Re: [PATCH v2 03/16] ACPI: property: Rework acpi_graph_get_next_endpoint()

Laurent Pinchart
2025-09-24T09:40:10Z

Hi Sakari,

On Wed, Sep 24, 2025 at 10:45:49AM +0300, Sakari Ailus wrote:
> Rework the code obtaining the next endpoint in
> acpi_graph_get_next_endpoint(). The resulting code removes unnecessary
> contitionals and should be easier to follow.
>
> Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> ---
> drivers/acpi/property.c | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/acpi/property.c b/drivers/acpi/property.c
> index 3e85900080ac..5438592dc136 100644
> --- a/drivers/acpi/property.c
> +++ b/drivers/acpi/property.c
> @@ -1399,14 +1399,15 @@ static struct fwnode_handle *acpi_graph_get_next_endpoint(
> if (!port)
> return NULL;
>
> - endpoint = acpi_get_next_subnode(port, prev);
> - while (!endpoint) {
> - port = acpi_get_next_subnode(fwnode, port);
> - if (!port)
> + do {
> + endpoint = acpi_get_next_subnode(port, prev);
> + if (endpoint)
> break;
> +
> + port = acpi_get_next_subnode(fwnode, port);
> if (is_acpi_graph_node(port, "port"))
> - endpoint = acpi_get_next_subnode(port, NULL);
> - }
> + prev = NULL;

Isn't there an issue here ? If the next subnode of fwnode is not a port,
the next iteration of the do loop will attempt to get an endpoint from
that non-port node. Maybe the acpi_get_next_subnode() that will try to
get the endpoint from the non-port port will return NULL because prev
won't be a child of port, but that seems fragile.

I think the following would be easier to understand:

do {
endpoint = acpi_get_next_subnode(port, prev);
if (endpoint)
break;

prev = NULL;

do {
port = acpi_get_next_subnode(fwnode, port);
} while (port && !is_acpi_graph_node(port, "port"));
} while (port);

> + } while (port);
>
> /*
> * The names of the endpoint nodes begin with "endpoint@" followed by
>

--
Regards,

Laurent Pinchart