On Friday 27 November 2015 10:29:39 Peter Ujfalusi wrote:
> struct dma_chan *dma_request_chan(struct device *dev, const char *name,
> const dma_cap_mask_t *mask);
> To request a slave channel. The mask parameter is optional and it is used
> to check if the received channel's capabilities can satisfy the requested
> mask. The dma_request_chan() will try to find the channel via DT, ACPI or
> in case if the kernel booted in non DT/ACPI mode it will use a filter
> lookup table and retrieves the RESOURCE_DMA from the requester's device.
> This legacy mode needs changes in platform code, in dmaengine drivers and
> finally the dmaengine user drivers can be converted:
I think we should not introduce the mask parameter at all. In the rare
case that we actually need to pass a mask other than DMA_SLAVE today,
we should be able to encode that in the data we pass to the filter
function.
> RESOURCE_DMA needs to be added to the platform devices with names
>
> For each dmaengine driver a string array listing the devices handled by the
> given DMA driver:
>
> static char *da8xx_edma0_devices[] = {
> "davinci-mcasp.0",
> "da830-mmc.0",
> };
>
> This information is going to be needed by the dmaengine driver, so
> modification to the platform_data is needed, and the driver map should be
> added to the pdata of the DMA driver:
However, a lot of drivers definitely need to pass a data pointer for
each device. I see that you currently rely on the IORESOURCE_DMA
method that a couple of platforms use today, but I think it would
be backwards to do it that way for the platforms that require passing
more than an integer number today.
Having a pointer as the filter function argument is intentional and I'd
prefer to change the platforms that currently use IORESOURCE_DMA (davinci,
pxa, omap1, blackfin, alchemy) to stop doing it instead, and return
IORESOURCE_DMA to its original meaning that was limited to ISAPNP style
devices not using the dmaengine API.
Arnd
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