On Thu, Feb 18, 2016 at 9:34 PM, Lukas Wunner <lukas@xxxxxxxxx> wrote: > >> Ok, makes sense. I still think adding the check to the client_register >> function would be good, just as a safety measure. > > Hm, the idea of calling vga_switcheroo_client_probe_defer() twice > causes me pain in the stomach. It's surprising for drivers which > just don't need it at the moment (amdgpu and snd_hda_intel) and > it feels like overengineering and pampering driver developers > beyond reasonable measure. Also while the single existing check is > cheap, we might later on add checks that take more time and slow > things down. It's motivated by Rusty's API Manifesto: http://sweng.the-davies.net/Home/rustys-api-design-manifesto With the mandatory check in _register we reach level 5 - it'll blow up at runtime when we try to register it. Without that the failure is completely silent, and you need to read the right mailing list thread (level 1), but at least the kerneldocs lift it up to level 3. For more context: We have tons of fun with EPROBE_DEFER handling between i915 and snd-hda, and I'm looking into all possible means to make any api/subsystem using deferred probing as robust as possible by default. One of the ideas is to inject deferred probe failures at runtime, but that's kinda hard to do in a generic way. At least making it as close to impossible to abuse as feasible is the next best option. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe platform-driver-x86" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
