Re: [PATCH 02/13] dmaengine: Introduce dma_request_slave_channel_compat_reason()

Peter Ujfalusi
2015-06-22T11:31:20Z

On 06/12/2015 03:58 PM, Vinod Koul wrote:
> Sorry this slipped thru

I was away for a week anyways ;)

> Thinking about it again, I think we should coverge to two APIs and mark the
> legacy depracuated and look to convert folks and phase that out

Currently, w/o this series we have these APIs:
/* to be used with DT/ACPI */
dma_request_slave_channel(dev, name) /* NULL on failure */
dma_request_slave_channel_reason(dev, name) /* error code on failure */

/* Legacy mode only - no DT/ACPI lookup */
dma_request_channel(mask, fn, fn_param) /* NULL on failure */

/* to be used with DT/ACPI or legacy boot */
dma_request_slave_channel_compat(mask, fn, fn_param, dev, name) /* NULL on
failure */

To request _any_ channel to be used for memcpy one has to use
dma_request_channel(mask, NULL, NULL);

If I did not missed something.

As we need different types of parameters for DT/ACPI and legacy (non DT/ACPI
lookup) and the good API names are already taken, we might need to settle:

/* to be used with DT/ACPI */
dma_request_slave_channel(dev, name) /* error code on failure */
- Convert users to check IS_ERR_OR_NULL() instead against NULL
- Mark dma_request_slave_channel_reason() deprecated and convert the current users

/* to be used with DT/ACPI or legacy boot */
dma_request_slave_channel_compat(mask, fn, fn_param, dev, name) /* error code
on failure */
- Convert users to check IS_ERR_OR_NULL() instead against NULL
- Do not try legacy mode if either OF or ACPI failed because of real error

/* Legacy mode only - no DT/ACPI lookup */
dma_request_channel_legacy(mask, fn, fn_param) /* error code on failure */
- convert users of dma_request_channel()
- mark dma_request_channel() deprecated

/* to be used to get a channel for memcpy for example */
dma_request_any_channel(mask) /* error code on failure */
- Convert current dma_request_channel(mask, NULL, NULL) users
I know, any of the other function could be prepared to handle this when
parameters are missing, but it is a bit cleaner to have separate API for this.

It would be nice to find another name for the
dma_request_slave_channel_compat() so with the new name we could have chance
to rearrange the parameters: (dev, name, mask, fn, fn_param)

We would end up with the following APIs, all returning with error code on failure:
dma_request_slave_channel(dev, name);
dma_request_channel_legacy(mask, fn, fn_param);
dma_request_slave_channel_compat(mask, fn, fn_param, dev, name);
dma_request_any_channel(mask);

What do you think?

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