Re: [PATCH] nvmem: fix unregistering device in nvmem_register() error path

Greg Kroah-Hartman
2021-12-22T09:30:14Z

On Wed, Dec 22, 2021 at 10:16:20AM +0100, Rafał Miłecki wrote:
> On 22.12.2021 10:08, Johan Hovold wrote:
> > On Wed, Dec 22, 2021 at 10:00:03AM +0100, Rafał Miłecki wrote:
> > > On 22.12.2021 09:38, Johan Hovold wrote:
> >
> > > > It seems Rafał is mistaken here too; you certainly need to call
> > > > platform_device_put() if platform_device_register() fail, even if many
> > > > current users do appear to get this wrong.
> > >
> > > Yes I was! Gosh I made up that "platform_device_put()" name and only
> > > now I realized it actually exists!
> > >
> > > I stand by saying this design is really misleading. Even though
> > > platform_device_put() was obviously a bad example.
> > >
> > > Please remember I'm just a minor kernel developer however in my humble
> > > opinion behaviour of device_register() and platform_device_register()
> > > should be changed.
> > >
> > > If any function fails I expect:
> > > 1. That function to clean up its mess if any
> > > 2. Me to be responsible to clean up my mess if any
> > >
> > > This is how "most" code (whatever it means) works.
> > > 1. If POSIX snprintf() fails I'm not expected to call *printf_put() sth
> > > 2. If POSIX bind() fails I'm not expected to call bind_put() sth
> > > 3. (...)
> > >
> > > I'm not sure if those are the best examples but you should get my point.
> >
> > Yes, and we all agree that it's not the best interface. But it exists,
> > and changing it now risks introducing worse problem than a minor, mostly
> > theoretical, memleak.
>
> Thanks for confirming that, I was wondering if it's just my mind that
> doesn't find this design clear enough.
>
> Now, assuming this design isn't perfect and some purists would like it
> cleaned up:
>
> Would that make sense to introduce something like
> 1. device_register2() / device_add2()
> and
> 2. platform_device_register2() / platform_device_add2()
>
> that would *not* require calling *_put() on failure? Then start
> converting existing drivers to those new (clearner?) helpers?

See my other response, but no, this is not a good idea.
device_register() is correct as-is, but platform_device_register()
isn't.

thanks,

greg k-h