Re: [PATCH v8 06/21] v4l: fwnode: Support generic parsing of graph endpoints in a device

[Hans Verkuil <hverkuil-qWit8jRvyhVmR6Xm/wNWPw@public.gmane.org>]

On 09/05/2017 03:05 PM, Sakari Ailus wrote:
> The current practice is that drivers iterate over their endpoints and
> parse each endpoint separately. This is very similar in a number of
> drivers, implement a generic function for the job. Driver specific matters
> can be taken into account in the driver specific callback.
> 
> Signed-off-by: Sakari Ailus <sakari.ailus-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> ---
>  drivers/media/v4l2-core/v4l2-async.c  |  19 +++++
>  drivers/media/v4l2-core/v4l2-fwnode.c | 140 ++++++++++++++++++++++++++++++++++
>  include/media/v4l2-async.h            |  24 +++++-
>  include/media/v4l2-fwnode.h           |  53 +++++++++++++
>  4 files changed, 234 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-async.c b/drivers/media/v4l2-core/v4l2-async.c
> index 3d81ff6a496f..7bd595c4094a 100644
> --- a/drivers/media/v4l2-core/v4l2-async.c
> +++ b/drivers/media/v4l2-core/v4l2-async.c
> @@ -22,6 +22,7 @@
>  
>  #include <media/v4l2-async.h>
>  #include <media/v4l2-device.h>
> +#include <media/v4l2-fwnode.h>
>  #include <media/v4l2-subdev.h>
>  
>  static bool match_i2c(struct v4l2_subdev *sd, struct v4l2_async_subdev *asd)
> @@ -224,6 +225,24 @@ void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier)
>  }
>  EXPORT_SYMBOL(v4l2_async_notifier_unregister);
>  
> +void v4l2_async_notifier_release(struct v4l2_async_notifier *notifier)
> +{
> +	unsigned int i;
> +
> +	if (!notifier->max_subdevs)
> +		return;
> +
> +	for (i = 0; i < notifier->num_subdevs; i++)
> +		kfree(notifier->subdevs[i]);
> +
> +	notifier->max_subdevs = 0;
> +	notifier->num_subdevs = 0;
> +
> +	kvfree(notifier->subdevs);
> +	notifier->subdevs = NULL;
> +}
> +EXPORT_SYMBOL_GPL(v4l2_async_notifier_release);
> +
>  int v4l2_async_register_subdev(struct v4l2_subdev *sd)
>  {
>  	struct v4l2_async_notifier *notifier;
> diff --git a/drivers/media/v4l2-core/v4l2-fwnode.c b/drivers/media/v4l2-core/v4l2-fwnode.c
> index 706f9e7b90f1..e6932d7d47b6 100644
> --- a/drivers/media/v4l2-core/v4l2-fwnode.c
> +++ b/drivers/media/v4l2-core/v4l2-fwnode.c
> @@ -19,6 +19,7 @@
>   */
>  #include <linux/acpi.h>
>  #include <linux/kernel.h>
> +#include <linux/mm.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
>  #include <linux/property.h>
> @@ -26,6 +27,7 @@
>  #include <linux/string.h>
>  #include <linux/types.h>
>  
> +#include <media/v4l2-async.h>
>  #include <media/v4l2-fwnode.h>
>  
>  enum v4l2_fwnode_bus_type {
> @@ -313,6 +315,144 @@ void v4l2_fwnode_put_link(struct v4l2_fwnode_link *link)
>  }
>  EXPORT_SYMBOL_GPL(v4l2_fwnode_put_link);
>  
> +static int v4l2_async_notifier_realloc(struct v4l2_async_notifier *notifier,
> +				       unsigned int max_subdevs)
> +{
> +	struct v4l2_async_subdev **subdevs;
> +
> +	if (max_subdevs <= notifier->max_subdevs)
> +		return 0;
> +
> +	subdevs = kvmalloc_array(
> +		max_subdevs, sizeof(*notifier->subdevs),
> +		GFP_KERNEL | __GFP_ZERO);
> +	if (!subdevs)
> +		return -ENOMEM;
> +
> +	if (notifier->subdevs) {
> +		memcpy(subdevs, notifier->subdevs,
> +		       sizeof(*subdevs) * notifier->num_subdevs);
> +
> +		kvfree(notifier->subdevs);
> +	}
> +
> +	notifier->subdevs = subdevs;
> +	notifier->max_subdevs = max_subdevs;
> +
> +	return 0;
> +}
> +
> +static int v4l2_async_notifier_fwnode_parse_endpoint(
> +	struct device *dev, struct v4l2_async_notifier *notifier,
> +	struct fwnode_handle *endpoint, unsigned int asd_struct_size,
> +	int (*parse_endpoint)(struct device *dev,
> +			    struct v4l2_fwnode_endpoint *vep,
> +			    struct v4l2_async_subdev *asd))
> +{
> +	struct v4l2_async_subdev *asd;
> +	struct v4l2_fwnode_endpoint *vep;
> +	struct fwnode_endpoint ep;
> +	int ret = 0;
> +
> +	asd = kzalloc(asd_struct_size, GFP_KERNEL);
> +	if (!asd)
> +		return -ENOMEM;
> +
> +	asd->match.fwnode.fwnode =
> +		fwnode_graph_get_remote_port_parent(endpoint);
> +	if (!asd->match.fwnode.fwnode) {
> +		dev_warn(dev, "bad remote port parent\n");
> +		ret = -EINVAL;
> +		goto out_err;
> +	}
> +
> +	/* Ignore endpoints the parsing of which failed. */
> +	vep = v4l2_fwnode_endpoint_alloc_parse(endpoint);
> +	if (IS_ERR(vep)) {
> +		ret = PTR_ERR(vep);
> +		dev_warn(dev, "unable to parse V4L2 fwnode endpoint (%d)\n",
> +			 ret);
> +		goto out_err;
> +	}
> +
> +	ep = vep->base;
> +
> +	ret = parse_endpoint ? parse_endpoint(dev, vep, asd) : 0;
> +	v4l2_fwnode_endpoint_free(vep);
> +	if (ret == -ENOTCONN) {
> +		dev_dbg(dev, "ignoring endpoint %u,%u\n", ep.port, ep.id);
> +		kfree(asd);

