drm/debug: Expose connector's max supported bpc via debugfs

It's useful to know the connector's max supported bpc for IGT
testing. Expose it via a debugfs file on the connector "output_bpc".

Example: cat /sys/kernel/debug/dri/0/DP-1/output_bpc

V2:
* Fix typo in comments (Harry)

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Bhanuprakash Modem <bhanuprakash.modem@intel.com>
Reviewed-by: Arun R Murthy <arun.r.murthy@intel.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220519095149.3560034-2-bhanuprakash.modem@intel.com

diff --git a/drivers/gpu/drm/drm_debugfs.c b/drivers/gpu/drm/drm_debugfs.c
index 7f1b82dbaebb90dbfdc91c47a0fb0b9932a994e4..fb04b7a984de848cd4c55ad682e734930b6bf16a 100644 (file)
--- a/drivers/gpu/drm/drm_debugfs.c
+++ b/drivers/gpu/drm/drm_debugfs.c
@@ -395,6 +395,23 @@ static int vrr_range_show(struct seq_file *m, void *data)
 }
 DEFINE_SHOW_ATTRIBUTE(vrr_range);
 
+/*
+ * Returns Connector's max supported bpc through debugfs file.
+ * Example usage: cat /sys/kernel/debug/dri/0/DP-1/output_bpc
+ */
+static int output_bpc_show(struct seq_file *m, void *data)
+{
+       struct drm_connector *connector = m->private;
+
+       if (connector->status != connector_status_connected)
+               return -ENODEV;
+
+       seq_printf(m, "Maximum: %u\n", connector->display_info.bpc);
+
+       return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(output_bpc);
+
 static const struct file_operations drm_edid_fops = {
        .owner = THIS_MODULE,
        .open = edid_open,
@@ -437,6 +454,10 @@ void drm_debugfs_connector_add(struct drm_connector *connector)
        debugfs_create_file("vrr_range", S_IRUGO, root, connector,
                            &vrr_range_fops);
 
+       /* max bpc */
+       debugfs_create_file("output_bpc", 0444, root, connector,
+                           &output_bpc_fops);
+
        if (connector->funcs->debugfs_init)
                connector->funcs->debugfs_init(connector, root);
 }