Date:   Sun, 10 Apr 2022 23:10:57 -0500
From:   Frank Rowand <frowand.list@...il.com>
To:     Rob Herring <robh+dt@...nel.org>, pantelis.antoniou@...sulko.com,
        Slawomir Stepien <slawomir.stepien@...ia.com>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Slawomir Stepien <sst@...zta.fm>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Alan Tull <atull@...nel.org>,
        Jan Kiszka <jan.kiszka@...mens.com>
Subject: Re: [PATCH v2 1/2] of: overlay: rename variables to be consistent

adding cc: Jan Kiszka <jan.kiszka@...mens.com>

On 4/10/22 16:08, frowand.list@...il.com wrote:
> From: Frank Rowand <frank.rowand@...y.com>
> 
> Variables change name across function calls when there is not a good
> reason to do so.  Fix by changing "fdt" to "new_fdt" and "tree" to
> "overlay_tree".
> 
> The name disparity was confusing when creating the following commit.
> The name changes are in this separate commit to make review of the
> following commmit less complex.
> 
> Signed-off-by: Frank Rowand <frank.rowand@...y.com>
> ---
> Changes since v1:
>   - This patch is added to the series.
> 
>  drivers/of/overlay.c | 94 ++++++++++++++++++++++----------------------
>  1 file changed, 47 insertions(+), 47 deletions(-)
> 
> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
> index d80160cf34bb..f74aa9ff67aa 100644
> --- a/drivers/of/overlay.c
> +++ b/drivers/of/overlay.c
> @@ -57,7 +57,7 @@ struct fragment {
>   * struct overlay_changeset
>   * @id:			changeset identifier
>   * @ovcs_list:		list on which we are located
> - * @fdt:		base of memory allocated to hold aligned FDT that was unflattened to create @overlay_tree
> + * @new_fdt:		Memory allocated to hold unflattened aligned FDT
>   * @overlay_tree:	expanded device tree that contains the fragment nodes
>   * @count:		count of fragment structures
>   * @fragments:		fragment nodes in the overlay expanded device tree
> @@ -67,7 +67,7 @@ struct fragment {
>  struct overlay_changeset {
>  	int id;
>  	struct list_head ovcs_list;
> -	const void *fdt;
> +	const void *new_fdt;
>  	struct device_node *overlay_tree;
>  	int count;
>  	struct fragment *fragments;
> @@ -718,19 +718,20 @@ static struct device_node *find_target(struct device_node *info_node)
>  
>  /**
>   * init_overlay_changeset() - initialize overlay changeset from overlay tree
> - * @ovcs:	Overlay changeset to build
> - * @fdt:	base of memory allocated to hold aligned FDT that was unflattened to create @tree
> - * @tree:	Contains the overlay fragments and overlay fixup nodes
> + * @ovcs:		Overlay changeset to build
> + * @new_fdt:		Memory allocated to hold unflattened aligned FDT
> + * @overlay_tree:	Contains the overlay fragments and overlay fixup nodes
>   *
>   * Initialize @ovcs.  Populate @ovcs->fragments with node information from
> - * the top level of @tree.  The relevant top level nodes are the fragment
> - * nodes and the __symbols__ node.  Any other top level node will be ignored.
> + * the top level of @overlay_tree.  The relevant top level nodes are the
> + * fragment nodes and the __symbols__ node.  Any other top level node will
> + * be ignored.
>   *
>   * Return: 0 on success, -ENOMEM if memory allocation failure, -EINVAL if error
> - * detected in @tree, or -ENOSPC if idr_alloc() error.
> + * detected in @overlay_tree, or -ENOSPC if idr_alloc() error.
>   */
>  static int init_overlay_changeset(struct overlay_changeset *ovcs,
> -		const void *fdt, struct device_node *tree)
> +		const void *new_fdt, struct device_node *overlay_tree)
>  {
>  	struct device_node *node, *overlay_node;
>  	struct fragment *fragment;
> @@ -741,17 +742,17 @@ static int init_overlay_changeset(struct overlay_changeset *ovcs,
>  	 * Warn for some issues.  Can not return -EINVAL for these until
>  	 * of_unittest_apply_overlay() is fixed to pass these checks.
