Messages in this thread | | | Date | Tue, 23 Jul 2019 09:57:24 +0200 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH v2] driver core: Remove device link creation limitation |
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On Tue, Jul 23, 2019 at 09:34:54AM +0200, Rafael J. Wysocki wrote: > Hi Greg, > > On Tue, Jul 16, 2019 at 5:21 PM Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > > > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > Subject: [PATCH] driver core: Remove device link creation limitation > > > > If device_link_add() is called for a consumer/supplier pair with an > > existing device link between them and the existing link's type is > > not in agreement with the flags passed to that function by its > > caller, NULL will be returned. That is seriously inconvenient, > > because it forces the callers of device_link_add() to worry about > > what others may or may not do even if that is not relevant to them > > for any other reasons. > > > > It turns out, however, that this limitation can be made go away > > relatively easily. > > > > The underlying observation is that if DL_FLAG_STATELESS has been > > passed to device_link_add() in flags for the given consumer/supplier > > pair at least once, calling either device_link_del() or > > device_link_remove() to release the link returned by it should work, > > but there are no other requirements associated with that flag. In > > turn, if at least one of the callers of device_link_add() for the > > given consumer/supplier pair has not passed DL_FLAG_STATELESS to it > > in flags, the driver core should track the status of the link and act > > on it as appropriate (ie. the link should be treated as "managed"). > > This means that DL_FLAG_STATELESS needs to be set for managed device > > links and it should be valid to call device_link_del() or > > device_link_remove() to drop references to them in certain > > sutiations. > > > > To allow that to happen, introduce a new (internal) device link flag > > called DL_FLAG_MANAGED and make device_link_add() set it automatically > > whenever DL_FLAG_STATELESS is not passed to it. Also make it take > > additional references to existing device links that were previously > > stateless (that is, with DL_FLAG_STATELESS set and DL_FLAG_MANAGED > > unset) and will need to be managed going forward and initialize > > their status (which has been DL_STATE_NONE so far). > > > > Accordingly, when a managed device link is dropped automatically > > by the driver core, make it clear DL_FLAG_MANAGED, reset the link's > > status back to DL_STATE_NONE and drop the reference to it associated > > with DL_FLAG_MANAGED instead of just deleting it right away (to > > allow it to stay around in case it still needs to be released > > explicitly by someone). > > > > With that, since setting DL_FLAG_STATELESS doesn't mean that the > > device link in question is not managed any more, replace all of the > > status-tracking checks against DL_FLAG_STATELESS with analogous > > checks against DL_FLAG_MANAGED and update the documentation to > > reflect these changes. > > > > While at it, make device_link_add() reject flags that it does not > > recognize, including DL_FLAG_MANAGED. > > > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > Reviewed-by: Saravana Kannan <saravanak@google.com> > > Tested-by: Marek Szyprowski <m.szyprowski@samsung.com> > > Do I need to resend this? > > I know that posting new things during a merge window is not most > convenient, sorry about that.
No, it's in my queue, give me a few days to dig out from my huge pending patch list, no need to resend it.
thanks,
greg k-h
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