On Wed, Jul 28, 2021 at 09:04:34AM +0200, Arnd Bergmann wrote:

On Wed, Jul 28, 2021 at 7:43 AM Christoph Hellwig [off-list ref] wrote:

quoted

On Tue, Jul 27, 2021 at 08:09:41PM -0300, Jason Gunthorpe wrote:

quoted

On Tue, Jul 27, 2021 at 03:54:40PM -0600, Alex Williamson wrote:

quoted

I'm still not happy with how this is likely to break users and even
downstreams when upgrading to a Kconfig with this change.

I've never heard of Kconfig as stable ABI. Christoph/Arnd, have you
heard of any cases where we want to keep it stable?

It isn't an ABI, but we really do try to avoid breaking if we can and
I rember Linus shouting at people if they did that for common options.

This is handled in very different ways depending on the maintainers,
some people go to great lengths to avoid breaking 'make oldconfig'
or 'make defconfig', others don't seem to mind at all.

CONFIG_USB_EHCI_TEGRA is an example of an option that was
left in place to help users of old config files, another one is
CONFIG_EXT3_FS. In both cases the idea is that the original
code was changed, but the old option left in place to point to
the replacement.

And here starts the problem, when people treat their obscure config
options as first class citizen. The exposure of CONFIG_EXT3_FS is
in magnitudes larger than CONFIG_USB_EHCI_TEGRA.

This is why I think that is generally bad idea to leave old config
options, most of the time such options will rotten for years till
someone actually will notice and delete them.

Thanks