>  	 */
> -	if (!of_node_check_flag(tree, OF_DYNAMIC))
> -		pr_debug("%s() tree is not dynamic\n", __func__);
> +	if (!of_node_check_flag(overlay_tree, OF_DYNAMIC))
> +		pr_debug("%s() overlay_tree is not dynamic\n", __func__);
>  
> -	if (!of_node_check_flag(tree, OF_DETACHED))
> -		pr_debug("%s() tree is not detached\n", __func__);
> +	if (!of_node_check_flag(overlay_tree, OF_DETACHED))
> +		pr_debug("%s() overlay_tree is not detached\n", __func__);
>  
> -	if (!of_node_is_root(tree))
> -		pr_debug("%s() tree is not root\n", __func__);
> +	if (!of_node_is_root(overlay_tree))
> +		pr_debug("%s() overlay_tree is not root\n", __func__);
>  
> -	ovcs->overlay_tree = tree;
> -	ovcs->fdt = fdt;
> +	ovcs->overlay_tree = overlay_tree;
> +	ovcs->new_fdt = new_fdt;
>  
>  	INIT_LIST_HEAD(&ovcs->ovcs_list);
>  
> @@ -764,7 +765,7 @@ static int init_overlay_changeset(struct overlay_changeset *ovcs,
>  	cnt = 0;
>  
>  	/* fragment nodes */
> -	for_each_child_of_node(tree, node) {
> +	for_each_child_of_node(overlay_tree, node) {
>  		overlay_node = of_get_child_by_name(node, "__overlay__");
>  		if (overlay_node) {
>  			cnt++;
> @@ -772,7 +773,7 @@ static int init_overlay_changeset(struct overlay_changeset *ovcs,
>  		}
>  	}
>  
> -	node = of_get_child_by_name(tree, "__symbols__");
> +	node = of_get_child_by_name(overlay_tree, "__symbols__");
>  	if (node) {
>  		cnt++;
>  		of_node_put(node);
> @@ -785,7 +786,7 @@ static int init_overlay_changeset(struct overlay_changeset *ovcs,
>  	}
>  
>  	cnt = 0;
> -	for_each_child_of_node(tree, node) {
> +	for_each_child_of_node(overlay_tree, node) {
>  		overlay_node = of_get_child_by_name(node, "__overlay__");
>  		if (!overlay_node)
>  			continue;
> @@ -807,7 +808,7 @@ static int init_overlay_changeset(struct overlay_changeset *ovcs,
>  	 * if there is a symbols fragment in ovcs->fragments[i] it is
>  	 * the final element in the array
>  	 */
> -	node = of_get_child_by_name(tree, "__symbols__");
> +	node = of_get_child_by_name(overlay_tree, "__symbols__");
>  	if (node) {
>  		ovcs->symbols_fragment = 1;
>  		fragment = &fragments[cnt];
> @@ -862,11 +863,11 @@ static void free_overlay_changeset(struct overlay_changeset *ovcs)
>  	kfree(ovcs->fragments);
>  	/*
>  	 * There should be no live pointers into ovcs->overlay_tree and
> -	 * ovcs->fdt due to the policy that overlay notifiers are not allowed
> -	 * to retain pointers into the overlay devicetree.
> +	 * ovcs->new_fdt due to the policy that overlay notifiers are not
> +	 * allowed to retain pointers into the overlay devicetree.
>  	 */
>  	kfree(ovcs->overlay_tree);
> -	kfree(ovcs->fdt);
> +	kfree(ovcs->new_fdt);
>  	kfree(ovcs);
>  }
>  
> @@ -874,16 +875,15 @@ static void free_overlay_changeset(struct overlay_changeset *ovcs)
>   * internal documentation
>   *
>   * of_overlay_apply() - Create and apply an overlay changeset
> - * @fdt:	base of memory allocated to hold the aligned FDT
> - * @tree:	Expanded overlay device tree
> - * @ovcs_id:	Pointer to overlay changeset id
> + * @new_fdt:		Memory allocated to hold the aligned FDT
> + * @overlay_tree:	Expanded overlay device tree
> + * @ovcs_id:		Pointer to overlay changeset id
>   *
>   * Creates and applies an overlay changeset.
