Hi Heikki, On Tue, 5 Sept 2023 at 11:50, Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx> wrote: > > Hi Dmitry, > > On Mon, Sep 04, 2023 at 12:41:39AM +0300, Dmitry Baryshkov wrote: > > The kdev->fwnode pointer is never set in drm_sysfs_connector_add(), so > > dev_fwnode() checks never succeed, making the respective commit NOP. > > That's not true. The dev->fwnode is assigned when the device is > created on ACPI platforms automatically. If the drm_connector fwnode > member is assigned before the device is registered, then that fwnode > is assigned also to the device - see drm_connector_acpi_find_companion(). > > But please note that even if drm_connector does not have anything in > its fwnode member, the device may still be assigned fwnode, just based > on some other logic (maybe in drivers/acpi/acpi_video.c?). > > > And if drm_sysfs_connector_add() is modified to set kdev->fwnode, it > > breaks drivers already using components (as it was pointed at [1]), > > resulting in a deadlock. Lockdep trace is provided below. > > > > Granted these two issues, it seems impractical to fix this commit in any > > sane way. Revert it instead. > > I think there is already user space stuff that relies on these links, > so I'm not sure you can just remove them like that. If the component > framework is not the correct tool here, then I think you need to > suggest some other way of creating them. The issue (that was pointed out during review) is that having a component code in the framework code can lead to lockups. With the patch #2 in place (which is the only logical way to set kdev->fwnode for non-ACPI systems) probing of drivers which use components and set drm_connector::fwnode breaks immediately. Can we move the component part to the respective drivers? With the patch 2 in place, connector->fwnode will be copied to the created kdev's fwnode pointer. Another option might be to make this drm_sysfs component registration optional. > Side note. The problem you are describing here is a limitation in the > component framework - right now it's made with the idea that a device > can represent a single component, but it really should allow a device > to represent multiple components. I'm not saying that you should try > to fix the component framework, but I just wanted to make a note about > this (and this is not the only problem with the component framework). > > I like the component framework as a concept, but I think it needs a > lot of improvements - possibly rewrite. Yes. There were several attempts to rewrite the component framework, but none succeeded up to now. Anyway, I consider rewriting components framework to be a bigger topic compared to drm connector fwnode setup. -- With best wishes Dmitry