Shouldn't there be a call to fwnode_handle_put()?

> +		return 0;
> +	} else if (ret < 0) {
> +		dev_warn(dev, "driver could not parse endpoint %u,%u (%d)\n",
> +			 ep.port, ep.id, ret);
> +		goto out_err;
> +	}

I think this would be better and it avoids the need for the ep local variable:

	ret = parse_endpoint ? parse_endpoint(dev, vep, asd) : 0;
	if (ret == -ENOTCONN)
		dev_dbg(dev, "ignoring endpoint %u,%u\n", vep->base.port, vep->base.id);
	else if (ret < 0)
		dev_warn(dev, "driver could not parse endpoint %u,%u (%d)\n",
			 vep->base.port, vep->base.id, ret);
	v4l2_fwnode_endpoint_free(vep);
	if (ret < 0)
		goto out_err;

And the 'return ret;' below would become:

	return ret == -ENOTCONN ? 0 : ret;

> +
> +	asd->match_type = V4L2_ASYNC_MATCH_FWNODE;
> +	notifier->subdevs[notifier->num_subdevs] = asd;
> +	notifier->num_subdevs++;
> +
> +	return 0;
> +
> +out_err:
> +	fwnode_handle_put(asd->match.fwnode.fwnode);
> +	kfree(asd);
> +
> +	return ret;
> +}
> +
> +int v4l2_async_notifier_parse_fwnode_endpoints(
> +	struct device *dev, struct v4l2_async_notifier *notifier,
> +	size_t asd_struct_size,
> +	int (*parse_endpoint)(struct device *dev,
> +			    struct v4l2_fwnode_endpoint *vep,
> +			    struct v4l2_async_subdev *asd))
> +{
> +	struct fwnode_handle *fwnode = NULL;
> +	unsigned int max_subdevs = notifier->max_subdevs;
> +	int ret;
> +
> +	if (asd_struct_size < sizeof(struct v4l2_async_subdev))

I think this can be a WARN_ON or a WARN_ON_ONCE. Up to you, though.

