[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH 06/19] xen: Clean up asm-generic/device.h
On 05.06.2025 18:48, Alejandro Vallejo wrote: > 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. > > 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. Okay, then the name can't change. In which case the #ifdef-ary needs to remain, imo, to keep the header being "generic". Jan
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