On Mon, Apr 30, 2012 at 14:33, Mark Cave-Ayland
<mark.cave-ayl...@ilande.co.uk> wrote:
> On 30/04/12 15:03, Peter Maydell wrote:
>>> Therefore I can't change it to my (modified) sbus_mmio_map() function
>>> because it would break other non-SPARC platforms, and AIUI there is
>>> nothing
>>> in the memory API that allows me to move a subregion to a different
>>> MemoryRegion parent, even if I can get a reference to it with
>>> sysbus_mmio_get_region() after the sysbus_mmio_map() call - or have I
>>> misunderstood something?
>> Init functions like esp_init should be purely convenience functions
>> which create, set properties on, and map the sysbus/qdev device. If
>> they make use of private knowledge about the internals of the device
>> then this is wrong and should be fixed. For esp_init() it looks like
>> the handling of dma_memory_read, dma_memory_write, dma_opaque, it_shift
>> and dma_enabled are wrong.
>> If you fix that then you can just ignore the convenience function,
>> and create, configure and map the device as appropriate for you.
> Right I think I'm starting to understand this now - in which case it becomes
> a matter of just copying a handful of lines within sun4m which is more
> bearable.
> In your view, would a suitable fix be to change dma_memory_read,
> dma_memory_write, dma_opaque, it_shift and dma_enabled to be qdev properties
> and modify esp_init() to return the qdev reference so they can be set by the
> caller?

There's an ongoing work to introduce IOMMUs by changing how DMA work
and this could simplify the DMA part. There's no clean way to use
function pointers in qdev.

For it_shift, a qdev or QOM property should be OK.

The signal dma_enabled should be eventually replaced by a Pin.

> ATB,
> Mark.

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