mipi_dsi_devices are inherently aware of their host because they
share a parent-child hierarchy in the device tree.

Non-dsi drivers that create a dummy dsi device don't have this data.
In order to get this information, they require to a phandle to the dsi
host in the device tree.

Maintain a list of all the hosts DSI that are currently registered.

This list will be used to find the mipi_dsi_host corresponding to the
device_node passed in of_find_mipi_dsi_host_by_node.

Signed-off-by: Archit Taneja <arch...@codeaurora.org>
---
 drivers/gpu/drm/drm_mipi_dsi.c | 30 ++++++++++++++++++++++++++++++
 include/drm/drm_mipi_dsi.h     |  2 ++
 2 files changed, 32 insertions(+)

diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
index cbb7373..c51d73e 100644
--- a/drivers/gpu/drm/drm_mipi_dsi.c
+++ b/drivers/gpu/drm/drm_mipi_dsi.c
@@ -216,6 +216,28 @@ of_mipi_dsi_device_add(struct mipi_dsi_host *host, struct 
device_node *node)
        return mipi_dsi_device_new(host, &info);
 }
 
+static DEFINE_MUTEX(host_lock);
+static LIST_HEAD(host_list);
+
+struct mipi_dsi_host *of_find_mipi_dsi_host_by_node(struct device_node *node)
+{
+       struct mipi_dsi_host *host;
+
+       mutex_lock(&host_lock);
+
+       list_for_each_entry(host, &host_list, list) {
+               if (host->dev->of_node == node) {
+                       mutex_unlock(&host_lock);
+                       return host;
+               }
+       }
+
+       mutex_unlock(&host_lock);
+
+       return NULL;
+}
+EXPORT_SYMBOL(of_find_mipi_dsi_host_by_node);
+
 int mipi_dsi_host_register(struct mipi_dsi_host *host)
 {
        struct device_node *node;
@@ -227,6 +249,10 @@ int mipi_dsi_host_register(struct mipi_dsi_host *host)
                of_mipi_dsi_device_add(host, node);
        }
 
+       mutex_lock(&host_lock);
+       list_add_tail(&host->list, &host_list);
+       mutex_unlock(&host_lock);
+
        return 0;
 }
 EXPORT_SYMBOL(mipi_dsi_host_register);
@@ -243,6 +269,10 @@ static int mipi_dsi_remove_device_fn(struct device *dev, 
void *priv)
 void mipi_dsi_host_unregister(struct mipi_dsi_host *host)
 {
        device_for_each_child(host->dev, NULL, mipi_dsi_remove_device_fn);
+
+       mutex_lock(&host_lock);
+       list_del_init(&host->list);
+       mutex_unlock(&host_lock);
 }
 EXPORT_SYMBOL(mipi_dsi_host_unregister);
 
diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
index 68f49f4..15d3068 100644
--- a/include/drm/drm_mipi_dsi.h
+++ b/include/drm/drm_mipi_dsi.h
@@ -100,10 +100,12 @@ struct mipi_dsi_host_ops {
 struct mipi_dsi_host {
        struct device *dev;
        const struct mipi_dsi_host_ops *ops;
+       struct list_head list;
 };
 
 int mipi_dsi_host_register(struct mipi_dsi_host *host);
 void mipi_dsi_host_unregister(struct mipi_dsi_host *host);
+struct mipi_dsi_host *of_find_mipi_dsi_host_by_node(struct device_node *node);
 
 /* DSI mode flags */
 
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
hosted by The Linux Foundation

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