On Fri, Aug 23, 2013 at 04:36:53AM +0800, Stephen Warren wrote:
> On 08/22/2013 12:43 AM, Richard Zhao wrote:
> > DMA client device driver usually needs to know at probe time whether
> > dma controller has been registered to deffer probe. So add a help
> > function of_dma_check_controller.
> >
> > DMA request channel functions can also used to check it, but they
> > are usually called at open() time.
>
> This new function is almost identical to the existing
> of_dma_request_slave_channel(). Surely the code should be shared?
ofdma->of_dma_xlate(&dma_spec, ofdma);
The above is called holding of_dma_lock. If I want to abstract the
common lines, there' two options.
Option 1:
static struct of_dma* of_dma_check_controller_locked(np, name)
{
parameter check
get dma-names count and check return value
for loop to get of_dma
return PTR_ERR(err) or of_dma
}
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
const char *name)
{
chan = null;
mutex_lock(&of_dma_lock);
of_dma = of_dma_check_controller_locked(np, name)
if(!IS_ERR(of_dma))
chan = ofdma->of_dma_xlate(&dma_spec, ofdma);
mutex_unlock(&of_dma_lock);
return chan;
}
int of_dma_check_controller(struct device *dev, const char *name)
{
mutex_lock(&of_dma_lock);
ofdma = of_dma_check_controller_locked(dev->of_node, name);
mutex_unlock(&of_dma_lock);
if (IS_ERR(ofdma))
return ERR_PTR(ofdma);
else
return 0;
}
Option 2:
static struct of_dma* of_dma_check_controller_getlock(np, name)
{
parameter check
get dma-names count and check return value
for loop to get of_dma, get lock at old place
if failed, unlock.
return PTR_ERR(err) or of_dma
}
struct dma_chan *of_dma_request_slave_channel(struct device_node *np,
const char *name)
{
} of_dma = of_dma_check_controller_getlock(np, name)
if(!IS_ERR(of_dma)) {
chan = ofdma->of_dma_xlate(&dma_spec, ofdma);
unlock;
}
return chan;
}
int of_dma_check_controller(struct device *dev, const char *name)
ofdma = of_dma_check_controller_locked(dev->of_node, name);
if (IS_ERR(ofdma)) {
return ERR_PTR(ofdma);
} else {
unlock;
return 0;
}
}
> But that said, I don't see any need for a new function; why can't
> drivers simply call of_dma_request_slave_channel() at probe time;
It'll mislead user. channel supposed to be request at open time.
> from
> what I can see, that function doesn't actually request the channel, but
> rather simply looks it up, just like this one. The only difference is
> that of_dma_xlate() is also called, but that's just doing some data
> transformation, not actually recording channel ownership.
xlate function request the channel if things go well.
Thanks
Richard
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