Re: [PATCH 2/4] drm/of: add support to find any enabled endpoint

Sam Ravnborg
2019-12-08T09:31:58Z

Hi Rob.

Patch looks good, one small improvement proposal.

On Sat, Dec 07, 2019 at 12:35:51PM -0800, Rob Clark wrote:
> From: Rob Clark <robdclark@chromium.org>
>
> To handle the case where there are multiple panel endpoints, only one of
> which is enabled/installed, add support for a wildcard endpoint value to
> request finding whichever endpoint is enabled.
>
> Signed-off-by: Rob Clark <robdclark@chromium.org>
> ---
> drivers/gpu/drm/drm_of.c | 41 +++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 40 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> index 0ca58803ba46..2baf44e401b8 100644
> --- a/drivers/gpu/drm/drm_of.c
> +++ b/drivers/gpu/drm/drm_of.c
> @@ -219,11 +219,44 @@ int drm_of_encoder_active_endpoint(struct device_node *node,
> }
> EXPORT_SYMBOL_GPL(drm_of_encoder_active_endpoint);
>
> +static int find_enabled_endpoint(const struct device_node *node, u32 port)
> +{
> + struct device_node *endpoint_node, *remote;
> + u32 endpoint = 0;
> +
> + for (endpoint = 0; ; endpoint++) {
> + endpoint_node = of_graph_get_endpoint_by_regs(node, port, endpoint);
> + if (!endpoint_node) {
> + pr_debug("No more endpoints!\n");
> + return -ENODEV;
> + }
> +
> + remote = of_graph_get_remote_port_parent(endpoint_node);
> + of_node_put(endpoint_node);
> + if (!remote) {
> + pr_debug("no valid remote node\n");
> + continue;
> + }
> +
> + if (!of_device_is_available(remote)) {
> + pr_debug("not available for remote node\n");
> + of_node_put(remote);
> + continue;
> + }
> +
> + pr_debug("found enabled endpoint %d for %s\n", endpoint, remote->name);
> + of_node_put(remote);
> + return endpoint;
> + }
> +
> + return -ENODEV;
> +}
This function seems pretty generic. Should this be part of
drivers/of/property.c - as others may have the same need?

> +
> /**
> * drm_of_find_panel_or_bridge - return connected panel or bridge device
> * @np: device tree node containing encoder output ports
> * @port: port in the device tree node
> - * @endpoint: endpoint in the device tree node
> + * @endpoint: endpoint in the device tree node, or -1 to find an enabled endpoint
> * @panel: pointer to hold returned drm_panel
> * @bridge: pointer to hold returned drm_bridge

Introducing a define would make it easier to use this function in the
right way.
For example:
#define OF_ENDPOINT_FIRST -1

Then we would see this code in the user side:
+ ret = drm_of_find_panel_or_bridge(pdata->dev->of_node, 1,
OF_ENDPOINT_FIRST,
&pdata->panel, NULL);

Or something like this.

Sam

> *
> @@ -246,6 +279,12 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> if (panel)
> *panel = NULL;
>
> + if (endpoint == -1) {
> + endpoint = find_enabled_endpoint(np, port);
> + if (endpoint < 0)
> + return endpoint;
> + }
> +
> remote = of_graph_get_remote_node(np, port, endpoint);
> if (!remote)
> return -ENODEV;
> --
> 2.23.0
>
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