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

[Greg KH]

On Wed, Sep 15, 2021 at 02:42:55PM +0000, Min Li wrote:
> > > > > +/*
> > > > > + * RSMU IOCTL List
> > > > > + */
> > > > > +#define RSMU_MAGIC '?'
> > > >
> > > > Where did you get this value from?
> > > >
> > > > Where did you reserve it?
> > >
> > > No I didn't reserve it. I checked other code and they all seem to use
> > > a random character
> > 
> > That's not the best way to do this.
> > 
> > Why do you need ioctls at all anyway?  What userspace tools will be
> > accessing this driver?  Do you have a link to where they are located at?
> 
> Hi Greg
> 
> The userspace tool is called PCM4L (PTP Clock Manager for Linux) from Renesas
> 
> https://www.renesas.com/us/en/software-tool/ptp-clock-manager-linux
> 
> But the functions of this misc driver is not ptp related. It is meant for being called by pcm4l to
> support GNSS assisted partial timing support (APTS), which doesn't have abstracted/dedicated
> Linux Kernel API's. That is why I went for IOCTL in the first place.

Why not work on a real set of apis for this type of thing so that all
devices of this type will work properly?

thanks,

greg k-h