On 09/11/2017 03:27 PM, Sakari Ailus wrote:
> Hi Hans,
>
> On Mon, Sep 11, 2017 at 02:38:23PM +0200, Hans Verkuil wrote:
>> On 09/11/2017 02:28 PM, Sakari Ailus wrote:
>>> Hi Hans,
>>>
>>> Thanks for the review.
>>>
>>> On Mon, Sep 11, 2017 at 11:38:58AM +0200, Hans Verkuil wrote:
>>>> Typo in subject: interger -> integer
>>>>
>>>> On 09/11/2017 10:00 AM, Sakari Ailus wrote:
>>>>> v4l2_fwnode_reference_parse_int_prop() will find an fwnode such that under
>>>>> the device's own fwnode,
>>>>
>>>> Sorry, you lost me here. Which device are we talking about?
>>>
>>> The fwnode related a struct device, in other words what dev_fwnode(dev)
>>> gives you. This is either struct device.fwnode or struct
>>> device.of_node.fwnode, depending on which firmware interface was used to
>>> create the device.
>>>
>>> I'll add a note of this.
>>>
>>>>
>>>>> it will follow child fwnodes with the given
>>>>> property -- value pair and return the resulting fwnode.
>>>>
>>>> property-value pair (easier readable that way).
>>>>
>>>> You only describe v4l2_fwnode_reference_parse_int_prop(), not
>>>> v4l2_fwnode_reference_parse_int_props().
>>>
>>> Yes, I think I changed the naming but forgot to update the commit. I'll do
>>> that now.
>>>
>>>>
>>>>>
>>>>> Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
>>>>> ---
>>>>> drivers/media/v4l2-core/v4l2-fwnode.c | 93 +++++++++++++++++++++++++++++++++++
>>>>> 1 file changed, 93 insertions(+)
>>>>>
>>>>> diff --git a/drivers/media/v4l2-core/v4l2-fwnode.c b/drivers/media/v4l2-core/v4l2-fwnode.c
>>>>> index 4821c4989119..56eee5bbd3b5 100644
>>>>> --- a/drivers/media/v4l2-core/v4l2-fwnode.c
>>>>> +++ b/drivers/media/v4l2-core/v4l2-fwnode.c
>>>>> @@ -496,6 +496,99 @@ static int v4l2_fwnode_reference_parse(
>>>>> return ret;
>>>>> }
>>>>>
>>>>> +static struct fwnode_handle *v4l2_fwnode_reference_get_int_prop(
>>>>> + struct fwnode_handle *fwnode, const char *prop, unsigned int index,
>>>>> + const char **props, unsigned int nprops)
>>>>
>>>> Need comments describing what this does.
>>>
>>> Yes. I'll also rename it (get -> read) for consistency with the async
>>> changes.
>>
>> Which async changes? Since the fwnode_handle that's returned is refcounted
>> I wonder if 'get' isn't the right name in this case.
>
> Right. True. I'll leave that as-is then.
>
>>
>>>
>>>>
>>>>> +{
>>>>> + struct fwnode_reference_args fwnode_args;
>>>>> + unsigned int *args = fwnode_args.args;
>>>>> + struct fwnode_handle *child;
>>>>> + int ret;
>>>>> +
>>>>> + ret = fwnode_property_get_reference_args(fwnode, prop, NULL, nprops,
>>>>> + index, &fwnode_args);
>>>>> + if (ret)
>>>>> + return ERR_PTR(ret == -EINVAL ? -ENOENT : ret);
>>>>
>>>> Why map EINVAL to ENOENT? Needs a comment, either here or in the function description.
>>>
>>> fwnode_property_get_reference_args() returns currently a little bit
>>> different error codes in ACPI / DT. This is worth documenting there and
>>> fixing as well.
>>>
>>>>
>>>>> +
>>>>> + for (fwnode = fwnode_args.fwnode;
>>>>> + nprops; nprops--, fwnode = child, props++, args++) {
>>>>
>>>> I think you cram too much in this for-loop: fwnode, nprops, fwnode, props, args...
>>>> It's hard to parse.
>>>
>>> Hmm. I'm not sure if that really helps; the function is just handling each
>>> entry in the array and related array pointers are changed accordingly. The
>>> fwnode = child assignment is there to move to the child node. I.e. what you
>>> need for handling the loop itself.
>>>
>>> I can change this though if you think it really makes a difference for
>>> better.
>>
>> I think so, yes. I noticed you like complex for-loops :-)
>
> I don't really see a difference. The loop increment will just move at the
> end of the block inside the loop.
>
>>
>>>
>>>>
>>>> I would make this a 'while (nprops)' and write out all the other assignments,
>>>> increments and decrements.
>>>>
>>>>> + u32 val;
>>>>> +
>>>>> + fwnode_for_each_child_node(fwnode, child) {
>>>>> + if (fwnode_property_read_u32(child, *props, &val))
>>>>> + continue;
>>>>> +
>>>>> + if (val == *args)
>>>>> + break;
>>>>
>>>> I'm lost. This really needs comments and perhaps even an DT or ACPI example
>>>> so you can see what exactly it is we're doing here.
>>>
>>> I'll add comments to the code. A good example will be ACPI documentation
>>> for LEDs, see 17th patch in v9. That will go through the linux-pm tree so
>>> it won't be available in the same tree for a while.
>>
>> Ideally an ACPI and an equivalent DT example would be nice to have, but I might
>> be asking too much. I'm not that familiar with ACPI, so for me a DT example
>> is easier.
>
> This won't be useful on DT although you could technically use it. In DT you
> can directly refer to any node but on ACPI you can just refer to devices,
> hence this.
So this function will effectively only be used with acpi? That should be
documented. I think that explains some of my confusion since I was trying
to map this code to a device tree, without much success.
> Would you be happy with the leds.txt example? I think it's a good example
> as it's directly related to this.
Yes, that will work.
Regards,
Hans
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