drm: Try loading builtin EDIDs first

If the firmware is not builtin and userspace is not yet running, we can
stall the boot process for a minute whilst the firmware loader times
out. This is contrary to expectations of providing a builtin EDID!

In the process, we can rearrange the code to make the error handling
more resilient and prevent gcc warning about unitialised variables along
the error paths.

v2: Load builtins first, fix gcc second (Jani) and cosmetics (Ville).
v3: Verify that we do not read beyond the end of the fwdata (Ville)

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_edid_load.c

@@ -32,7 +32,7 @@ MODULE_PARM_DESC(edid_firmware, "Do not probe monitor, use specified EDID blob "
 	"from built-in data or /lib/firmware instead. ");
 
 #define GENERIC_EDIDS 5
-static char *generic_edid_name[GENERIC_EDIDS] = {
+static const char *generic_edid_name[GENERIC_EDIDS] = {
 	"edid/1024x768.bin",
 	"edid/1280x1024.bin",
 	"edid/1600x1200.bin",
@@ -40,7 +40,7 @@ static char *generic_edid_name[GENERIC_EDIDS] = {
 	"edid/1920x1080.bin",
 };
 
-static u8 generic_edid[GENERIC_EDIDS][128] = {
+static const u8 generic_edid[GENERIC_EDIDS][128] = {
 	{
 	0x00, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00,
 	0x31, 0xd8, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
@@ -133,63 +133,68 @@ static u8 generic_edid[GENERIC_EDIDS][128] = {
 	},
 };
 
+static int edid_size(const u8 *edid, int data_size)
+{
+	if (data_size < EDID_LENGTH)
+		return 0;
+
+	return (edid[0x7e] + 1) * EDID_LENGTH;
+}
+
 static u8 *edid_load(struct drm_connector *connector, const char *name,
 			const char *connector_name)
 {
-	const struct firmware *fw;
-	struct platform_device *pdev;
-	u8 *fwdata = NULL, *edid, *new_edid;
-	int fwsize, expected;
-	int builtin = 0, err = 0;
+	const struct firmware *fw = NULL;
+	const u8 *fwdata;
+	u8 *edid;
+	int fwsize, builtin;
 	int i, valid_extensions = 0;
 	bool print_bad_edid = !connector->bad_edid_counter || (drm_debug & DRM_UT_KMS);
 
-	pdev = platform_device_register_simple(connector_name, -1, NULL, 0);
-	if (IS_ERR(pdev)) {
-		DRM_ERROR("Failed to register EDID firmware platform device "
-		    "for connector \"%s\"\n", connector_name);
-		err = -EINVAL;
-		goto out;
-	}
-
-	err = request_firmware(&fw, name, &pdev->dev);
-	platform_device_unregister(pdev);
-
-	if (err) {
-		i = 0;
-		while (i < GENERIC_EDIDS && strcmp(name, generic_edid_name[i]))
-			i++;
-		if (i < GENERIC_EDIDS) {
-			err = 0;
-			builtin = 1;
+	builtin = 0;
+	for (i = 0; i < GENERIC_EDIDS; i++) {
+		if (strcmp(name, generic_edid_name[i]) == 0) {
 			fwdata = generic_edid[i];
 			fwsize = sizeof(generic_edid[i]);
+			builtin = 1;
+			break;
 		}
 	}
+	if (!builtin) {
+		struct platform_device *pdev;
+		int err;
 
-	if (err) {
-		DRM_ERROR("Requesting EDID firmware \"%s\" failed (err=%d)\n",
-		    name, err);
-		goto out;
-	}
+		pdev = platform_device_register_simple(connector_name, -1, NULL, 0);
+		if (IS_ERR(pdev)) {
+			DRM_ERROR("Failed to register EDID firmware platform device "
+				  "for connector \"%s\"\n", connector_name);
+			return ERR_CAST(pdev);
+		}
+
+		err = request_firmware(&fw, name, &pdev->dev);
+		platform_device_unregister(pdev);
+		if (err) {
+			DRM_ERROR("Requesting EDID firmware \"%s\" failed (err=%d)\n",
+				  name, err);
+			return ERR_PTR(err);
+		}
 
-	if (fwdata == NULL) {
-		fwdata = (u8 *) fw->data;
+		fwdata = fw->data;
 		fwsize = fw->size;
 	}
 
-	expected = (fwdata[0x7e] + 1) * EDID_LENGTH;
-	if (expected != fwsize) {
+	if (edid_size(fwdata, fwsize) != fwsize) {
 		DRM_ERROR("Size of EDID firmware \"%s\" is invalid "
-		    "(expected %d, got %d)\n", name, expected, (int) fwsize);
-		err = -EINVAL;
-		goto relfw_out;
+			  "(expected %d, got %d\n", name,
+			  edid_size(fwdata, fwsize), (int)fwsize);
+		edid = ERR_PTR(-EINVAL);
+		goto out;
 	}
 
 	edid = kmemdup(fwdata, fwsize, GFP_KERNEL);
 	if (edid == NULL) {
-		err = -ENOMEM;
-		goto relfw_out;
+		edid = ERR_PTR(-ENOMEM);
+		goto out;
 	}
 
 	if (!drm_edid_block_valid(edid, 0, print_bad_edid)) {
@@ -197,8 +202,8 @@ static u8 *edid_load(struct drm_connector *connector, const char *name,
 		DRM_ERROR("Base block of EDID firmware \"%s\" is invalid ",
 		    name);
 		kfree(edid);
-		err = -EINVAL;
-		goto relfw_out;
+		edid = ERR_PTR(-EINVAL);
+		goto out;
 	}
 
 	for (i = 1; i <= edid[0x7e]; i++) {
@@ -210,19 +215,18 @@ static u8 *edid_load(struct drm_connector *connector, const char *name,
 	}
 
 	if (valid_extensions != edid[0x7e]) {
+		u8 *new_edid;
+
 		edid[EDID_LENGTH-1] += edid[0x7e] - valid_extensions;
 		DRM_INFO("Found %d valid extensions instead of %d in EDID data "
 		    "\"%s\" for connector \"%s\"\n", valid_extensions,
 		    edid[0x7e], name, connector_name);
 		edid[0x7e] = valid_extensions;
+
 		new_edid = krealloc(edid, (valid_extensions + 1) * EDID_LENGTH,
-		    GFP_KERNEL);
-		if (new_edid == NULL) {
-			err = -ENOMEM;
-			kfree(edid);
-			goto relfw_out;
-		}
-		edid = new_edid;
+				    GFP_KERNEL);
+		if (new_edid)
+			edid = new_edid;
 	}
 
 	DRM_INFO("Got %s EDID base block and %d extension%s from "
@@ -230,13 +234,9 @@ static u8 *edid_load(struct drm_connector *connector, const char *name,
 	    "external", valid_extensions, valid_extensions == 1 ? "" : "s",
 	    name, connector_name);
 
-relfw_out:
-	release_firmware(fw);
-
 out:
-	if (err)
-		return ERR_PTR(err);
-
+	if (fw)
+		release_firmware(fw);
 	return edid;
 }