On 8/2/2022 10:31 PM, Jason Gunthorpe wrote: > On Tue, Aug 02, 2022 at 10:57:55AM -0600, Alex Williamson wrote: >> On Tue, 2 Aug 2022 13:35:04 -0300 >> Jason Gunthorpe <jgg@xxxxxxxxxx> wrote: >> >>> On Tue, Aug 02, 2022 at 09:41:28AM -0600, Alex Williamson wrote: >>> >>>> The subtlety is that there's a flag and a field and the flag can only >>>> be set if the field is set, the flag can only be clear if the field is >>>> clear, so we return -EINVAL for the other cases? Why do we have both a >>>> flag and a field? This isn't like we're adding a feature later and the >>>> flag needs to indicate that the field is present and valid. It's just >>>> not a very clean interface, imo. Thanks, >>> >>> That isn't how I read Abhishek's proposal.. The eventfd should always >>> work and should always behave as described "The notification through >>> the provided eventfd will be generated only when the device has >>> entered and is resumed from a low power state" >>> >>> If userspace provides it without LOW_POWER_REENTERY_DISABLE then it >>> still generates the events. >>> >>> The linkage to LOW_POWER_REENTERY_DISABLE is only that userspace >>> probably needs to use both elements together to generate the >>> auto-reentry behavior. Kernel should not enforce it. >>> >>> Two fields, orthogonal behaviors. >> >> What's the point of notifying userspace that the device was resumed if >> it might already be suspended again by the time userspace responds to >> the eventfd? > > I don't know - the eventfds is counting so it does let userspace > monitor frequency of auto-sleeping. > > In any case the point is to make simple kernel APIs, not cover every > combination with a use case. Decoupling is simpler than coupling. > > Jason Thanks Alex and Jason for your inputs. It seems, I can use the original uAPI where we will have 2 variants of ENTRY. Since already kernel merge window is started, so I will wait for v5.20-rc1 (or v6.0-rc1) and then I will rebase and test my patches on the updated kernel. Regards, Abhishek
