On 04/22/2013 04:00 PM, Lars-Peter Clausen wrote:
> 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.
Thanks for the clarification. I should have looked more closely at
of_parse_phandle_with_args().
Yes I agree it will always be true if count is less than or equal to
MAX_PHANDLE_ARGS (which defaults to 8). It is very unlikely that someone
would use more than 8 and I guess it does warn on this condition.
if (out_args) {
int i;
if (WARN_ON(count > MAX_PHANDLE_ARGS))
count = MAX_PHANDLE_ARGS;
out_args->np = node;
out_args->args_count = count;
for (i = 0; i < count; i++)
out_args->args[i] = be32_to_cpup(list++);
}
Cheers
Jon
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
