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RCVD_VIA_SMTP_AUTH(0.00)[]; TAGGED_RCPT(0.00)[dt]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:mid,suse.de:dkim,suse.de:email,imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo] X-Spam-Score: -3.01 X-Spam-Level: Hi Am 30.06.25 um 09:26 schrieb Hans de Goede: > Hi, > > On 30-Jun-25 8:34 AM, Thomas Zimmermann wrote: >> Hi >> >> Am 28.06.25 um 13:50 schrieb Krzysztof Kozlowski: >>> On 27/06/2025 13:34, Thomas Zimmermann wrote: >>>> Hi >>>> >>>> Am 27.06.25 um 10:08 schrieb Krzysztof Kozlowski: >>>>> On Mon, Jun 23, 2025 at 08:44:45AM +0200, Luca Weiss wrote: >>>>>> Document the interconnects property which is a list of interconnect >>>>>> paths that is used by the framebuffer and therefore needs to be kept >>>>>> alive when the framebuffer is being used. >>>>>> >>>>>> Acked-by: Thomas Zimmermann >>>>>> Signed-off-by: Luca Weiss >>>>>> --- >>>>>>    Documentation/devicetree/bindings/display/simple-framebuffer.yaml | 3 +++ >>>>>>    1 file changed, 3 insertions(+) >>>>>> >>>>>> diff --git a/Documentation/devicetree/bindings/display/simple-framebuffer.yaml b/Documentation/devicetree/bindings/display/simple-framebuffer.yaml >>>>>> index 296500f9da05e296dbbeec50ba5186b6b30aaffc..f0fa0ef23d91043dfb2b220c654b80e2e80850cd 100644 >>>>>> --- a/Documentation/devicetree/bindings/display/simple-framebuffer.yaml >>>>>> +++ b/Documentation/devicetree/bindings/display/simple-framebuffer.yaml >>>>>> @@ -79,6 +79,9 @@ properties: >>>>>>      power-domains: >>>>>>        description: List of power domains used by the framebuffer. >>>>>>    +  interconnects: >>>>>> +    description: List of interconnect paths used by the framebuffer. >>>>>> + >>>>> maxItems: 1, or this is not a simple FB anymore. Anything which needs >>>>> some sort of resources in unknown way is not simple anymore. You need >>>>> device specific bindings. >>>> In this context, 'simple' means that this device cannot change display >>>> modes or do graphics acceleration. The hardware itself is not >>>> necessarily simple. As Javier pointed out, it's initialized by firmware >>> If hardware is not simple, then it needs specific bindings. >>> >>>> on the actual hardware. Think of 'VGA-for-ARM'. We need these resources >>>> to keep the display working. >>> I don't claim you do not need these resources. I claim device is not >>> simple thus does not suit rules for generic bindings. Generic bindings >>> are in general not allowed and we have them only for very, very simple >>> devices. >>> >>> You say this is not simple device, so there you go - specific binding >>> for this complex (not-simple) device. >> No, I didn't. I said that the device is simple. I did not say that the device's hardware is simple. Sounds nonsensical, but makes sense here. The simple-framebuffer is just the range of display memory that the firmware configured for printing boot-up messages. We use it for the kernel's output as well.  Being generic and simple is the exact raison d'etre for simple-framebuffer.  (The display property points to the actual hardware, but we don't need it.) > I believe part of the problem here is the simple part of the simplefb > name in hindsight that is a mistake and we should have called the thing > firmware-framebuffer since its goal is to pass along a firmware setup > framebuffer to the OS for displaying stuff. I totally feel you. In DRM land, we've also been upset about the naming. But well... > > As for the argument for having a firmware-framebuffer not being allowed > because framebuffers are to complex to have a generic binding, that > ship has long sailed since we already have the simplefb binding. > > And since we already have the binding I do not find this not being > simple a valid technical argument. That is an argument to allow > having a generic binding at all or to not have it at all, but here > we already have the binding and this is just about evolving the binding > with changing hw needs. Exactly my point. > > And again this reminds me very much of the whole clocks / regulators > addition to simplefb discussion we had over a decade ago. Back then > we had a huge thread, almost a flamefest with in my memory over > a 100 emails and back then the only argument against adding them > was also "it is not simple", which IMHO really is a non argument for > an already existing binding. Certainly it is not a good technical > argument. > > During the last decade, after clocks and regulators were added to > the binding. simplefb has been used successfully on millions (billions?) > handover the firmware framebuffer to the OS for bootsplash use, > replacing various vendor hacks for this. Disallowing the addition of > interconnect support to the simplefb binding will only result in > various vendor hacks appearing in vendor kernels for this, which > I believe is something which we should try to avoid. Exactly. And I'd also add that the current way of handling the situation is the only feasible one. Simple-framebuffer needs to be generic and compatible with existing and future hardware at minimal cost. The way of doing so, is to have a few properties, such as clocks, regulators and now interconnects, that the firmware clearly tells us about.  If we go with per-hardware/per-vendor nodes, simple-framebuffer loses its usefulness. > > So as the maintainer of the simplefb kernel driver for over a decade > I strongly advice the DT maintainers to accept this bindings patch As the maintainer of the simpledrm driver, I second this. Best regards Thomas > and from my my side this still is: > > Reviewed-by: Hans de Goede > > Regards, > > Hans > > -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)