[v4,12/30] libpdbg: Create virtual nodes based on system-path property

To create a virtual node, "system-path" property is used to denote the
attachment point in the system device tree view.

It's also possible to create virtual nodes from backend device tree as
nodes without compatible property.

If a virtual node is mapped to a real node, then copy any properties
(except #address-cells and #size-cells) to the real node.

Signed-off-by: Amitay Isaacs <amitay@ozlabs.org>
---
 libpdbg/device.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 97 insertions(+)

Reviewed-by: Alistair Popple <alistair@popple.id.au>

On Thursday, 3 October 2019 2:18:51 PM AEDT Amitay Isaacs wrote:
> To create a virtual node, "system-path" property is used to denote the
> attachment point in the system device tree view.
> 
> It's also possible to create virtual nodes from backend device tree as
> nodes without compatible property.
> 
> If a virtual node is mapped to a real node, then copy any properties
> (except #address-cells and #size-cells) to the real node.
> 
> Signed-off-by: Amitay Isaacs <amitay@ozlabs.org>
> ---
>  libpdbg/device.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 97 insertions(+)
> 
> diff --git a/libpdbg/device.c b/libpdbg/device.c
> index 2f3d677..d7cd980 100644
> --- a/libpdbg/device.c
> +++ b/libpdbg/device.c
> @@ -651,6 +651,102 @@ uint64_t pdbg_target_address(struct pdbg_target *target, uint64_t *out_size)
>  	return dt_get_number(p->prop, na);
>  }
>  
> +static struct pdbg_target *dt_new_virtual(struct pdbg_target *root, const char *system_path)
> +{
> +	char *parent_path, *sep;
> +	struct pdbg_target *parent, *vnode;
> +
> +	parent_path = strdup(system_path);
> +	assert(parent_path);
> +
> +	sep = strrchr(parent_path, '/');
> +	if (!sep || sep[1] == '\0') {
> +		PR_ERROR("Invalid path reference \"%s\"\n", system_path);
> +		free(parent_path);
> +		return NULL;
> +	}
> +
> +	*sep = '\0';
> +
> +	parent = dt_find_by_path(root, parent_path);
> +	if (!parent) {
> +		PR_ERROR("Invalid path reference \"%s\"\n", system_path);
> +		free(parent_path);
> +		return NULL;
> +	}
> +
> +	vnode = dt_new_node(sep+1, NULL, 0);
> +	assert(vnode);
> +
> +	free(parent_path);
> +
> +	if (!dt_attach_node(parent, vnode)) {
> +		free(vnode);
> +		return NULL;
> +	}
> +
> +	PR_DEBUG("Created virtual node %s\n", system_path);
> +	return vnode;
> +}
> +
> +static void dt_link_virtual(struct pdbg_target *node, struct pdbg_target *vnode)
> +{
> +	struct dt_property *prop = NULL, *next;
> +
> +	node->vnode = vnode;
> +	vnode->vnode = node;
> +
> +	/* Move any properties on virtual node to real node */
> +	list_for_each_safe(&vnode->properties, prop, next, list) {
> +		if (!strcmp(prop->name, "#address-cells") || !strcmp(prop->name, "#size-cells"))
> +			continue;
> +
> +		list_del(&prop->list);
> +		list_add_tail(&node->properties, &prop->list);
> +	}
> +}
> +
> +static void pdbg_targets_init_virtual(struct pdbg_target *node, struct pdbg_target *root)
> +{
> +	struct pdbg_target *vnode, *child = NULL;
> +	const char *system_path;
> +	size_t len;
> +
> +	system_path = (const char *)pdbg_target_property(node, "system-path", &len);
> +	if (!system_path)
> +		goto skip;
> +
> +	/*
> +	 * A virtual node identifies the attachment point of a node in the
> +	 * system tree.
> +	 */
> +	vnode = dt_find_by_path(root, system_path);
> +	if (!vnode)
> +		vnode = dt_new_virtual(root, system_path);
> +
> +	/* If virtual node does not exist, or cannot be created, skip */
> +	if (!vnode)
> +		goto skip;
> +
> +	assert(target_is_virtual(vnode));
> +
> +	/*
> +	 * If virtual node is not linked, then link with node;
> +	 * otherwise skip
> +	 */
> +	if (!vnode->vnode)
> +		dt_link_virtual(node, vnode);
> +
> +skip:
> +	list_for_each(&node->children, child, list) {
> +		/* If a virtual node is already linked, skip */
> +		if (target_is_virtual(child) && child->vnode)
> +			continue;
> +
> +		pdbg_targets_init_virtual(child, root);
> +	}
> +}
> +
>  void pdbg_targets_init(void *fdt)
>  {
>  	/* Root node needs to be valid when this function returns */
> @@ -665,6 +761,7 @@ void pdbg_targets_init(void *fdt)
>  	}
>  
>  	dt_expand(pdbg_dt_root, fdt);
> +	pdbg_targets_init_virtual(pdbg_dt_root, pdbg_dt_root);
>  }
>  
>  char *pdbg_target_path(struct pdbg_target *target)
>