> +		return -EINVAL;
> +
> +	for (fwnode = NULL; (fwnode = fwnode_graph_get_next_endpoint(
> +				     dev_fwnode(dev), fwnode)); )
> +		if (fwnode_device_is_available(
> +			    fwnode_graph_get_port_parent(fwnode)))
> +			max_subdevs++;

I think I would prefer this as a simple for (;;):

	for (;;) {
		fwnode = fwnode_graph_get_next_endpoint(dev_fwnode(dev), fwnode));
		if (fwnode == NULL)
			break;
		...
	}

Or alternatively as a do...while:

	do {
		fwnode = fwnode_graph_get_next_endpoint(dev_fwnode(dev), fwnode));
		if (fwnode && fwnode_device_is_available(
			    fwnode_graph_get_port_parent(fwnode)))
			max_subdevs++;
	} while (fwnode);

Both are IMHO a bit more readable. I leave it up to you, though.

> +
> +	/* No subdevs to add? Return here. */
> +	if (max_subdevs == notifier->max_subdevs)
> +		return 0;
> +
> +	ret = v4l2_async_notifier_realloc(notifier, max_subdevs);
> +	if (ret)
> +		return ret;
> +
> +	for (fwnode = NULL; (fwnode = fwnode_graph_get_next_endpoint(
> +				     dev_fwnode(dev), fwnode)); ) {

Same comment as above.

> +		if (!fwnode_device_is_available(
> +			    fwnode_graph_get_port_parent(fwnode)))
> +			continue;
> +
> +		if (WARN_ON(notifier->num_subdevs >= notifier->max_subdevs)) {
> +			ret = -EINVAL;
> +			break;
> +		}
> +
> +		ret = v4l2_async_notifier_fwnode_parse_endpoint(
> +			dev, notifier, fwnode, asd_struct_size, parse_endpoint);
> +		if (ret < 0)
> +			break;
> +	}
> +
> +	fwnode_handle_put(fwnode);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(v4l2_async_notifier_parse_fwnode_endpoints);
> +
>  MODULE_LICENSE("GPL");
>  MODULE_AUTHOR("Sakari Ailus <sakari.ailus-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>");
>  MODULE_AUTHOR("Sylwester Nawrocki <s.nawrocki-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>");
> diff --git a/include/media/v4l2-async.h b/include/media/v4l2-async.h
> index c69d8c8a66d0..96fa1afc00dd 100644
> --- a/include/media/v4l2-async.h
> +++ b/include/media/v4l2-async.h
> @@ -18,7 +18,6 @@ struct device;
>  struct device_node;
>  struct v4l2_device;
>  struct v4l2_subdev;
> -struct v4l2_async_notifier;
>  
>  /* A random max subdevice number, used to allocate an array on stack */
>  #define V4L2_MAX_SUBDEVS 128U
> @@ -50,6 +49,10 @@ enum v4l2_async_match_type {
>   * @match:	union of per-bus type matching data sets
>   * @list:	used to link struct v4l2_async_subdev objects, waiting to be
>   *		probed, to a notifier->waiting list
> + *
> + * When this struct is used as a member in a driver specific struct,
> + * the driver specific struct shall contain the @struct
> + * v4l2_async_subdev as its first member.
>   */
>  struct v4l2_async_subdev {
>  	enum v4l2_async_match_type match_type;
> @@ -78,7 +81,8 @@ struct v4l2_async_subdev {
>  /**
>   * struct v4l2_async_notifier - v4l2_device notifier data
>   *
> - * @num_subdevs: number of subdevices
> + * @num_subdevs: number of subdevices used in the subdevs array
> + * @max_subdevs: number of subdevices allocated in the subdevs array
>   * @subdevs:	array of pointers to subdevice descriptors
>   * @v4l2_dev:	pointer to struct v4l2_device
>   * @waiting:	list of struct v4l2_async_subdev, waiting for their drivers
> @@ -90,6 +94,7 @@ struct v4l2_async_subdev {
>   */
>  struct v4l2_async_notifier {
>  	unsigned int num_subdevs;
> +	unsigned int max_subdevs;
>  	struct v4l2_async_subdev **subdevs;
>  	struct v4l2_device *v4l2_dev;
>  	struct list_head waiting;
> @@ -121,6 +126,21 @@ int v4l2_async_notifier_register(struct v4l2_device *v4l2_dev,
>  void v4l2_async_notifier_unregister(struct v4l2_async_notifier *notifier);
>  
>  /**
> + * v4l2_async_notifier_release - release notifier resources
> + * @notifier: the notifier the resources of which are to be released
> + *
> + * Release memory resources related to a notifier, including the async
> + * sub-devices allocated for the purposes of the notifier. The user is
