[PATCH v2 11/28] drm/atomic_sro: Create kernel parameter to force or disable readout

[Maxime Ripard]

The hardware state readout is useful, but might need to be disabled
in case of bugs, or its checks relaxed during development when not
all hooks are implemented yet.

Add a module parameter to control the readout behavior: it can be
disabled entirely, or the checks for missing compare or readout hooks
can be skipped independently.

Suggested-by: Simona Vetter <simona@xxxxxxxx>
Signed-off-by: Maxime Ripard <mripard@xxxxxxxxxx>
---
 drivers/gpu/drm/drm_atomic_sro.c | 36 ++++++++++++++++++++++++++++++++++++
 include/drm/drm_atomic_sro.h     |  2 ++
 2 files changed, 38 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic_sro.c b/drivers/gpu/drm/drm_atomic_sro.c
index 177b97d451f5..a46f06e75c4e 100644
--- a/drivers/gpu/drm/drm_atomic_sro.c
+++ b/drivers/gpu/drm/drm_atomic_sro.c
@@ -11,10 +11,46 @@
 #include <linux/module.h>
 
 #include "drm_internal.h"
 #include "drm_crtc_internal.h"
 
+enum drm_atomic_readout_status {
+	DRM_ATOMIC_READOUT_DISABLED = 0,
+	DRM_ATOMIC_READOUT_ENABLED,
+	DRM_ATOMIC_READOUT_SKIP_MISSING_COMPARE,
+	DRM_ATOMIC_READOUT_SKIP_MISSING_READOUT,
+};
+
+static unsigned int atomic_readout = DRM_ATOMIC_READOUT_ENABLED;
+module_param_unsafe(atomic_readout, uint, 0);
+MODULE_PARM_DESC(atomic_readout,
+		 "Enable Hardware State Readout (0 = disabled, 1 = enabled, 2 = ignore missing compares, 3 = ignore missing readouts and compares, default = 1)");
+
+/**
+ * drm_atomic_sro_device_can_readout - check if a device supports hardware state readout
+ * @dev: DRM device to check
+ *
+ * Verifies that the device is an atomic driver, that readout is
+ * enabled, and that all KMS objects implement the relevant hooks.
+ *
+ * RETURNS:
+ *
+ * True if the device supports full hardware state readout, false
+ * otherwise.
+ */
+bool drm_atomic_sro_device_can_readout(struct drm_device *dev)
+{
+	if (!drm_core_check_feature(dev, DRIVER_ATOMIC))
+		return false;
+
+	if (atomic_readout == DRM_ATOMIC_READOUT_DISABLED)
+		return false;
+
+	return true;
+}
+EXPORT_SYMBOL(drm_atomic_sro_device_can_readout);
+
 struct __drm_atomic_sro_plane {
 	struct drm_plane *ptr;
 	struct drm_plane_state *state;
 };
 
diff --git a/include/drm/drm_atomic_sro.h b/include/drm/drm_atomic_sro.h
index 5a9333a05796..6e5262384c71 100644
--- a/include/drm/drm_atomic_sro.h
+++ b/include/drm/drm_atomic_sro.h
@@ -13,10 +13,12 @@ struct drm_plane;
 struct drm_plane_state;
 struct drm_printer;
 struct drm_private_obj;
 struct drm_private_state;
 
+bool drm_atomic_sro_device_can_readout(struct drm_device *dev);
+
 struct drm_atomic_sro_state *drm_atomic_sro_state_alloc(struct drm_device *dev);
 void drm_atomic_sro_state_free(struct drm_atomic_sro_state *state);
 void drm_atomic_sro_state_print(const struct drm_atomic_sro_state *state,
 				struct drm_printer *p);
 

-- 
2.53.0