Hi Jani,
Thanks for the review.
On 8/31/2026 7:19 PM, Jani Nikula wrote:
On Wed, 26 Aug 2026, Naladala Ramanaidu <[email protected]> wrote:
Add an i915_hdmi_force_bit_banging debugfs control for HDMI
connectors to allow EDID reads to be forced over GPIO bit-banging.
The primary question the commit message *must* answer is *why*.
It takes me under a minute to look at the patch and deduce the *what*,
and even that does not match the commit message. There is no support for
actually forcing anything here, it's just the non-functional debugfs
being added.
I still have no clue why.
Sure. I'll fold this 2 patches into single patch and i will address it
in the next revision.
Assisted-by: Claude:claude-opus-5
Signed-off-by: Naladala Ramanaidu <[email protected]>
---
.../drm/i915/display/intel_display_debugfs.c | 1 +
.../drm/i915/display/intel_display_types.h | 3 ++
drivers/gpu/drm/i915/display/intel_hdmi.c | 51 +++++++++++++++++++
drivers/gpu/drm/i915/display/intel_hdmi.h | 2 +
4 files changed, 57 insertions(+)
diff --git a/drivers/gpu/drm/i915/display/intel_display_debugfs.c
b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
index 3e302f23f247..c991f224b4be 100644
--- a/drivers/gpu/drm/i915/display/intel_display_debugfs.c
+++ b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
@@ -1335,6 +1335,7 @@ void intel_connector_debugfs_add(struct intel_connector
*connector)
intel_dp_link_training_debugfs_add(connector);
intel_dp_link_caps_debugfs_add(connector);
intel_link_bw_connector_debugfs_add(connector);
+ intel_hdmi_connector_debugfs_add(connector);
if (DISPLAY_VER(display) >= 11 &&
((connector_type == DRM_MODE_CONNECTOR_DisplayPort &&
!connector->mst.dp) ||
diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h
b/drivers/gpu/drm/i915/display/intel_display_types.h
index 20a07ea06b5e..58983e31c5ef 100644
--- a/drivers/gpu/drm/i915/display/intel_display_types.h
+++ b/drivers/gpu/drm/i915/display/intel_display_types.h
@@ -1689,6 +1689,9 @@ struct intel_hdmi {
} dp_dual_mode;
struct intel_connector *attached_connector;
struct cec_notifier *cec_notifier;
+
+ /* Debugfs knob to force EDID reads over GPIO bit-banging. */
Is that comment helpful?
+ bool force_bit_banging;
};
struct intel_dp_mst_encoder;
diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c
b/drivers/gpu/drm/i915/display/intel_hdmi.c
index 9b637e38a1a5..38915f19d3e5 100644
--- a/drivers/gpu/drm/i915/display/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
@@ -26,6 +26,7 @@
* Jesse Barnes <[email protected]>
*/
+#include <linux/debugfs.h>
#include <linux/delay.h>
#include <linux/hdmi.h>
#include <linux/i2c.h>
@@ -3112,6 +3113,56 @@ void intel_infoframe_init(struct intel_digital_port
*dig_port)
}
}
+static int i915_hdmi_force_bit_banging_show(void *data, u64 *val)
Please don't use i915_ naming.
I will drop the i915_ prefix. I will rename it in the next revision.
+{
+ struct intel_connector *connector = to_intel_connector(data);
+
+ *val = READ_ONCE(intel_attached_hdmi(connector)->force_bit_banging);
+
+ return 0;
+}
+
+static int i915_hdmi_force_bit_banging_write(void *data, u64 val)
+{
+ struct intel_connector *connector = to_intel_connector(data);
+ struct intel_display *display = to_intel_display(connector);
+ struct intel_hdmi *intel_hdmi = intel_attached_hdmi(connector);
+
+ if (val > 1)
+ return -EINVAL;
+
+ drm_dbg_kms(display->drm,
+ "[CONNECTOR:%d:%s] %sabling forced GPIO bit-banging for EDID
reads\n",
+ connector->base.base.id, connector->base.name,
+ val ? "en" : "dis");
I see this cute "%sabling" and val ? "en" : "dis" but it's just too
clever for its own good. str_enable_disable() is close enough.
Sure Jani. I will fix this in next revision.
+
+ WRITE_ONCE(intel_hdmi->force_bit_banging, val);
+
+ return 0;
+}
+DEFINE_DEBUGFS_ATTRIBUTE(i915_hdmi_force_bit_banging_fops,
+ i915_hdmi_force_bit_banging_show,
+ i915_hdmi_force_bit_banging_write, "%llu\n");
+
+/**
+ * intel_hdmi_connector_debugfs_add - add HDMI specific connector debugfs files
+ * @connector: pointer to a registered intel_connector
+ *
+ * Cleanup will be done by drm_connector_unregister() through a call to
+ * drm_debugfs_connector_remove().
+ */
+void intel_hdmi_connector_debugfs_add(struct intel_connector *connector)
+{
+ struct dentry *root = connector->base.debugfs_entry;
+
+ if (connector->base.connector_type != DRM_MODE_CONNECTOR_HDMIA &&
+ connector->base.connector_type != DRM_MODE_CONNECTOR_HDMIB)
+ return;
+
+ debugfs_create_file("i915_hdmi_force_bit_banging", 0644, root,
+ connector, &i915_hdmi_force_bit_banging_fops);
Please no new i915_ prefixed naming for shared display code. Please just
use intel_.
+}
+
bool intel_hdmi_init_connector(struct intel_digital_port *dig_port,
struct intel_connector *intel_connector)
{
diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.h
b/drivers/gpu/drm/i915/display/intel_hdmi.h
index c95ed37bcc0c..752cccf5ccee 100644
--- a/drivers/gpu/drm/i915/display/intel_hdmi.h
+++ b/drivers/gpu/drm/i915/display/intel_hdmi.h
@@ -78,4 +78,6 @@ void intel_hdmi_poll_for_scrambling_enable(const struct
intel_crtc_state *crtc_s
int intel_hdmi_sink_max_frl_rate(struct drm_connector *connector);
int intel_hdmi_sink_dsc_max_frl_rate(struct drm_connector *connector);
+void intel_hdmi_connector_debugfs_add(struct intel_connector *connector);
+
#endif /* __INTEL_HDMI_H__ */
