Re: [PATCH v3 0/4] dma-buf: Flag vmap'ed memory as system or I/O memory

[Sam Ravnborg <sam@ravnborg.org>]

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.

 
> 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@ravnborg.org>

	Sam
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