On 12/19/2017 05:02 PM, Daniel Vetter wrote: > On Tue, Dec 19, 2017 at 4:41 PM, Max Staudt <mstaudt@xxxxxxx> wrote: >> On 12/19/2017 02:57 PM, Daniel Vetter wrote: >>> The problem is that defio is totally not how a real driver works. >> >> But they do exist and I can't ignore them. >> >> I'm afraid I don't understand - why are those, such as xenfb, not real drivers? > > I mean kms drivers. The problem is that the magic mapping that fbdev > expects is real pain. Everyone else, including kms, expects an > explicit flush operation. So instead of hacking around even more with > the defio corner cases that don't work, I'm suggesting we just add > that flush operation. At least internally. > > Fixing kms drivers to implement a better defio is probably not a > reasonable investement of time. Ah yes, I understand now, you mean that KMS drivers have explicit flush, and defio is a hack to retrofit such drivers to an API that never supported a flush operation (the fbdev API), but always used to expose the video memory directly. Right? If yes, then I agree. Fixing the defio in the KMS drivers wouldn't even solve my problem - I'd still need to implement flush. So might as well care about the flush straight away, yep! >>> So >>> preferrably bootsplash would use kms directly, and use the explict dirtyfb >>> callback. >> >> Sure, if I'd be hooking into drmcon, that would be great. >> >> But drmcon doesn't exist yet, so it doesn't get us further to talk about a bootsplash on KMS :( >> >> I'm hooking into the in-kernel terminal emulator, because the bootsplash is a functional extension of that. It just happens that fbcon sits on top of FB, so I work with what I get. > > Why do you need a console for a boot splash? You're not drawing > console output afaiui ... And even your current fbdev-based > implementation only interfaces with fbcon insofar as you're making > sure fbcon doesn't wreak your boot splash. Or I'm missing something > somewhere. Errr... true. I'll answer it below, where you ask again. >> In fact, if I define fbops->flush(), defio drivers can still add their own proper flushing function, so everybody wins. I like that, see below. > > tbh I'd forget about ever touching any of the existing fbdev drivers. > Imo just not worth the time investement. Fair point. It's optional anyway, and can still be done (quickly and painlessly) on demand. Since my goal here is making a nice bootsplash, I'll touch as few drivers as I can. >>>> So, what shall I do? As it is, the hack is already specific to devices that really, really need it. >>>> >>>> Would you like me to extend the FB API or not? >>> >>> Yes. Well for real I'd like you to do kms, so maybe you need to explain >>> why exactly you absolutely have to use fbdev (aka which driver isn't >>> supported by drm that you want to enable this on). >> >> See Oliver's reply - we have plenty of fb-only systems deployed in the real world. Think Xen. Think AArch64 with efifb. Think any system before the KMS driver is loaded (which is a case that the splash is supposed to handle). > > And you need a real pretty boot-splash on those? That sounds all like > servers, and I haven't yet seen a request for real pretty&fast boot > splash for servers. Yeah, every little helps. And the vesafb/efifb case is valid for all of the desktop/laptop machines as well. >> Also, where would I hook into KMS, were I to implement it on top of KMS right now? I'm not working on top of FB per se, but on top of fbcon. So in a KMS world I wouldn't work on KMS itself, but on top of... drmcon, which doesn't exist. > > Hm, I guess I need to double check again, but I don't get why you need > to sit on top of a console for the boot splash. I mean I understand > that you need to shut up the console when the boot splash is on, but > from a quick look you're not using fbcon to render anything or > otherwise tie into it. Where's the connection? Fair point. So the case you're looking at is someone who wants to have a bootsplash, yet doesn't want to have fbcon. Correct? I agree, this is a case that is not covered with the current code. However such a generic solution would require the definition of new semantics of both fbcon and the bootsplash fighting for the same FB device - well, as long as no graphical application uses it. Urgh... It is a lot simpler to just dual-purpose fbcon, since it knows when to shut up on its own. And I simply assume that those who load a bootsplash file into their initramfs won't be short a few bytes to compile in fbcon as well. So... I've hooked into fbcon for simplicity's sake, so I don't have up to three parties fighting for the same device, and so I don't have to define semantics and interfaces to solve that conflict. Max _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
