Re: [PATCH v5 07/14] dmaengine: add dma_request_slave_channel_compat()

Arnd Bergmann
2013-01-23T22:29:40Z

On Tuesday 15 January 2013, Matt Porter wrote:
> Adds a dma_request_slave_channel_compat() wrapper which accepts
> both the arguments from dma_request_channel() and
> dma_request_slave_channel(). Based on whether the driver is
> instantiated via DT, the appropriate channel request call will be
> made.
>
> This allows for a much cleaner migration of drivers to the
> dmaengine DT API as platforms continue to be mixed between those
> that boot using DT and those that do not.

I noticed today some drivers in linux-next that rely on this patch,
but the patch itself still missing from -next.

> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -1047,6 +1047,16 @@ void dma_run_dependencies(struct dma_async_tx_descriptor *tx);
> struct dma_chan *dma_find_channel(enum dma_transaction_type tx_type);
> struct dma_chan *net_dma_find_channel(void);
> #define dma_request_channel(mask, x, y) __dma_request_channel(&(mask), x, y)
> +static inline struct dma_chan
> +*dma_request_slave_channel_compat(dma_cap_mask_t mask, dma_filter_fn fn,
> + void *fn_param, struct device *dev,
> + char *name)
> +{
> + if (dev->of_node)
> + return dma_request_slave_channel(dev, name);
> + else
> + return dma_request_channel(mask, fn, fn_param);
> +}

Hmm, dma_request_channel is actually a macro that passes mask by reference,
presumably because it can get modified by the filter function. Also, there
may be cases where we do have an of_node but don't use the dma binding
yet, or where dma_request_slave_channel doesn't actually use DT information
but rather one of the other methods that Vinod was talking about adding.

I think what it should look like instead is the below.

Arnd

diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index bfcdecb..b6ffd7d 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -993,6 +993,19 @@ static inline void dma_release_channel(struct dma_chan *chan)
}
#endif

+static inline struct dma_chan *__dma_request_slave_channel_compat(dma_cap_mask_t *mask,
+ dma_filter_fn fn, void *fn_param, struct device *dev,
+ char *name)
+{
+ struct dma_chan *chan;
+
+ chan = dma_request_slave_channel(dev, name);
+ if (chan)
+ return chan;
+
+ return __dma_request_channel(mask, fn, fn_param);
+}
+
/* --- DMA device --- */

int dma_async_device_register(struct dma_device *device);
@@ -1001,6 +1014,8 @@ void dma_run_dependencies(struct dma_async_tx_descriptor *tx);
struct dma_chan *dma_find_channel(enum dma_transaction_type tx_type);
struct dma_chan *net_dma_find_channel(void);
#define dma_request_channel(mask, x, y) __dma_request_channel(&(mask), x, y)
+#define dma_request_slave_channel_compat(mask, x, y, dev, name) \
+ __dma_request_slave_channel_compat(&(mask), x, y, dev, name)

/* --- Helper iov-locking functions --- */