On 04/22/2013 10:52 PM, Jon Hunter wrote:
>
> On 04/22/2013 03:33 AM, Lars-Peter Clausen wrote:
>> Both of_dma_nbcells field of the of_dma_controller and the args_count field
>> of
>> the dma_spec are initialized by parsing the #dma-cells attribute of their
>> device
>> tree node. So if the device tree nodes of a DMA controller and the dma_spec
>> match this means that of_dma_nbcells and args_count will also match. So the
>> second test in the of_dma_find_controller loop is redundant because given the
>> first test yields true the second test will also yield true. So we can safely
>> remove the test whether of_dma_nbcells matches args_count. Since this was the
>> last user of the of_dma_nbcells field we can remove it altogether.
>
> This assumes that someone has correctly added the dma information to the
> dma slave binding. I could see systems where different dma controllers
> have different of_dma_nbcells and so someone could put the enter wrong
> number of cells for a dma slave binding. Its really to catch user error.
No, this assumes nothing. The condition will _always_ be true.
dma_spec->args_count is initialized by parsing the #dma-cells attribute of
dma_sepc->np. of_dma->of_dma_nbcells is initialized by parsing the #dma-cells
attribute of of_dma->of_node. If ofdma->of_node equals dma_spec->np then
dma_spec->args_count will also equal of_dma->of_dma_nbcells.
>
>> Signed-off-by: Lars-Peter Clausen <l...@metafoo.de>
>> ---
>> drivers/dma/of-dma.c | 14 +-------------
>> include/linux/of_dma.h | 1 -
>> 2 files changed, 1 insertion(+), 14 deletions(-)
>>
>> diff --git a/drivers/dma/of-dma.c b/drivers/dma/of-dma.c
>> index 268cc8a..75334bd 100644
>> --- a/drivers/dma/of-dma.c
>> +++ b/drivers/dma/of-dma.c
>> @@ -35,8 +35,7 @@ static struct of_dma *of_dma_find_controller(struct
>> of_phandle_args *dma_spec)
>> struct of_dma *ofdma;
>>
>> list_for_each_entry(ofdma, &of_dma_list, of_dma_controllers)
>> - if ((ofdma->of_node == dma_spec->np) &&
>> - (ofdma->of_dma_nbcells == dma_spec->args_count))
>> + if (ofdma->of_node == dma_spec->np)
>> return ofdma;
>
> Other device-tree functions perform similar tests to this such as ...
>
So it's redundant there as well ;)
> static int of_gpiochip_find_and_xlate(struct gpio_chip *gc, void *data)
> {
> struct gg_data *gg_data = data;
> int ret;
>
> if ((gc->of_node != gg_data->gpiospec.np) ||
> (gc->of_gpio_n_cells != gg_data->gpiospec.args_count) ||
> (!gc->of_xlate))
> return false;
>
> ...
>
> Cheers
> Jon
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