[V4,1/3] core/device: Add function to return child node using name at substring "@"

Add a function dt_find_by_name_substr() that returns the child node if
it matches till first occurence at "@" of a given name, otherwise NULL.
This is helpful for cases with node name like: "name@addr". In
scenarios where nodes are added with "name@addr" format and if the
value of "addr" is not known, that node can't be matched with node
name or addr. Hence matching with substring as node name will return
the expected result. Patch adds dt_find_by_name_substr() function
and testcase for the same in core/test/run-device.c

Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Reviewed-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
---
Changelog:
v3 -> v4:
- Addressed review comment from Mahesh and added his Reviewed-by.

v2 -> v3:
- After review comments from Mahesh, fixed the code
  to consider string upto "@" for both input node name
  as well as child node name. V2 version was comparing
  input node name and child node name upto string length
  of child name. But this will return wrong node if input
  name is larger than child name. Because it will match
  as substring for child name.
  https://lists.ozlabs.org/pipermail/skiboot/2023-January/018596.html

v1 -> v2:
- Addressed review comment from Dan to update
  the utility funtion to search and compare
  upto "@". Renamed it as dt_find_by_name_substr.

 core/device.c          | 31 +++++++++++++++++++++++++++++++
 core/test/run-device.c | 15 +++++++++++++++
 include/device.h       |  3 +++
 3 files changed, 49 insertions(+)

> On 06-Mar-2023, at 9:09 AM, Athira Rajeev <atrajeev@linux.vnet.ibm.com> wrote:
> 
> Add a function dt_find_by_name_substr() that returns the child node if
> it matches till first occurence at "@" of a given name, otherwise NULL.
> This is helpful for cases with node name like: "name@addr". In
> scenarios where nodes are added with "name@addr" format and if the
> value of "addr" is not known, that node can't be matched with node
> name or addr. Hence matching with substring as node name will return
> the expected result. Patch adds dt_find_by_name_substr() function
> and testcase for the same in core/test/run-device.c
> 
> Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
> Reviewed-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
> ---
> Changelog:
> v3 -> v4:
> - Addressed review comment from Mahesh and added his Reviewed-by.
Hi,

Looking for review comments. Please share feedback.

