Re: [PATCH net-next] misc: Add Renesas Synchronization Management Unit (SMU) support

On Tue, Feb 16, 2021 at 6:10 PM Min Li [off-list ref] wrote:

quoted

quoted

If I come up with a new file and move all the abstraction code there,
does that work?

I think so, but it's more important to figure out a good user space interface
first. The ioctl interfaces should be written on a higher-level abstraction, to
ensure they can work with any hardware implementation and are not
specific to Renesas devices.

Can you describe on an abstract level how a user would use the character
device, and what they achieve by that?

This driver is meant to be used by Renesas PTP Clock Manager for
Linux (pcm4l) software for Renesas device only.

About how pcm4l uses the char device, pcm4l will open the device
and do the supported ioctl cmds on the device, simple like that.

At the same time, pcm4l will also open ptp hardware clock device,
which is /dev/ptp[x], to do clock adjustments.

I can't help but think you are evading my question I asked. If there is no
specific action that this pcm4l tool needs to perform, then I'd think
we should better not provide any interface for it at all.

I also found a reference to only closed source software at
https://www.renesas.com/us/en/software-tool/ptp-clock-manager-linux
We don't add low-level interfaces to the kernel that are only
usable by closed-source software.

Once you are able to describe the requirements for what pcm4l
actually needs from the hardware, we can start discussing what
a high-level interface would look like that can be used to replace
the your current interface, in a way that would work across vendors
and with both pcm4l and open-source tools that do the same job.

      Arnd