On Thu Jun 5, 2025 at 4:20 PM CEST, Jan Beulich wrote:
> On 05.06.2025 16:15, Alejandro Vallejo wrote:
>> On Mon Jun 2, 2025 at 4:24 PM CEST, Jan Beulich wrote:
>>> On 02.06.2025 16:19, Alejandro Vallejo wrote:
>>>> On Mon Jun 2, 2025 at 9:51 AM CEST, Jan Beulich wrote:
>>>>> On 30.05.2025 14:02, Alejandro Vallejo wrote:
>>>>>> --- a/xen/include/asm-generic/device.h
>>>>>> +++ b/xen/include/asm-generic/device.h
>>>>>> @@ -6,9 +6,7 @@
>>>>>>
>>>>>> enum device_type
>>>>>> {
>>>>>> -#ifdef CONFIG_HAS_DEVICE_TREE
>>>>>> DEV_DT,
>>>>>> -#endif
>>>>>
>>>>> Why would this enumerator need exposing on a non-DT arch? In fact I would
>>>>> have
>>>>> hoped for ...
>>>>
>>>> A non-DT arch would not include this. x86 doesn't.
>>>
>>> Both here and ...
>>>
>>>>>> DEV_PCI
>>>>>
>>>>> ... this to be hidden for arch-es not supporting PCI.
>>>>>
>>>>> Similar concerns elsewhere in this change.
>>>>
>>>> This file is exclusively used by arches supporting DT to abstract away
>>>> where
>>>> the device came from. x86 does not use it at all, and while it wouldn't be
>>>> impossible to compile-out DEV_PCI, it would needlessly pollute the
>>>> codebase with
>>>> no measurable gain, because the abstractions still need to stay.
>>>
>>> ... here: In "xen/include/asm-generic/device.h" there's nothing at all
>>> saying
>>> that this file is a DT-only one. Instead there is something in there saying
>>> that it's suitable to use in the entirely "generic" case.
>>>
>>> Jan
>>
>> Try to use it from x86 and observe the build system catch fire. It could be
>> made
>> to not go on fire, but it implies heavy refactoring in x86 (particularly
>> IOMMU
>> code) for no good reason because there's no devices in a DTB to disambiguate.
>>
>> How about adding this to the top of the header?
>>
>> ```
>> /*
>> * This header helps DTB-based architectures abstract away where a
>> particular
>> * device comes from; be it the DTB itself or enumerated on a PCI bus.
>> */
>>
>> [snip]
>>
>> #ifndef CONFIG_HAS_DEVICE_TREE
>> #error "Header meant to be used exclusively by DTB-base architectures."
>> #endif
>> ```
>
> Might be fine, together with giving the file a name somewhat referring to DT.
>
> Jan
That would bring it out of sync with x86's asm/device.h. Both of them define
device_t and doing so in differently named headers would just be confusing for
everyone.
Cheers,
Alejandro
