On 8/12/22 13:49, Philip Prindeville wrote:


On Aug 12, 2022, at 11:54 AM, Florian Fainelli <f.faine...@gmail.com> wrote:

One aspect I could see is take for instance a device that is widely popular 
amongst our user base as was TI's ar7 for instance a while back, and for which 
we might have done a Linux 5.4, or 5.10 version at the time but we do not wish 
to continue to maintain.


Per my previous email, that seems like something that the SoC manufacturer 
should be doing... Why is this our burden?


Totally agree that SoC manufacturers share a fair amount of responsibility, there is no substitute for upstream and it associated benefits, but it is a commitment, and you are not stranger to this world.

In terms of supporting a given piece of hardware though, I would decouple the timeline.

There is the initial effort required to support your SoC and its many products which largely involves writing architecture specific code sometimes, DTS files, clock/SPI/USB/NAND/Ethernet MAC/PHY/Switch/Wi-Fi drivers for the most part. You would typically target a LTS kernel version for that effort such that you amortize that effort over a few years to come until the next LTS, and if possible in the meantime try to get your patches upstream such that the next LTS requires fewer patches to be carried over.

Now, when new stable updates show up though, the amount of merge conflicts or SoC support code you need to adjust is minimal compared to the other parts of the kernel that got updated.

So back to my example, we could have invested out of tree support for TI AR7 up until 5.4 and then decided to put it into an EOL/deep maintenance mode. Updating the stable 5.4 kernel would unlikely change the amount of AR7 specific patches, so the maintenance cost could be fairly low.

Does that make sense?
--
Florian

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