Re: [PATCH V4 8/8] cpufreq: Add Rust based cpufreq-dt driver

[Greg KH]

On Tue, Jul 16, 2024 at 05:15:25PM +0200, Danilo Krummrich wrote:
> On Thu, Jul 11, 2024 at 06:34:22PM +0200, Greg KH wrote:
> > On Thu, Jul 11, 2024 at 06:12:08PM +0200, Danilo Krummrich wrote:
> > > On Thu, Jul 11, 2024 at 04:37:50PM +0200, Greg KH wrote:
> > > > On Thu, Jul 11, 2024 at 03:21:31PM +0200, Danilo Krummrich wrote:
> > > > > (2) You require drivers to always implement a "dummy" struct platform_device,
> > > > > there is platform_device_register_simple() for that purpose.
> > > > 
> > > > No, NEVER do that.  platform devices are only for real platform devices,
> > > > do not abuse that interface any more than it already is.
> > > 
> > > I thought we're talking about cases like [1] or [2], but please correct me if
> > > those are considered abusing the platform bus as well.
> > > 
> > > (Those drivers read the CPU OF nodes, instead of OF nodes that represent a
> > > separate device.)
> > > 
> > > [1] https://elixir.bootlin.com/linux/latest/source/drivers/cpuidle/cpuidle-riscv-sbi.c#L586
> > > [2] https://elixir.bootlin.com/linux/latest/source/drivers/cpuidle/cpuidle-psci.c#L441
> > 
> > Yes, these are abuses of that and should be virtual devices as they have
> > nothing to do with the platform bus.
> 
> For those drivers, wouldn't it be better if proper devices would be derived from
> the CPU OF nodes directly? This seems to be a common problem for cpuidle and
> cpufreq drivers.

Yes they should.

> But it's quite a while ago I dealt with such drivers, maybe there are reasons
> not to do so.

I think people just got lazy :)

thanks,

greg k-h