[PATCH v3 2/2] drm: add backwards compatibility support for drm_kms_helper.edid_firmware

[Jani Nikula]

If drm_kms_helper.edid_firmware module parameter is set at
drm_kms_helper probe time, update the new drm.edid_firmware parameter
for backwards compatibility.

The drm_kms_helper.edid_firmware is now read-only in sysfs to prevent
runtime updates.

This is a sort of easy middle ground; adding a full runtime support via
/sys/module/drm_kms_helper/parameters/edid_firmware would be possible,
but considerably more and uglier code.

Cc: Abdiel Janulgue <abdiel.janulgue at linux.intel.com>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula at intel.com>

---

I'm wondering if the change from drm_kms_helper.edid_firmware to
drm.edid_firmware is enough of an ABI breakage to warrant something like
this patch.
---
 drivers/gpu/drm/drm_edid_load.c         |  7 +++++++
 drivers/gpu/drm/drm_kms_helper_common.c | 19 +++++++++++++++++++
 include/drm/drm_edid.h                  |  2 ++
 3 files changed, 28 insertions(+)

diff --git a/drivers/gpu/drm/drm_edid_load.c b/drivers/gpu/drm/drm_edid_load.c
index 1c0495acf341..a94005529cd4 100644
--- a/drivers/gpu/drm/drm_edid_load.c
+++ b/drivers/gpu/drm/drm_edid_load.c
@@ -31,6 +31,13 @@ module_param_string(edid_firmware, edid_firmware, sizeof(edid_firmware), 0644);
 MODULE_PARM_DESC(edid_firmware, "Do not probe monitor, use specified EDID blob "
 	"from built-in data or /lib/firmware instead. ");
 
+/* Use only for backward compatibility with drm_kms_helper.edid_firmware */
+void __drm_set_edid_firmware_path(const char *path)
+{
+	strlcpy(edid_firmware, path, sizeof(edid_firmware));
+}
+EXPORT_SYMBOL(__drm_set_edid_firmware_path);
+
 #define GENERIC_EDIDS 6
 static const char * const generic_edid_name[GENERIC_EDIDS] = {
 	"edid/800x600.bin",
diff --git a/drivers/gpu/drm/drm_kms_helper_common.c b/drivers/gpu/drm/drm_kms_helper_common.c
index 6e35a56a6102..6130199a83b6 100644
--- a/drivers/gpu/drm/drm_kms_helper_common.c
+++ b/drivers/gpu/drm/drm_kms_helper_common.c
@@ -26,6 +26,7 @@
  */
 
 #include <linux/module.h>
+#include <drm/drmP.h>
 
 #include "drm_crtc_helper_internal.h"
 
@@ -33,10 +34,28 @@ MODULE_AUTHOR("David Airlie, Jesse Barnes");
 MODULE_DESCRIPTION("DRM KMS helper");
 MODULE_LICENSE("GPL and additional rights");
 
+#if IS_ENABLED(CONFIG_DRM_LOAD_EDID_FIRMWARE)
+static char edid_firmware[PATH_MAX];
+module_param_string(edid_firmware, edid_firmware, sizeof(edid_firmware), 0444);
+MODULE_PARM_DESC(edid_firmware, "DEPRECATED. Use drm.edid_firmware instead.");
+static inline void legacy_set_edid_firmare_path(void)
+{
+	if (edid_firmware[0]) {
+		DRM_NOTE("drm_kms_firmware.edid_firmware is deprecated, "
+			 "please use drm.edid_firmware intead.\n");
+		__drm_set_edid_firmware_path(edid_firmware);
+	}
+}
+#else
+static inline void legacy_set_edid_firmare_path(void) {}
+#endif
+
 static int __init drm_kms_helper_init(void)
 {
 	int ret;
 
+	legacy_set_edid_firmare_path();
+
 	/* Call init functions from specific kms helpers here */
 	ret = drm_fb_helper_modinit();
 	if (ret < 0)
diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
index 1e1908a6b1d6..cdfb793255f0 100644
--- a/include/drm/drm_edid.h
+++ b/include/drm/drm_edid.h
@@ -341,12 +341,14 @@ int drm_av_sync_delay(struct drm_connector *connector,
 
 #ifdef CONFIG_DRM_LOAD_EDID_FIRMWARE
 struct edid *drm_load_edid_firmware(struct drm_connector *connector);
+void __drm_set_edid_firmware_path(const char *path);
 #else
 static inline struct edid *
 drm_load_edid_firmware(struct drm_connector *connector)
 {
 	return ERR_PTR(-ENOENT);
 }
+static inline void __drm_set_edid_firmware_path(const char *path) {}
 #endif
 
 int
-- 
2.11.0