Thanks
Athira
> 
> v2 -> v3:
> - After review comments from Mahesh, fixed the code
>  to consider string upto "@" for both input node name
>  as well as child node name. V2 version was comparing
>  input node name and child node name upto string length
>  of child name. But this will return wrong node if input
>  name is larger than child name. Because it will match
>  as substring for child name.
>  https://lists.ozlabs.org/pipermail/skiboot/2023-January/018596.html
> 
> v1 -> v2:
> - Addressed review comment from Dan to update
>  the utility funtion to search and compare
>  upto "@". Renamed it as dt_find_by_name_substr.
> 
> core/device.c          | 31 +++++++++++++++++++++++++++++++
> core/test/run-device.c | 15 +++++++++++++++
> include/device.h       |  3 +++
> 3 files changed, 49 insertions(+)
> 
> diff --git a/core/device.c b/core/device.c
> index b102dd97..6b457ec4 100644
> --- a/core/device.c
> +++ b/core/device.c
> @@ -395,6 +395,37 @@ struct dt_node *dt_find_by_name(struct dt_node *root, const char *name)
> }
> 
> 
> +struct dt_node *dt_find_by_name_substr(struct dt_node *root, const char *name)
> +{
> +	struct dt_node *child, *match;
> +	char *node, *child_node = NULL;
> +
> +	node = strdup(name);
> +	if (!node)
> +		return NULL;
> +	node = strtok(node, "@");
> +	list_for_each(&root->children, child, list) {
> +		child_node = strdup(child->name);
> +		if (!child_node)
> +			goto err;
> +		child_node = strtok(child_node, "@");
> +		if (!strcmp(child_node, node)) {
> +			free(child_node);
> +			free(node);
> +			return child;
> +		}
> +
> +		match = dt_find_by_name_substr(child, name);
> +		if (match)
> +			return match;
> +	}
> +
> +	free(child_node);
> +err:
> +	free(node);
> +	return NULL;
> +}
> +
> struct dt_node *dt_new_check(struct dt_node *parent, const char *name)
> {
> 	struct dt_node *node = dt_find_by_name(parent, name);
> diff --git a/core/test/run-device.c b/core/test/run-device.c
> index 4a12382b..6997452e 100644
> --- a/core/test/run-device.c
> +++ b/core/test/run-device.c
> @@ -466,6 +466,21 @@ int main(void)
> 	new_prop_ph = dt_prop_get_u32(ut2, "something");
> 	assert(!(new_prop_ph == ev1_ph));
> 	dt_free(subtree);
> +
> +	/* Test dt_find_by_name_substr */
> +	root = dt_new_root("");
> +	addr1 = dt_new_addr(root, "node", 0x1);
> +	addr2 = dt_new_addr(root, "node0_1", 0x2);
> +	assert(dt_find_by_name(root, "node@1") == addr1);
> +	assert(dt_find_by_name(root, "node0_1@2") == addr2);
> +	assert(dt_find_by_name_substr(root, "node@1") == addr1);
> +	assert(dt_find_by_name_substr(root, "node0_1@2") == addr2);
> +	assert(dt_find_by_name_substr(root, "node0_") == NULL);
> +	assert(dt_find_by_name_substr(root, "node0_1") == addr2);
> +	assert(dt_find_by_name_substr(root, "node0@") == NULL);
> +	assert(dt_find_by_name_substr(root, "node0_@") == NULL);
> +	dt_free(root);
> +
> 	return 0;
> }
> 
> diff --git a/include/device.h b/include/device.h
> index 93fb90ff..b6a1a813 100644
> --- a/include/device.h
> +++ b/include/device.h
> @@ -184,6 +184,9 @@ struct dt_node *dt_find_by_path(struct dt_node *root, const char *path);
> /* Find a child node by name */
> struct dt_node *dt_find_by_name(struct dt_node *root, const char *name);
> 
> +/* Find a child node by name and substring */
> +struct dt_node *dt_find_by_name_substr(struct dt_node *root, const char *name);
> +
> /* Find a node by phandle */
> struct dt_node *dt_find_by_phandle(struct dt_node *root, u32 phandle);
> 
> -- 
> 2.31.1
>

Hi Athira,

On Mon, Mar 06, 2023 at 09:09:11AM +0530, Athira Rajeev wrote:
>Add a function dt_find_by_name_substr() that returns the child node if
>it matches till first occurence at "@" of a given name, otherwise NULL.

Given this summary, I don't understand the following:

>+	assert(dt_find_by_name_substr(root, "node@1") == addr1);
>+	assert(dt_find_by_name_substr(root, "node0_1@2") == addr2);

Is this behavior required? I don't think it makes sense to call this 
function with a second argument containing '@', so I wouldn't expect it 
to match anything in these cases. The function seems to specifically 
enable it:

>+struct dt_node *dt_find_by_name_substr(struct dt_node *root, const char *name)
>+{
[snip]
>+      node = strdup(name);
>+      if (!node)
>+              return NULL;
>+      node = strtok(node, "@");

Seems like you could get rid of this and just use name as-is.

I was curious about something else; say we have 'node@1' and 'node@2'.  
Is there an expectation of which it should match?

     addr1 = dt_new_addr(root, "node", 0x1);
     addr2 = dt_new_addr(root, "node", 0x2);
     assert(dt_find_by_name_substr(root, "node") == ???????);
                                                    ^^^^^^^

>+/* Find a child node by name and substring */
>+struct dt_node *dt_find_by_name_substr(struct dt_node *root, const char *name);

I think this name fit better in previous versions of the patch, but 
since you're specifically looking for '@' now, maybe call it something 
like dt_find_by_name_before_addr?