Hi,
>>>>Isn't the goal to make sure that for every kind of "struct device *"
> ^^^^^
>>>>it should be possible to use those dma_*() calls, without BUGging
>>>>out.
>>That sounds like a "yes", not a "no" ... except for devices on busses
> ^^^^^^
> Then it's not "every", which was your question. I guess I need
> to understand better how to interpret your questions.
My bad ... I meant "every" kind of device doing memory mapped I/O, which
is all that had been mentioned so far. This needs to work on more than
just the "platform bus"; "layered busses" shouldn't need special casing,
they are just as common. You had mentioned SCSI busses; USB, FireWire,
and others also exist. (Though I confess I still don't like BUG() as a
way to fail much of anything!)
That's likely a better way to present one of my points: if it's "generic",
then it must work on more than just the lowest level platform bus.
>>that don't have do memory mapped I/O. It's what I described: dma_*()
>>calls being used with struct device, without BUGging out.
>
>
> Let's see if we agree. The behavior I expect is:
>
> addr = dma_malloc(&some_usb_device->dev,size, &dma_addr,DMA_CONSISTENT)
> ===> BUG()
That's not consistent with what I thought what you said. USB devices
use memory mapped I/O, so this should work. (And using BUG instead
of returning null still seems wrong...)
However, we could agree that some kind of dma_malloc() should exist !!
> addr = dma_malloc(host_dev(some_usb_device), &dma_addr, DMA_CONSISTENT)
> ===> some consistent memory (or NULL).
>
> where host_dev would be something like:
>
> struct device *host_dev(struct usb_device *usbdev)
> {
> struct usb_hcd *hcd = usbdev->bus->hcpriv;
> return &hcd->pdev->device; /* actually, this would become &hcd->dev */
> }
Please look at the 2.5.53 tree with my "usbcore dma updates (and doc)"
patch, which Greg has now merged and submitted to Linus.
The pre-existing USB DMA API syntax did not change, so it looks only
"something" like what you wrote there.
- Dave
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This archive was generated by hypermail 2b29 : Tue Dec 31 2002 - 22:00:12 EST