On Wed, Aug 26, 2026 at 06:37:00PM +0530, Ekansh Gupta wrote:
On 20-08-2026 20:17, Rob Clark wrote:
On Wed, Aug 19, 2026 at 11:15 PM Krzysztof Kozlowski krzk@kernel.org wrote:
On 19/08/2026 17:48, Rob Clark wrote:
On Wed, Aug 19, 2026 at 8:27 AM Krzysztof Kozlowski krzk@kernel.org wrote:
The rule of usptream development is that we do not accept duplicated code, just because a vendor wants to write something new. This is basically the concept applied all over the drivers tree, where we pushed back against all sorts of duplications all over the vendors.
What I miss in this thread is why would there be any exception here. We do not grant exceptions from standard practices on "I want" reasons.
I agree that we should not have duplicated drivers just for vendor lolz. But when it comes to adopting common frameworks and integrating better into the ecosystem, this doesn't seem like something we should actively discourage. I don't think this is a case of vendor lolz, but
No one discourages it. Following standard Linux kernel practices and requirements is not discouraging, do not twist the narrative here. Again, it is standard upstream review telling that we do not duplicate drivers. Ever, unless there is serious exception needed.
I wasn't trying to twist the narrative, just trying to come up with a path forward that isn't "no" or "improve existing driver", since neither of those gets us towards a future using common frameworks.
I asked why there should be an exception granted? Is the reason for exception following: "We want to adopt common framework" ?
Possibly? But I don't think we want two drivers to be any sort of long term solution. (Ie. as long as venus/iris have co-exist.)
rather reacting to drm/accel emerging as the standard framework for this sort of driver.
So how do we get from here to there?
What is wrong with my proposal?
Maybe I missed something, my understanding was your proposal was "Grow/replace/improve existing driver instead of coming with a duplicate".. grow or improve doesn't move us toward common frameworks. Maybe "replace" is a valid option. If there is something I missed, then I apologize.
Options I can think of are:
- Hardware cutoff.. new hw gets new driver, existing hw gets existing driver
- Backwards compat chardev registered by new driver, providing existing UABI. I'm not 100% sure about the feasibility/drawbacks of this.. AFAIU the fastrpc folks where planning a backwards compat layer in userspace, so maybe it is possible.
- exception?
I'd like to know what the feasibility of #2 is, since at a high level that sounds like the best option. Possibly limit exposure of legacy UABI to existing hw so we don't get into a place of needing to extend the legacy UABI for new hw?
But #1 sounds like a non-controversial place to start regardless. Possibly with #2 coming as followup and necessary step before eventual migration to new driver for existing hw?
Even if we start with #2, how do we handle first-merge-window bugs/regressions without reverting addition of new driver and removal of old? It seems like we'd need a window of a couple release cycles where both drivers exist?
Maybe others have other/better options in mind?
To all, I'm seeking on the approach I should follow to go ahead here. I can work on implementing #1(as per Rob's list) with hw specific compatible for v4 if it's acceptable.
I don't see any reason for you to define a "hw specific compatible", because as you have shown in this series (and as Rob point out), there's no difference in the "hardware".
The only reason for your "hw specific compatible" is to make a software selection in Linux - and that's not what DeviceTree is for.
As such, I don't see that you have a DeviceTree problem at all, because this is a Linux-internal problem.
#2(compat driver) is something that we are still exploring as we couldn't find any standard way to achieve it. We might start a separate discussion for that once we have few possible designs with us.
This is the actual problem!
We have existing user space that depends on the ioctl interface exposed by the current misc driver. You must not break these.
Hardware cutoff is not a viable solution, because that's just a declaration that we'll let the old platforms rotten - or alternatively you commit to maintain two drivers to the very same feature and quality level.
So the only reasonable solution is #2; from there it's a valid question if you reach that point my stepwise migrating the current misc driver that solution, or if you present a new driver with the fully backwards compatible interface, alongside the new ABI.
But this does bring to a question which the cover letter should explain - but doesn't: what problem does this patch series actually solve?
Regards, Bjorn
Happy to take any other suggestion also.>
BR, -R