policy on externs

policy on externs

[Justin Skists]

Hi,

What is the kernel policy on using "extern" to share variables between
source files in a module?

I've been looking at one subsystem in staging [that shares variables quite a
bit] to becoming familar with it, and seeing if I can help do some work on it
in my free time.

Personally I prefer to see them eradicated (they polute the namespace), and
store such variables in a context structure that is passed around. But I don't
see any reference about it in the coding style, and I am not one to
code-churn just because it's not my personal style! :)


Thanks,
Justin

policy on externs

[Greg KH]

On Sat, Jun 02, 2018 at 05:23:20PM +0100, Justin Skists wrote:
> Hi,
> 
> What is the kernel policy on using "extern" to share variables between
> source files in a module?
> 
> I've been looking at one subsystem in staging [that shares variables quite a
> bit] to becoming familar with it, and seeing if I can help do some work on it
> in my free time.
> 
> Personally I prefer to see them eradicated (they polute the namespace), and
> store such variables in a context structure that is passed around. But I don't
> see any reference about it in the coding style, and I am not one to
> code-churn just because it's not my personal style! :)

context structures are almost always best, as they can be tied to the
hardware device, not the module itself.  So yes, if they can be
eradicated, please do so.

What driver are you looking at?

thanks,

greg k-h

policy on externs

[Justin Skists]

On Sat, Jun 02, 2018 at 07:33:46PM +0200, Greg KH wrote:
> On Sat, Jun 02, 2018 at 05:23:20PM +0100, Justin Skists wrote:
> > Hi,
> > 
> > What is the kernel policy on using "extern" to share variables between
> > source files in a module?
> > 
> > I've been looking at one subsystem in staging [that shares variables quite a
> > bit] to becoming familar with it, and seeing if I can help do some work on it
> > in my free time.
> > 
> > Personally I prefer to see them eradicated (they polute the namespace), and
> > store such variables in a context structure that is passed around. But I don't
> > see any reference about it in the coding style, and I am not one to
> > code-churn just because it's not my personal style! :)
> 
> context structures are almost always best, as they can be tied to the
> hardware device, not the module itself.  So yes, if they can be
> eradicated, please do so.

OK, Greg. I'll have another look at it, then.

> What driver are you looking at?

I have been looking at the speakup subsystem.


Thanks,
Justin.