54 PM, Rob Herring wrote:
>>> On Thu, Jun 7, 2018 at 12:53 PM, Scott Branden
>>> <scott.branden@xxxxxxxxxxxx> wrote:
>>>> Hi Rob,
>>>> Could you please kindly comment on change below.
>>>> It allows board variants to be added easily via a simple define for
>>>> different number of SATA ports.
>>>> On 18-06-04 09:22 AM, Florian Fainelli wrote:
>>>>> On 05/18/2018 11:34 AM, Scott Branden wrote:
>>>>>> Move remaining sata configuration to stingray-sata.dtsi and enable
>>>>>> ports based on NUM_SATA defined.
>>>>>> Now, all that needs to be done is define NUM_SATA per board.
>>>>> Rob could you review this and let us know if this approach is okay or
>>>>> not? Thank you!
>>>>>> Signed-off-by: Scott Branden <scott.branden@xxxxxxxxxxxx>
>>>>>> ---
>>>>>> diff --git a/arch/arm64/boot/dts/broadcom/stingray/stingray-sata.dtsi
>>>>>> b/arch/arm64/boot/dts/broadcom/stingray/stingray-sata.dtsi
>>>>>> index 8c68e0c..7f6d176 100644
>>>>>> --- a/arch/arm64/boot/dts/broadcom/stingray/stingray-sata.dtsi
>>>>>> +++ b/arch/arm64/boot/dts/broadcom/stingray/stingray-sata.dtsi
>>>>>> @@ -43,7 +43,11 @@
>>>>>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ #address-cells = <1>;
>>>>>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ #size-cells = <0>;
>>>>>> +#if (NUM_SATA > 0)
>>>>>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ status = "okay";
>>>>>> +#else
>>>>>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ status = "disabled";
>>>>>> +#endif
>>> This only works if ports are contiguously enabled (0-N). You might not
>>> care, but it is not a pattern that works in general.
> Correct - all board designs that include this dtsi file follow such
> commonality (ie. design with SATA0 first, etc). By having common board
> designs it allows for commonality in dts files rather than duplicating
> information everywhere. If somebody designs a bizarro board they are
> free to create their own dts file of course.
>>> Â And I'm not a fan
>>> of C preprocessing in DT files in general beyond just defines for
>>> single numbers.
> The use of a define to specify the number of SATA ports in the board
> design meets our requirements of being able to maintain many boards. We
> need a method to specify the number of ports in the board design rather
> than copying and pasting the information in many dts files. If you have
> an alternative upstreamable mechanism to manage the configuration of
> many boards without copy and paste that would be ideal?

We had discussed this off-list, but I really think you should be having
some sort of higher level scripting engine which is able to generate
valid per-board DTS files and not have the kernel and its use of the C
pre-processor attempt to solve your problems because a) it's the wrong
place, and b) it is limited.