On Friday 22 March 2013, Andy Shevchenko wrote:
> There is no reason to build custom filter function and translation function
> inside the driver in case we have no DT platform.
> 
> This patch introduces new method dw_dma_of_controller_register() and moves all
> DT related stuff under #ifdef CONFIG_OF. It also helps to distinguish the real
> -ENODEV return code of fake one when of_dma_controller_register is not
> implemented.
> 
> Signed-off-by: Andy Shevchenko <[email protected]>

This should have no impact on the object code at all, since everything
inside of the #ifdef is be dropped by the compiler anyway if
of_dma_controller_register is stubbed out.

I generally prefer to have all driver code be compiled  all the time
to catch build regressions independent of the configuration, and leave
the #ifdefs in header files that provide the interfaces.

> -     if (pdev->dev.of_node) {
> -             err = of_dma_controller_register(pdev->dev.of_node,
> -                                              dw_dma_of_xlate, dw);
> -             if (err && err != -ENODEV)
> -                     dev_err(&pdev->dev,
> -                             "could not register of_dma_controller\n");
> -     }
> +     if (pdev->dev.of_node)
> +             dw_dma_of_controller_register(dw);

If you want to remove the "err != -ENODEV" check here, we could rewrite
this as 

        if (IS_ENABLED(CONFIG_OF)) && pdev->dev.of_node) {
                err = of_dma_controller_register(pdev->dev.of_node,
                                                 dw_dma_of_xlate, dw);
                if (err)
                        dev_err(&pdev->dev,
                                "could not register of_dma_controller\n");
        }

Or alternatively, we can change the of_dma_controller_register() stub to
return 0 if CONFIG_OF is disabled. That would also take care of similar
code in other dma engine drivers.

        Arnd
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