Re: [MAINTAINERS SUMMIT] Device Passthrough Considered Harmful?

Ricardo Ribalda Delgado
2024-07-29T09:57:03Z

On Sun, Jul 28, 2024 at 1:24 PM Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> On Fri, Jul 26, 2024 at 05:40:50PM +0200, Ricardo Ribalda Delgado wrote:
> > On Fri, Jul 26, 2024 at 3:11 PM Laurent Pinchart
> > <laurent.pinchart@ideasonboard.com> wrote:
> > >
> > > On Fri, Jul 26, 2024 at 10:02:27AM +0200, Ricardo Ribalda Delgado wrote:
> > > > On Thu, Jul 25, 2024 at 9:44 PM Laurent Pinchart wrote:
> > > > > On Thu, Jul 25, 2024 at 04:20:35PM +0300, Leon Romanovsky wrote:
> > > > > > On Thu, Jul 25, 2024 at 03:02:13PM +0200, Ricardo Ribalda Delgado wrote:
> > > > > > > On Thu, Jul 25, 2024 at 2:23 PM Leon Romanovsky wrote:
> > > > > > > > On Thu, Jul 25, 2024 at 11:26:38AM +0200, Ricardo Ribalda Delgado wrote:
> > > > > > > > > On Wed, Jul 24, 2024 at 10:02 PM Laurent Pinchart wrote:
> > > > > > > >
> > > > > > > > <...>
> > > > > > > >
> > > > > > > > > It would be great to define what are the free software communities
> > > > > > > > > here. Distros and final users are also "free software communities" and
> > > > > > > > > they do not care about niche use cases covered by proprietary
> > > > > > > > > software.
> > > > > > > >
> > > > > > > > Are you certain about that?
> > > > > > >
> > > > > > > As a user, and as an open source Distro developer I have a small hint.
> > > > > > > But you could also ask users what they think about not being able to
> > > > > > > use their notebook's cameras. The last time that I could not use some
> > > > > > > basic hardware from a notebook with Linux was 20 years ago.
> > > > > >
> > > > > > Lucky you, I still have consumer hardware (speaker) that doesn't work
> > > > > > with Linux, and even now, there is basic hardware in my current
> > > > > > laptop (HP docking station) that doesn't work reliably in Linux.
> > > > > >
> > > > > > > > > They only care (and should care) about normal workflows.
> > > > > > > >
> > > > > > > > What is a normal workflow?
> > > > > > > > Does it mean that if user bought something very expensive he
> > > > > > > > should not be able to use it with free software, because his
> > > > > > > > usage is different from yours?
> > > > > > > >
> > > > > > > > Thanks
> > > > > > >
> > > > > > > It means that we should not block the standard usage for 99% of the
> > > > > > > population just because 1% of the users cannot do something fancy with
> > > > > > > their device.
> > > > > >
> > > > > > Right, the problem is that in some areas the statistics slightly different.
> > > > > > 99% population is blocked because 1% of the users don't need it and
> > > > > > don't think that it is "normal" flow.
> > > > > >
> > > > > > > Let me give you an example. When I buy a camera I want to be able to
> > > > > > > do Video Conferencing and take some static photos of documents. I do
> > > > > > > not care about: automatic makeup, AI generated background, unicorn
> > > > > > > filters, eyes recentering... But we need to give a way to vendors to
> > > > > > > implement those things closely, without the marketing differentiators,
> > > > > > > vendors have zero incentive to invest in Linux, and that affects all
> > > > > > > the population.
> > > > >
> > > > > I've seen these kind of examples being repeatedly given in discussions
> > > > > related to camera ISP support in Linux. They are very misleading. These
> > > > > are not the kind of features that are relevant for the device
> > > > > pass-through discussion these day. Those are high-level use cases
> > > > > implemented in userspace, and vendors can ship any closed-source
> > > > > binaries they want there. What I care about is the features exposed by
> > > > > the kernel to userspace API.
> > > >
> > > > The ISPs are gradually becoming programmable devices and they indeed
> > > > help during all of those examples.
> > >
> > > I'd like to see more technical information to substantiate this claim.
> > > So far what I've sometimes seen is ISPs that include programmable
> > > elements, but hiding those behind a firmware that exposes a fixed
> > > (configurable) pipeline. I've also heard of attempts to expose some of
> > > that programmability to the operating system, which were abandoned in
> > > the end due to lack usefulness.
> > >
> > > > Userspace needs to send/receive information from the ISP, and that is
> > > > exactly what vendors want to keep in the close.
> > >
> > > But that's exactly what we need to implement an open userspace ecosystem
> > > :-)
> > >
> > > > Describing how they implement those algorithms is a patent minefield
> > > > and their differentiating factor.
> > >
> > > Those are also arguments I've heard many times before. The
> > > differentiating factor for cameras today is mostly in userspace ISP
> > > control algorithms, and nobody is telling vendors they need to open all
> > > that.
> >
> > I disagree. The differentiating factor is what the ISP is capable of
> > doing and how they do it. Otherwise we would not see new ISPs in the
> > market.
>
> Hardware certainly evolves, but it's far from being the main
> differentiating factor in the markets and use cases you're usually
> referring to.
>
> > If you define the arguments passed to an ISP you are defining the
> > algorithm, and that is a trade secret and/or a patent violation.
>
> Are you confusing ISP processing blocks, sometimes referred to as
> algorithms, and ISP control algorithms ? There is absolutely no way to
> do anything with an ISP, not even the bare minimum, if you don't know
> what parameters to pass to it.

Any ISP released in the last few years has *hundreds of thousands* of
parameters.

We only modify hundreds of parameters during runtime. Those are the
ones we need to be documented.

If we enforce a "usable open camera stack", we will have the
documentation and the code needed to use the ISP.

Asking vendors to document *ALL* the parameters means describing how
they have implemented the internals of the ISP camera algorithms.

>
> > > When it comes to patents, we all know how software patents is a
> > > minefield, and hardware is also affected. I can't have much sympathy for
> > > this argument though, those patents mostly benefit the largest players
> > > in the market, and those are the ones who currently claim they can't
> > > open anything due to patents.
> >
> > Big players do not usually sue each other. The big problem is patent
> > trolls that "shoot at everything that moves".
> >
> > I dislike patents, but it is the world we have to live in. No vendor
> > is going to take our approach if they risk a multi million dollar
> > lawsuit.
>
> When was the last time anyone heard of big players pushing to reform the
> patent system ? At best there are initiatives such as OIN, which some
> large companies have supporting. It's still a workaround though.
>
> > > > > > > This challenge seems to be solved for GPUs. I am using my AMD GPU
> > > > > > > freely and my nephew can install the amdgpu-pro proprietary user space
> > > > > > > driver to play duke nukem (or whatever kids play now) at 2000 fps.
> > > > > > >
> > > > > > > There are other other subsystems that allow vendor passthrough and
> > > > > > > their ecosystem has not collapsed.
> > > > > >
> > > > > > Yes, I completely agree with you on that.
> > > > > >
> > > > > > > Can we have some general guidance of what is acceptable? Can we define
> > > > > > > together the "normal workflow" and focus on a *full* open source
> > > > > > > implementation of that?
> > > > > >
> > > > > > I don't think that is possible to define "normal workflow". Requirement
> > > > > > to have open-source counterpart to everything exposed through UAPI is a
> > > > > > valid one. I'm all for that.
> > > > >
> > > > > That's my current opinion as well, as least when it comes to the kernel
> > > > > areas I mostly work with.
>
> --
> Regards,
>
> Laurent Pinchart

--
Ricardo Ribalda