Re: [PATCH v2 00/22] mfd: demodularization of non-modular drivers

[Charles Keepax <ckeepax@opensource.cirrus.com>]

On Wed, Dec 05, 2018 at 12:48:47PM +0100, Linus Walleij wrote:
> On Wed, Dec 5, 2018 at 12:36 PM Charles Keepax
> <ckeepax@opensource.cirrus.com> wrote:
> > On Sun, Dec 02, 2018 at 11:23:07PM -0500, Paul Gortmaker wrote:
> > > The solution to #4 is similar - we delete the ".remove" function and
> > > the binding into the platform_driver struct.  However, since the same
> > > ".remove" function could also be triggered by an "unbind" (such as for
> > > pass-through of a device to a guest instance)  - so we also explicitly
> > > disable any unbind for the driver.
> > >
> > > The unbind mask allows us to ensure we will see if there was some odd
> > > corner case out there that was relying on it.  Typically it would be a
> > > multi-port ethernet card passing a port through to a guest, so a
> > > sensible use case in MFD drivers seems highly unlikely.  This same
> > > solution has already been used in multiple other mainline subsystems.
> > >
> >
> > I guess if this is a general direction thing, but it does seem
> > that module unload is not the only reason one might ever unbind a
> > driver. So are we sure we want to remove the option to unbind
> > these drivers? Certainly for testing it is sometimes useful.
> 
> I personally never understood why these attributes are even
> present on non-modular drivers.
> 
> If testing is about exercising unbind/bind to reintialize
> the code through a new call to .probe(), why would the developer
> not take it all the way through and make it a module?
> It just looks like a half-measure.
> 

Well I guess in someways it is a half-measure. I vaguely seem to
remember some dependency nightmare that can make it really hard
to have the MFD allowed as a module in some cases, I can't
remember the exact details but probably why some of these are not
modules.

I certainly don't strongly object to removing the ability to
unbind these drivers, just wanted to make sure everyone is
aligned that it's a good thing to do. Does kinda remove a couple
of debugging options (debugging things like drivers interfering
with each other) and the last chance restart the driver and see
if that helps rescue something.

Thanks,
Charles