Re: Does Xenomai 3.2.x work with 4.14.x kernels?

[Jan Kiszka <jan.kiszka@siemens.com>]

On 13.04.22 11:25, Scott Reed via Xenomai wrote:
> Hello,
> 
> I am trying to build a 4.14.110 kernel+ipipe+xenomai_3.2.7 and running into
> issues when trying to compile. Namely, the 4.14.x kernel does not seem
> to understand the "__kernel_timespec" struct.
> 
> Is it known if Xenomai 3.2.x works with 4.14.x kernels?

We stopped supporting 4.14.x actively, and we apparently broke backward
compatibility at some point. Locally likely fixable, but not
maintainable for upstream anymore.

> 
> Some background information
> ---------------------------
> Our platform is based on an ARM iMx6q.
> 
> I have tried to move to a 5.4.x kernel, but ran into another issue
> in that we have an RTDM driver which uses PCI MSI interrupts and
> when I try to register the interrupt with rtdm_irq_request the
> function returns EINVAL(-22).
> 
> When working with a vanilla 5.4.x kernel and non-RTDM version of
> the driver, there are no issues when registering the interrupt.
> 
> I started to dive into this problem, but saw that as of kernel
> 4.16, the PCI MSI interrupts for our platform have been changed
> to be handled as chained interrupts.
> 
> In this forum, I have seen multiple discussions and patches regarding
> chained interrupts for X86, but not for ARM and began to think that
> maybe chained interrupt support in xenomai is not complete for ARM.
> 
> Could this be the case?

In fact, those patches are for ARM and not x86 (the latter was always
fine). Please check latest ipipe-arm releases, or even dovetail (5.10+).

> 
> For this reason, I backed down to the 4.14.x kernel, but now have run
> into the compiling issue as mentioned at the start of this email.

When starting something new, do not use outdated kernels anymore.

> 
> One last piece of background information, my initial motivation to move
> to a new xenomai was that we moved to GCC 10.2 (in the meantime GCC 11.1)
> and I was concerned regarding the ARM r7 register clobbering issues/patches
> posted to the forum as I am fighting against a bug in our system where 
> registers get corrupted albeit not r7 (typically r0 with a value of 
> 0xFFFFFFFA (-38)). This problem seems to have come in after we upgraded
> to GCC 10.2

If you are in hurry and have a working version based on older things,
moving backward can be a valid intermediate options. But thinking ahead,
using a mixture of old (kernel) and new (xenomai, toolchain) components
is almost never a good idea: You are to far from mainstream, and piece
will fill off left and right.

Jan

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Siemens AG, Technology
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