> + * responsible for releasing the notifier's resources after calling
> + * @v4l2_async_notifier_parse_fwnode_endpoints.
> + *
> + * There is no harm from calling v4l2_async_notifier_release in other
> + * cases as long as its memory has been zeroed after it has been
> + * allocated.
> + */
> +void v4l2_async_notifier_release(struct v4l2_async_notifier *notifier);
> +
> +/**
>   * v4l2_async_register_subdev - registers a sub-device to the asynchronous
>   * 	subdevice framework
>   *
> diff --git a/include/media/v4l2-fwnode.h b/include/media/v4l2-fwnode.h
> index 68eb22ba571b..6d125f26ec84 100644
> --- a/include/media/v4l2-fwnode.h
> +++ b/include/media/v4l2-fwnode.h
> @@ -25,6 +25,8 @@
>  #include <media/v4l2-mediabus.h>
>  
>  struct fwnode_handle;
> +struct v4l2_async_notifier;
> +struct v4l2_async_subdev;
>  
>  #define V4L2_FWNODE_CSI2_MAX_DATA_LANES	4
>  
> @@ -201,4 +203,55 @@ int v4l2_fwnode_parse_link(struct fwnode_handle *fwnode,
>   */
>  void v4l2_fwnode_put_link(struct v4l2_fwnode_link *link);
>  
> +/**
> + * v4l2_async_notifier_parse_fwnode_endpoints - Parse V4L2 fwnode endpoints in a
> + *						device node
> + * @dev: the device the endpoints of which are to be parsed
> + * @notifier: notifier for @dev
> + * @asd_struct_size: size of the driver's async sub-device struct, including
> + *		     sizeof(struct v4l2_async_subdev). The &struct
> + *		     v4l2_async_subdev shall be the first member of
> + *		     the driver's async sub-device struct, i.e. both
> + *		     begin at the same memory address.
> + * @parse_endpoint: Driver's callback function called on each V4L2 fwnode
> + *		    endpoint. Optional.
> + *		    Return: %0 on success
> + *			    %-ENOTCONN if the endpoint is to be skipped but this
> + *				       should not be considered as an error
> + *			    %-EINVAL if the endpoint configuration is invalid
> + *
> + * Parse the fwnode endpoints of the @dev device and populate the async sub-
> + * devices array of the notifier. The @parse_endpoint callback function is
> + * called for each endpoint with the corresponding async sub-device pointer to
> + * let the caller initialize the driver-specific part of the async sub-device
> + * structure.
> + *
> + * The notifier memory shall be zeroed before this function is called on the
> + * notifier.
> + *
> + * This function may not be called on a registered notifier and may be called on
> + * a notifier only once. When using this function, the user may not access the
> + * notifier's subdevs array nor change notifier's num_subdevs field, these are
> + * reserved for the framework's internal use only.

The rvin_digital_graph_init() function accesses the subdevs array.

I still don't like this sentence, and I still think it should be dropped. Either that
or completely rewritten.

> + *
> + * The @struct v4l2_fwnode_endpoint passed to the callback function
> + * @parse_endpoint is released once the function is finished. If there is a need
> + * to retain that configuration, the user needs to allocate memory for it.
> + *
> + * Any notifier populated using this function must be released with a call to
> + * v4l2_async_notifier_release() after it has been unregistered and the async
> + * sub-devices are no longer in use.
> + *
> + * Return: %0 on success, including when no async sub-devices are found
> + *	   %-ENOMEM if memory allocation failed
> + *	   %-EINVAL if graph or endpoint parsing failed
> + *	   Other error codes as returned by @parse_endpoint
> + */
> +int v4l2_async_notifier_parse_fwnode_endpoints(
> +	struct device *dev, struct v4l2_async_notifier *notifier,
> +	size_t asd_struct_size,
> +	int (*parse_endpoint)(struct device *dev,
> +			      struct v4l2_fwnode_endpoint *vep,
> +			      struct v4l2_async_subdev *asd));
> +
>  #endif /* _V4L2_FWNODE_H */
> 

Regards,

	Hans
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