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Subject[PATCH v2 1/2] drm: Include ddc adapter pointer in struct drm_connector
Date
Add generic code which creates symbolic links in sysfs, pointing to ddc
interface used by a particular video output. For example:

ls -l /sys/class/drm/card0-HDMI-A-1/ddc
lrwxrwxrwx 1 root root 0 Jun 24 10:42 /sys/class/drm/card0-HDMI-A-1/ddc \
-> ../../../../soc/13880000.i2c/i2c-2

This makes it easy for user to associate a display with its ddc adapter
and use e.g. ddcutil to control the chosen monitor.

This patch adds an i2c_adapter pointer to struct drm_connector. Particular
drivers can then use it instead of using their own private instance. If a
connector contains a ddc, then create a symbolic link in sysfs.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
---
drivers/gpu/drm/drm_sysfs.c | 7 +++++++
include/drm/drm_connector.h | 11 +++++++++++
2 files changed, 18 insertions(+)

diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
index ad10810bc972..26d359b39785 100644
--- a/drivers/gpu/drm/drm_sysfs.c
+++ b/drivers/gpu/drm/drm_sysfs.c
@@ -294,6 +294,9 @@ int drm_sysfs_connector_add(struct drm_connector *connector)
/* Let userspace know we have a new connector */
drm_sysfs_hotplug_event(dev);

+ if (connector->ddc)
+ return sysfs_create_link(&connector->kdev->kobj,
+ &connector->ddc->dev.kobj, "ddc");
return 0;
}

@@ -301,6 +304,10 @@ void drm_sysfs_connector_remove(struct drm_connector *connector)
{
if (!connector->kdev)
return;
+
+ if (connector->ddc)
+ sysfs_remove_link(&connector->kdev->kobj, "ddc");
+
DRM_DEBUG("removing \"%s\" from sysfs\n",
connector->name);

diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index ca745d9feaf5..1ad3d1d54ba7 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -23,6 +23,7 @@
#ifndef __DRM_CONNECTOR_H__
#define __DRM_CONNECTOR_H__

+#include <linux/i2c.h>
#include <linux/list.h>
#include <linux/llist.h>
#include <linux/ctype.h>
@@ -1308,6 +1309,16 @@ struct drm_connector {
* [0]: progressive, [1]: interlaced
*/
int audio_latency[2];
+
+ /**
+ * @ddc: associated ddc adapter.
+ * A connector usually has its associated ddc adapter. If a driver uses
+ * this field, then an appropriate symbolic link is created in connector
+ * sysfs directory to make it easy for the user to tell which i2c
+ * adapter is for a particular display.
+ */
+ struct i2c_adapter *ddc;
+
/**
* @null_edid_counter: track sinks that give us all zeros for the EDID.
* Needed to workaround some HW bugs where we get all 0s
--
2.17.1
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