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SubjectRe: Adding kmap_atomic_prot_pfn

* Thomas Hellström <> wrote:

> Ingo Molnar wrote:
>> * Thomas Hellström <> wrote:
>>> Keith,
>>> What you actually are doing here is claiming copyright on code that
>>> other people have written, and tighten the export restrictions.
>>> kmap_atomic_prot_pfn() appeared long ago in drm git with identical
>>> code and purpose, but with different authors, and iounmap_atomic is
>>> identical to kunmap_atomic.
>>>> +EXPORT_SYMBOL_GPL(iomap_atomic_prot_pfn);
>> you want to use this facility in a binary-only driver?
>> Ingo
> At this point I have no such use for it, no.
> The original user was a MIT style licenced driver.

okay, then just to put this question to rest: i wrote the original
32-bit highmem code ~10 years ago. I wrote the first version of fixmap
support - in fact i coined the term. I wrote the first version of the
atomic-kmap facility as well.

All of that code is licensed under the GPLv2. So if anyone wants to make
any copyright claims about highmem/kmap/fixmap derivative works,
consider it in that light.

Regarding this new API variant that Keith wrote: it would be silly and
dangerous to export it anywhere but to in-kernel drivers. The API
disables preemption on 32-bit and rummages deep in the guts of the
kernel as well, uses up a precious resource (fixmap slots), etc. It's
internal and we eventually might want to deprecate forms of it and
concentrate on the good 64-bit performance side.

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