On Sun, Sep 03, 2023 at 04:53:42PM +0100, Russell King (Oracle) wrote: > On Fri, Sep 01, 2023 at 04:41:12PM -0700, Douglas Anderson wrote: > > Based on grepping through the source code this driver appears to be > > missing a call to drm_atomic_helper_shutdown() at system shutdown > > time. Among other things, this means that if a panel is in use that it > > won't be cleanly powered off at system shutdown time. > > > > The fact that we should call drm_atomic_helper_shutdown() in the case > > of OS shutdown/restart comes straight out of the kernel doc "driver > > instance overview" in drm_drv.c. > > > > This driver was fairly easy to update. The drm_device is stored in the > > drvdata so we just have to make sure the drvdata is NULL whenever the > > device is not bound. > > ... and there I think you have a misunderstanding of the driver model. > Please have a look at device_unbind_cleanup() which will be called if > probe fails, or when the device is removed (in other words, when it is > not bound to a driver.) > > Also, devices which aren't bound to a driver won't have their shutdown > method called (because there is no driver currently bound to that > device.) So, ->probe must have completed successfully, and ->remove > must not have been called for that device. > > So, I think that all these dev_set_drvdata(dev, NULL) that you're > adding are just asking for a kernel janitor to come along later and > remove them because they serve no purpose... so best not introduce > them in the first place. What would that hypothetical janitor clean up exactly? Code making sure that there's no dangling pointer? Doesn't look very wise to me. Maxime
