Am 28.09.20 um 09:37 schrieb Thomas Zimmermann:

Hi

Am 28.09.20 um 08:50 schrieb Christian König:

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Am 27.09.20 um 21:16 schrieb Sam Ravnborg:

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Hi Thomas.

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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.

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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 thought this was for convenience. The important is_iomem bit is missing.

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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.

How do you call this within TTM?

ttm_bus_placement, but I really don't like that name.

The data structure represents a pointer to either system or I/O memory, but not necessatrily device memory. It contains raw data. That would give something like

struct databuf_map struct databuf_ptr struct dbuf_map struct dbuf_ptr

My favorite would be dbuf_ptr. It's short and the API names would make sense: dbuf_ptr_clear() for clearing, dbuf_ptr_set_vaddr() to set an address, dbuf_ptr_incr() to increment, etc. Also, the _ptr indicates that it's a single address; not an offset with length.

Puh, no idea. All of that doesn't sound like it 100% hits the underlying meaning of the structure.

Christian.

Best regards Thomas

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Christian.

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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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