>   *
>   * If an error occurs in a pre-apply notifier, then no changes are made
>   * to the device tree.
>   *
> -
>   * A non-zero return value will not have created the changeset if error is from:
>   *   - parameter checks
>   *   - building the changeset
> @@ -913,29 +913,29 @@ static void free_overlay_changeset(struct overlay_changeset *ovcs)
>   * id is returned to *ovcs_id.
>   */
>  
> -static int of_overlay_apply(const void *fdt, struct device_node *tree,
> -		int *ovcs_id)
> +static int of_overlay_apply(const void *new_fdt,
> +		struct device_node *overlay_tree, int *ovcs_id)
>  {
>  	struct overlay_changeset *ovcs;
>  	int ret = 0, ret_revert, ret_tmp;
>  
>  	/*
> -	 * As of this point, fdt and tree belong to the overlay changeset.
> -	 * overlay changeset code is responsible for freeing them.
> +	 * As of this point, new_fdt and overlay_tree belong to the overlay
> +	 * changeset.  overlay changeset code is responsible for freeing them.
>  	 */
>  
>  	if (devicetree_corrupt()) {
>  		pr_err("devicetree state suspect, refuse to apply overlay\n");
> -		kfree(fdt);
> -		kfree(tree);
> +		kfree(new_fdt);
> +		kfree(overlay_tree);
>  		ret = -EBUSY;
>  		goto out;
>  	}
>  
>  	ovcs = kzalloc(sizeof(*ovcs), GFP_KERNEL);
>  	if (!ovcs) {
> -		kfree(fdt);
> -		kfree(tree);
> +		kfree(new_fdt);
> +		kfree(overlay_tree);
>  		ret = -ENOMEM;
>  		goto out;
>  	}
> @@ -943,20 +943,20 @@ static int of_overlay_apply(const void *fdt, struct device_node *tree,
>  	of_overlay_mutex_lock();
>  	mutex_lock(&of_mutex);
>  
> -	ret = of_resolve_phandles(tree);
> +	ret = of_resolve_phandles(overlay_tree);
>  	if (ret)
> -		goto err_free_tree;
> +		goto err_free_overlay_tree;
>  
> -	ret = init_overlay_changeset(ovcs, fdt, tree);
> +	ret = init_overlay_changeset(ovcs, new_fdt, overlay_tree);
>  	if (ret)
> -		goto err_free_tree;
> +		goto err_free_overlay_tree;
>  
>  	/*
>  	 * after overlay_notify(), ovcs->overlay_tree related pointers may have
> -	 * leaked to drivers, so can not kfree() tree, aka ovcs->overlay_tree;
> -	 * and can not free memory containing aligned fdt.  The aligned fdt
> -	 * is contained within the memory at ovcs->fdt, possibly at an offset
> -	 * from ovcs->fdt.
> +	 * leaked to drivers, so can not kfree() overlay_tree,
> +	 * aka ovcs->overlay_tree; and can not free memory containing aligned
> +	 * fdt.  The aligned fdt is contained within the memory at
> +	 * ovcs->new_fdt, possibly at an offset from ovcs->new_fdt.
>  	 */
>  	ret = overlay_notify(ovcs, OF_OVERLAY_PRE_APPLY);
>  	if (ret) {
> @@ -997,9 +997,9 @@ static int of_overlay_apply(const void *fdt, struct device_node *tree,
>  
>  	goto out_unlock;
>  
> -err_free_tree:
> -	kfree(fdt);
> -	kfree(tree);
> +err_free_overlay_tree:
> +	kfree(new_fdt);
> +	kfree(overlay_tree);
>  
>  err_free_overlay_changeset:
>  	free_overlay_changeset(ovcs);

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