Re: [PATCH] arm: Add Kconfig entry to select CONFIG_DTB_FILE

[Michal Orzel <michal.orzel@xxxxxxx>]

On 08.03.2021 14:13, Jan Beulich wrote:
> On 08.03.2021 14:11, Michal Orzel wrote:
>>
>>
>> On 08.03.2021 12:28, Jan Beulich wrote:
>>> On 08.03.2021 12:02, Michal Orzel wrote:
>>>> On 08.03.2021 11:00, Jan Beulich wrote:
>>>>> On 08.03.2021 10:52, Michal Orzel wrote:
>>>>>> +config DTB_FILE
>>>>>> +        string "Absolute path to device tree blob"
>>>>>> +        default ""
>>>>>> +        depends on LINK_DTB
>>>>>> +        ---help---
>>>>>> +          When using a bootloader that has no device tree support or 
>>>>>> when there
>>>>>> +          is no bootloader at all, use this option to specify the 
>>>>>> absolute path
>>>>>> +          to a device tree that will be linked directly inside Xen 
>>>>>> binary.
>>>>>
>>>>> How is selecting LINK_DTB but leaving DTB_FILE at an empty string
>>>>> different from not having a LINK_DTB setting at all?
>>>>>
>>>> LINK_DTB acts as a switch to allow setting the dtb path. Not having 
>>>> LINK_DTB option will result in
>>>> a build failure each time the user does not want to embed dtb into 
>>>> Xen(DTB_FILE is empty).
>>>
>>> Which isn't any different from having LINK_DTB and leaving the
>>> string empty, is it? I.e. imo no improved user experience.
>>>
>>>> I do not see why someone would want to select LINK_DTB leaving DTB_FILE as 
>>>> an empty string.
>>>
>>> People may not "want" to, but simply think accepting the default
>>> is fine, considering they've already said to link in some DTB.
>>> It may be obvious to you that there's no good default here, but
>>> it may not be to the person configuring their Xen. I'm guessing
>>> here, but did you try leaving out the default line? Would this
>>> make kconfig insist on the person to type in something? (Likely
>>> an empty string would still be accepted. As would be a relative
>>> path, despite what the help text says; I guess some forms of
>>> relative paths may even work.)
>>>
>> There is no option here to make kconfig insist on person to type something.
>> There is one solution. If I change in here:
>> https://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/arch/arm/Makefile;h=16e6523e2cc6072b7d4cbcdeaf4726b7a9b1d381;hb=HEAD#l71
>> from:
>> ifdef CONFIG_DTB_FILE
>> to:
>> ifneq ($(CONFIG_DTB_FILE),"")
>> then if user selects LINK_DTB but does not provide dtb path, the dtb will 
>> not be embedded into Xen.
> 
> I think this would be preferable plus eliminate the need for the
> separate LINK_DTB option.
> 
Will do this and send as v2
> Jan
> 
Michal