Am 27.09.20 um 21:16 schrieb Sam Ravnborg:
Hi Thomas.
struct simap {
union {
void __iomem *vaddr_iomem;
void *vaddr;
};
bool is_iomem;
};
Where simap is a shorthand for system_iomem_map
And it could al be stuffed into a include/linux/simap.h file.
Not totally sold on the simap name - but wanted to come up with
something.
Yes. Others, myself included, have suggested to use a name that does not
imply a connection to the dma-buf framework, but no one has come up with
a good name.
I strongly dislike simap, as it's entirely non-obvious what it does.
dma-buf-map is not actually wrong. The structures represents the mapping
of a dma-able buffer in most cases.
With this approach users do not have to pull in dma-buf to use it and
users will not confuse that this is only for dma-buf usage.
There's no need to enable dma-buf. It's all in the header file without
dependencies on dma-buf. It's really just the name.
But there's something else to take into account. The whole issue here is
that the buffer is disconnected from its originating driver, so we don't
know which kind of memory ops we have to use. Thinking about it, I
realized that no one else seemed to have this problem until now.
Otherwise there would be a solution already. So maybe the dma-buf
framework *is* the native use case for this data structure.
We have at least:
linux/fb.h:
union {
char __iomem *screen_base; /* Virtual address */
char *screen_buffer;
};
Which solve more or less the same problem.
I also already noted that in TTM we have exactly the same problem and a
whole bunch of helpers to allow operations on those pointers.
Christian.
Anyway, if a better name than dma-buf-map comes in, I'm willing to
rename the thing. Otherwise I intend to merge the patchset by the end of
the week.
Well, the main thing is that I think this shoud be moved away from
dma-buf. But if indeed dma-buf is the only relevant user in drm then
I am totally fine with the current naming.
One alternative named that popped up in my head: struct sys_io_map {}
But again, if this is kept in dma-buf then I am fine with the current
naming.
In other words, if you continue to think this is mostly a dma-buf
thing all three patches are:
Acked-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
Sam
