On Wed, Aug 27, 2014 at 10:55 AM, Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx> wrote: >> >> Is simplefb something that should be in the device tree distinctly in >> >> the first place - shouldn't it be a subset of the functionality of the >> >> video nodes? It's the same hardware being driven differently. >> > >> > Therorically, yes, but that would mean knowing beforehand what the >> > final binding will look like, even before submitting the driver. Since >> > the bindings are always reviewed, and most of the time changed >> > slightly, that wouldn't work very well with the DT as a stable ABI >> > policy I guess. >> >> If you don't know how the bindings for a device will look like at the time of >> writing your DTS, you're always screwed, whether you add a simpefb >> node or not. >> >> If you know how the bindings look like, just add the device, with an extra >> "linux,simplefb" compatibility value. >> If you don't know how the bindings look like, do your utter best in >> guessing. Your DTS must be amended later anyway, either because >> you guessed wrong[*] (in case you added a node to have simplefb >> working), or because you have to add a real device node (in case you >> didn't add one for simplefb). > > Let's be conservative and consider the case where we would guess > wrong. > > If we just rely on a simplefb node, when reviewing and integrating the > "new" bindings to describe accureately the various IPs involved in the > display path, we would obviously create new compatibles for > them. Since it's new compatibles, we can come up with any binding we'd > like, without have to consider the backward compatibility, since it's > a new binding. > > Then, we just remove the simplefb, all is good. I would keep the simplefb compatible value. Else you break compatibility with old kernels that don't have your new driver. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe linux-fbdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html