[PATCH v2 1/2] dma: mmp_dma: add support for legacy transition

Daniel Mack [off-list ref] writes:

Hi Robert,

Thanks for pushing this topic :)
One minor nit:

quoted

+int mmp_pdma_toggle_reserved_channel(int legacy_channel)
+{
+	if (legacy_unavailable & (1 << legacy_channel))
+		return -EBUSY;
+	legacy_reserved ^= 1 << legacy_channel;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(mmp_pdma_toggle_reserved_channel);

My concern is that if pxa_request_dma() is called more than once for
whatever reason by a legacy implementation, the toggled bit mask might
get out of sync.

This is not possible.
The first call to pxa_request_dma() sets dma_channels[i].name to a non-NULL
value.
The second call to pxa_request_dma() cannot take the same i as
!dma_channels[i].name is not fullfilled.

As we know exactly on the caller site what we want to achieve, let's make the
API explicit with something like:

int mmp_pdma_set_reserved_channel(int legacy_channel, bool reserved)

Even if I have no strong opinion about it, I'll let the patch as it is, unless
you really want me to add the reserved parameter, in which case I'll release a
v3.

Cheers.

-- 
Robert