Re: [PATCH v4 1/2] drivers/s390/char: Add Ultravisor io device

[Janosch Frank]

On 5/18/22 13:47, Heiko Carstens wrote:
> On Tue, May 10, 2022 at 02:47:23PM +0000, Steffen Eiden wrote:
> > diff --git a/drivers/s390/char/Kconfig b/drivers/s390/char/Kconfig
> > index 6cc4b19acf85..e9b9902abbaf 100644
> > --- a/drivers/s390/char/Kconfig
> > +++ b/drivers/s390/char/Kconfig
> > @@ -100,6 +100,16 @@ config SCLP_OFB
> >   	  This option enables the Open-for-Business interface to the s390
> >   	  Service Element.
> >   
> > +config S390_UV_UAPI
> > +	def_tristate y
> > +	prompt "Ultravisor userspace API"
> > +	help
> > +	  Selecting exposes parts of the UV interface to userspace
> > +	  by providing a misc character device at /dev/uv.
> > +	  Using IOCTLs one can interact with the UV.
> > +	  The device is only available if the Ultravisor
> > +	  Facility (158) is present.
>
> Is there a reason why this is default "y"? If you think this should be
> compiled into the kernel if used, then why allow to make it a module
> at all?
> Instead you could get rid of a couple if lines of code.

There was a lot of discussion around this already and the "Y" was chosen 
as auto-loading this is a pain and therefore the SCLP and CHSC-Misc set 
it to Y and we took that as an example (Steffen spoke to Peter to get 
guidance).

I'm sure that we want the possibility to have this as a module. 
Personally I'd choose "m" over "y" since the module is only useful for a 
very small amount of users.