On 09/19/17 10:45, Sakari Ailus wrote:
> Hi Hans,
>
> Thank you for the review.
>
> On Tue, Sep 19, 2017 at 10:31:41AM +0200, Hans Verkuil wrote:
>> Hi Sakari,
>>
>> I'm slowly starting to understand this. The example helped a lot. But I still have
>> some questions, see below.
>>
>> On 09/15/2017 04:17 PM, Sakari Ailus wrote:
>>> v4l2_fwnode_reference_parse_int_prop() will find an fwnode such that under
>>> the device's own fwnode, it will follow child fwnodes with the given
>>> property-value pair and return the resulting fwnode.
>>
>> I think both the subject, commit log, function comment and function name should
>> reflect the fact that this function is for an ACPI reference.
>>
>> It's only called for ACPI (from patch 19):
>>
>> + if (props[i].props && is_acpi_node(dev_fwnode(dev)))
>> + ret = v4l2_fwnode_reference_parse_int_props(
>>
>> So renaming it to v4l2_fwnode_acpi_reference_parse_int_props or something similar
>> would clarify this fact.
>
> I don't think we'll see many like this one. I presume we won't use it on DT
> albeit there are no direct references to ACPI in the code itself.
>
> How about v4l2_fwnode_parse_acpi_reference (+ "s" for the one below)?
Sounds good.
>
>>
>>>
>>> Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
>>> ---
>>> drivers/media/v4l2-core/v4l2-fwnode.c | 201 ++++++++++++++++++++++++++++++++++
>>> 1 file changed, 201 insertions(+)
>>>
>>> diff --git a/drivers/media/v4l2-core/v4l2-fwnode.c b/drivers/media/v4l2-core/v4l2-fwnode.c
>>> index 65e84ea1cc35..968a345a288f 100644
>>> --- a/drivers/media/v4l2-core/v4l2-fwnode.c
>>> +++ b/drivers/media/v4l2-core/v4l2-fwnode.c
>>> @@ -567,6 +567,207 @@ static int v4l2_fwnode_reference_parse(
>>> return ret;
>>> }
>>>
>>> +/*
>>> + * v4l2_fwnode_reference_get_int_prop - parse a reference with integer
>>> + * arguments
>>> + * @dev: struct device pointer
>>> + * @notifier: notifier for @dev
>>> + * @prop: the name of the property
>>> + * @index: the index of the reference to get
>>> + * @props: the array of integer property names
>>> + * @nprops: the number of integer property names in @nprops
>>
>> You mean 'in @props'?
>
> Yes, I'll fix that.
>
>>
>> One thing that is not clear to me is when you would use an nprops value > 1.
>> What's the use-case for that? It only makes sense (I think) if you would have
>> property names that are all aliases of one another.
>
> There may be several flash LEDs related to a sensor. That's the use case,
> for instance.
I think it would be helpful if the example shows two LEDs related to a
sensor. Part of the problem I have in understanding this code is that I
have zero experience with ACPI (and that is probably true for most other
developers), so I don't know how this is encoded. With a good example it
is much easier to understand.
>
>>
>>> + *
>>> + * Find fwnodes referred to by a property @prop, then under that
>>> + * iteratively, @nprops times, follow each child node which has a
>>> + * property in @props array at a given child index the value of which
>>> + * matches the integer argument at an index.
>>> + *
>>> + * For example, if this function was called with arguments and values
>>> + * @dev corresponding to device "SEN", @prop == "flash-leds", @index
>>> + * == 1, @props == { "led" }, @nprops == 1, with the ASL snippet below
>>> + * it would return the node marked with THISONE. The @dev argument in
>>> + * the ASL below.
>>
>> That last sentence about the @dev seems incomplete. I'm not sure what is
>> meant by it.
>
> I think it was meant to convey some information but it got added to the
> previous sentence. I'll remove it.
>
>>
>>> + *
>>> + * Device (LED)
>>> + * {
>>> + * Name (_DSD, Package () {
>>> + * ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"),
>>> + * Package () {
>>> + * Package () { "led0", "LED0" },
>>> + * Package () { "led1", "LED1" },
>>> + * }
>>> + * })
>>> + * Name (LED0, Package () {
>>> + * ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
>>> + * Package () {
>>> + * Package () { "led", 0 },
>>> + * }
>>> + * })
>>> + * Name (LED1, Package () {
>>> + * // THISONE
>>> + * ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
>>> + * Package () {
>>> + * Package () { "led", 1 },
>>> + * }
>>> + * })
>>> + * }
>>> + *
>>> + * Device (SEN)
>>> + * {
>>> + * Name (_DSD, Package () {
>>> + * ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
>>> + * Package () {
>>> + * Package () {
>>> + * "flash-leds",
>>> + * Package () { ^LED, 0, ^LED, 1 },
>>> + * }
>>> + * }
>>> + * })
>>> + * }
>>> + *
>>> + * where
>>> + *
>>> + * LED LED driver device
>>> + * LED0 First LED
>>> + * LED1 Second LED
>>> + * SEN Camera sensor device (or another device the LED is
>>> + * related to)
>>> + *
>>> + * Return: 0 on success
>>> + * -ENOENT if no entries (or the property itself) were found
>>> + * -EINVAL if property parsing otherwise failed
>>> + * -ENOMEM if memory allocation failed
>>> + */
>>> +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)
>>> +{
>>> + struct fwnode_reference_args fwnode_args;
>>> + unsigned int *args = fwnode_args.args;
>>> + struct fwnode_handle *child;
>>> + int ret;
>>> +
>>> + /*
>>> + * Obtain remote fwnode as well as the integer arguments.
>>> + *
>>> + * Note that right now both -ENODATA and -ENOENT may signal
>>> + * out-of-bounds access. Return -ENOENT in that case.
>>> + */
>>> + ret = fwnode_property_get_reference_args(fwnode, prop, NULL, nprops,
>>> + index, &fwnode_args);
>>> + if (ret)
>>> + return ERR_PTR(ret == -ENODATA ? -ENOENT : ret);
>>> +
>>> + /*
>>> + * Find a node in the tree under the referred fwnode corresponding the
>>> + * integer arguments.
>>> + */
>>> + fwnode = fwnode_args.fwnode;
>>
>> So given the example above, fwnode would point to the LED device?
>>
>> If correct, then mention that in the comment.
>
> It could be a LED driver device, but it could be something else as well.
> Like a lens VCM, depending on the property being parsed. That's why I
> didn't put it in the comments. But this is a device node, not a
> hierarchical data extension node, for instance. That's what I think I
> should add.
I think that will help.
>
>>
>>> + while (nprops--) {
>>> + u32 val;
>>> +
>>> + /* Loop over all child nodes under fwnode. */
>>
>> And here you check if the LED device has child nodes that have a *props
>> property with a value matching the index.
>>
>> So given the example above it is looking for a child with property "led"
>> and value 1.
>>
>> It's useful if that is mentioned in the comment as well.
>
> But should I? This isn't specific to LEDs.
Ignore this comment for now. I'll take another look when I see v14.
Regards,
Hans
