On Mon, May 11, 2020 at 1:43 PM Lukas Wunner <lukas@xxxxxxxxx> wrote: > > On Mon, May 11, 2020 at 11:54:33AM +0200, Daniel Vetter wrote: > > - One unfortunate thing with drm_dev_unplug is that the driver core is > > very opinionated and doesn't tell you whether it's a hotunplug or a > > driver unload. In the former case trying to shut down hw just wastes > > time (and might hit driver bugs), in the latter case driver engineers > > very much expect everything to be shut down. > > You can get that information at the PCI bus level with > pci_dev_is_disconnected(). The flag queried by this function is set > upon hot removal. Be aware however that the device is guaranteed to > be unreachable if the function returns true, but the converse is NOT > guaranteed, i.e. the function may return false even though the device > has just gone away. > > Those somewhat difficult semantics are one of the reasons why some > people are skeptical of the function's merits (notably Greg KH). > See this LWN article for more information: > > https://lwn.net/Articles/767885/ > (scroll down to the "Surprise removal" section) > > I've suggested to Greg a few years back that we should have a flag > at the device level to indicate whether it's gone, not just at the bus > level. That way the property could be expressed regardless of the bus > used. It would facilitate the feature you're missing, that the driver > core tells you whether it's a surprise removal or not. Unfortunately > Greg rejected the idea. Ok, so at least for pci devices you could do something like if (pci_dev_is_disconnected()) drm_dev_unplug(); else drm_dev_unregister(); In the ->remove callback and both users and developers should be happy. I guess for other drivers like usb/spi just yanking the cable for driver hacking is good enough - loss of power should also reset the device :-) -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
