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.
>
> 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'?
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.
> + *
> + * 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.
> + *
> + * 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.
> + 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.
> + fwnode_for_each_child_node(fwnode, child) {
> + if (fwnode_property_read_u32(child, *props, &val))
> + continue;
> +
> + /* Found property, see if its value matches. */
> + if (val == *args)
> + break;
> + }
> +
> + fwnode_handle_put(fwnode);
> +
> + /* No property found; return an error here. */
> + if (!child) {
> + fwnode = ERR_PTR(-ENOENT);
> + break;
> + }
> +
> + props++;
> + args++;
> + fwnode = child;
> + }
> +
> + return fwnode;
> +}
> +
> +/*
> + * v4l2_fwnode_reference_parse_int_props - parse references for async sub-devices
> + * @dev: struct device pointer
> + * @notifier: notifier for @dev
> + * @prop: the name of the property
> + * @props: the array of integer property names
> + * @nprops: the number of integer properties
> + *
> + * Use v4l2_fwnode_reference_get_int_prop to find fwnodes through reference in
> + * property @prop with integer arguments with child nodes matching in properties
> + * @props. Then, set up V4L2 async sub-devices for those fwnodes in the notifier
> + * accordingly.
> + *
> + * While it is technically possible to use this function on DT, it is only
> + * meaningful on ACPI. On Device tree you can refer to any node in the tree but
> + * on ACPI the references are limited to devices.
> + *
> + * Return: 0 on success
> + * -ENOENT if no entries (or the property itself) were found
> + * -EINVAL if property parsing otherwisefailed
> + * -ENOMEM if memory allocation failed
> + */
> +static int v4l2_fwnode_reference_parse_int_props(
> + struct device *dev, struct v4l2_async_notifier *notifier,
> + const char *prop, const char **props, unsigned int nprops)
> +{
> + struct fwnode_handle *fwnode;
> + unsigned int index;
> + int ret;
> +
> + for (index = 0; !IS_ERR((fwnode = v4l2_fwnode_reference_get_int_prop(
> + dev_fwnode(dev), prop, index, props,
> + nprops))); index++)
> + fwnode_handle_put(fwnode);
> +
> + /*
> + * Note that right now both -ENODATA and -ENOENT may signal
> + * out-of-bounds access. Return the error in cases other than that.
> + */
> + if (PTR_ERR(fwnode) != -ENOENT && PTR_ERR(fwnode) != -ENODATA)
> + return PTR_ERR(fwnode);
> +
> + ret = v4l2_async_notifier_realloc(notifier,
> + notifier->num_subdevs + index);
> + if (ret)
> + return -ENOMEM;
> +
> + for (index = 0; !IS_ERR((fwnode = v4l2_fwnode_reference_get_int_prop(
> + dev_fwnode(dev), prop, index, props,
> + nprops))); index++) {
> + struct v4l2_async_subdev *asd;
> +
> + if (WARN_ON(notifier->num_subdevs >= notifier->max_subdevs)) {
> + ret = -EINVAL;
> + goto error;
> + }
> +
> + asd = kzalloc(sizeof(struct v4l2_async_subdev), GFP_KERNEL);
> + if (!asd) {
> + ret = -ENOMEM;
> + goto error;
> + }
> +
> + notifier->subdevs[notifier->num_subdevs] = asd;
> + asd->match.fwnode.fwnode = fwnode;
> + asd->match_type = V4L2_ASYNC_MATCH_FWNODE;
> + notifier->num_subdevs++;
> + }
> +
> + return PTR_ERR(fwnode) == -ENOENT ? 0 : PTR_ERR(fwnode);
> +
> +error:
> + fwnode_handle_put(fwnode);
> + return ret;
> +}
> +
> MODULE_LICENSE("GPL");
> MODULE_AUTHOR("Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>");
> MODULE_AUTHOR("Sylwester Nawrocki <s.nawrocki@xxxxxxxxxxx>");
>
Regards,
Hans
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