Re: [PATCH V7 1/4] drm: of: Add drm_of_get_dsi_bus helper function

[Sam Ravnborg <sam@ravnborg.org>]

Hi Chris.

On Tue, Jan 03, 2023 at 01:07:04PM -0600, Chris Morgan wrote:
> From: Chris Morgan <macromorgan@hotmail.com>
> 
> Add helper function to find DSI host for devices where DSI panel is not
> a minor of a DSI bus (such as the Samsung AMS495QA01 panel or the
> official Raspberry Pi touchscreen display).
> 
> Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
> Signed-off-by: Maya Matuszczyk <maccraft123mc@gmail.com>
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> ---
>  drivers/gpu/drm/drm_of.c | 62 ++++++++++++++++++++++++++++++++++++++++
>  include/drm/drm_of.h     | 11 +++++++
>  2 files changed, 73 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
> index 7bbcb999bb75..7d89ac164069 100644
> --- a/drivers/gpu/drm/drm_of.c
> +++ b/drivers/gpu/drm/drm_of.c
> @@ -10,6 +10,7 @@
>  #include <drm/drm_crtc.h>
>  #include <drm/drm_device.h>
>  #include <drm/drm_encoder.h>
> +#include <drm/drm_mipi_dsi.h>
>  #include <drm/drm_of.h>
>  #include <drm/drm_panel.h>
>  
> @@ -493,3 +494,64 @@ int drm_of_get_data_lanes_count_ep(const struct device_node *port,
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(drm_of_get_data_lanes_count_ep);
> +
> +/**
> + * drm_of_get_dsi_bus - find the DSI bus for a given device
> + * @dev: parent device of display (SPI, I2C)
> + * @dsi_host: DSI host to be populated
> + * @info: DSI device info to be updated with correct DSI node
> + *
> + * Given a panel device parented to a non-DSI device, follow the
> + * devicetree to find the correct DSI host node and populate the
> + * dsi_host with the correct host and info with the correct node.

I think you need and empty line before Returns ...
This is what others does in the same file, so for consistency please add
it.

With this detail fixed:
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>

> + * Returns zero if successful, -EPROBE_DEFER if the DSI host is
> + * found but not available, or -ENODEV otherwise.
> + */
> +int drm_of_get_dsi_bus(struct device *dev,
> +			      struct mipi_dsi_host **dsi_host,
> +			      struct mipi_dsi_device_info *info)
> +{
> +	struct device_node *endpoint, *dsi_host_node;
> +
> +	/*
> +	 * Get first endpoint child from device.
> +	 */
> +	endpoint = of_graph_get_next_endpoint(dev->of_node, NULL);
> +	if (!endpoint)
> +		return -ENODEV;
> +
> +	/*
> +	 * Follow the first endpoint to get the DSI host node.
> +	 */
> +	dsi_host_node = of_graph_get_remote_port_parent(endpoint);
> +	if (!dsi_host_node)
> +		goto error;
> +
> +	/*
> +	 * Get the DSI host from the DSI host node. If we get an error
> +	 * or the return is null assume we're not ready to probe just
> +	 * yet. Release the DSI host node since we're done with it.
> +	 */
> +	*dsi_host = of_find_mipi_dsi_host_by_node(dsi_host_node);
> +	of_node_put(dsi_host_node);
> +	if (IS_ERR_OR_NULL(*dsi_host)) {
> +		of_node_put(endpoint);
> +		return -EPROBE_DEFER;
> +	}
> +
> +	/*
> +	 * Set the node of the mipi_dsi_device_info to the correct node
> +	 * and then release the endpoint node since we're done with it.
> +	 */
> +	info->node = of_graph_get_remote_port(endpoint);
> +	if (IS_ERR_OR_NULL(info->node))
> +		goto error;
> +
> +	of_node_put(endpoint);
> +	return 0;
> +
> +error:
> +	of_node_put(endpoint);
> +	return -ENODEV;
> +}
> +EXPORT_SYMBOL_GPL(drm_of_get_dsi_bus);
> diff --git a/include/drm/drm_of.h b/include/drm/drm_of.h
> index 10ab58c40746..e27061b02315 100644
> --- a/include/drm/drm_of.h
> +++ b/include/drm/drm_of.h
> @@ -15,6 +15,8 @@ struct drm_encoder;
>  struct drm_panel;
>  struct drm_bridge;
>  struct device_node;
> +struct mipi_dsi_device_info;
> +struct mipi_dsi_host;
>  
>  /**
>   * enum drm_lvds_dual_link_pixels - Pixel order of an LVDS dual-link connection
> @@ -56,6 +58,9 @@ int drm_of_get_data_lanes_count_ep(const struct device_node *port,
>  				   int port_reg, int reg,
>  				   const unsigned int min,
>  				   const unsigned int max);
> +int drm_of_get_dsi_bus(struct device *dev,
> +		       struct mipi_dsi_host **dsi_host,
> +		       struct mipi_dsi_device_info *info);
>  #else
>  static inline uint32_t drm_of_crtc_port_mask(struct drm_device *dev,
>  					  struct device_node *port)
> @@ -127,6 +132,12 @@ drm_of_get_data_lanes_count_ep(const struct device_node *port,
>  {
>  	return -EINVAL;
>  }
> +static int drm_of_get_dsi_bus(struct device *dev,
> +			      struct mipi_dsi_host **dsi_host,
> +			      struct mipi_dsi_device_info *info)
> +{
> +	return -EINVAL;
> +}
>  #endif
>  
>  /*
> -- 
> 2.34.1