On 11/15/2013 01:54 PM, Stephen Warren wrote:
> From: Stephen Warren <[email protected]>
>
> dma_request_slave_channel() simply returns NULL whenever DMA channel
> lookup fails. Lookup could fail for two distinct reasons:
>
> a) No DMA specification exists for the channel name.
> This includes situations where no DMA specifications exist at all, or
> other general lookup problems.
>
> b) A DMA specification does exist, yet the driver for that channel is not
> yet registered.
>
> Case (b) should trigger deferred probe in client drivers. However, since
> they have no way to differentiate the two situations, it cannot.
>
> Implement new function dma_request_slave_channel_or_err(), which performs
> identically to dma_request_slave_channel(), except that it returns an
> error-pointer rather than NULL, which allows callers to detect when
> deferred probe should occur.
...
...
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> +static inline struct dma_chan *dma_request_slave_channel_or_err(
> + struct device *dev, const char *name)
> +{
> + return ERR_PTR(-ENODEV);
> +}
That requires the following to be squashed into it, which I'll apply
locally:
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index b908b0fda72b..f156c145fad2 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -22,6 +22,7 @@
#define LINUX_DMAENGINE_H
#include <linux/device.h>
+#include <linux/err.h>
#include <linux/uio.h>
#include <linux/bug.h>
#include <linux/scatterlist.h>
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