drm/udl: Reading all edid blocks in DRM/UDL driver

Now DRM/UDL driver retreives all edid data blocks instead of only base one.
Previous approch could lead to improper initialization of video mode with
certain monitors.
Signed-off-by: Robert Tarasov <tutankhamen@chromium.org>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171013001350.172155-2-tutankhamen@chromium.org

drivers/gpu/drm/udl/udl_connector.c

@@ -17,42 +17,79 @@
 #include "udl_connector.h"
 #include "udl_drv.h"
 
-/* dummy connector to just get EDID,
-   all UDL appear to have a DVI-D */
-
-static u8 *udl_get_edid(struct udl_device *udl)
+static bool udl_get_edid_block(struct udl_device *udl, int block_idx,
+							   u8 *buff)
 {
-	u8 *block;
-	char *rbuf;
 	int ret, i;
+	u8 *read_buff;
 
-	block = kmalloc(EDID_LENGTH, GFP_KERNEL);
-	if (block == NULL)
-		return NULL;
-
-	rbuf = kmalloc(2, GFP_KERNEL);
-	if (rbuf == NULL)
-		goto error;
+	read_buff = kmalloc(2, GFP_KERNEL);
+	if (!read_buff)
+		return false;
 
 	for (i = 0; i < EDID_LENGTH; i++) {
+		int bval = (i + block_idx * EDID_LENGTH) << 8;
 		ret = usb_control_msg(udl->udev,
-				      usb_rcvctrlpipe(udl->udev, 0), (0x02),
-				      (0x80 | (0x02 << 5)), i << 8, 0xA1, rbuf, 2,
-				      HZ);
+				      usb_rcvctrlpipe(udl->udev, 0),
+					  (0x02), (0x80 | (0x02 << 5)), bval,
+					  0xA1, read_buff, 2, HZ);
 		if (ret < 1) {
 			DRM_ERROR("Read EDID byte %d failed err %x\n", i, ret);
-			goto error;
+			kfree(read_buff);
+			return false;
 		}
-		block[i] = rbuf[1];
+		buff[i] = read_buff[1];
 	}
 
-	kfree(rbuf);
-	return block;
+	kfree(read_buff);
+	return true;
+}
 
-error:
-	kfree(block);
-	kfree(rbuf);
-	return NULL;
+static bool udl_get_edid(struct udl_device *udl, u8 **result_buff,
+			 int *result_buff_size)
+{
+	int i, extensions;
+	u8 *block_buff = NULL, *buff_ptr;
+
+	block_buff = kmalloc(EDID_LENGTH, GFP_KERNEL);
+	if (block_buff == NULL)
+		return false;
+
+	if (udl_get_edid_block(udl, 0, block_buff) &&
+	    memchr_inv(block_buff, 0, EDID_LENGTH)) {
+		extensions = ((struct edid *)block_buff)->extensions;
+		if (extensions > 0) {
+			/* we have to read all extensions one by one */
+			*result_buff_size = EDID_LENGTH * (extensions + 1);
+			*result_buff = kmalloc(*result_buff_size, GFP_KERNEL);
+			buff_ptr = *result_buff;
+			if (buff_ptr == NULL) {
+				kfree(block_buff);
+				return false;
+			}
+			memcpy(buff_ptr, block_buff, EDID_LENGTH);
+			kfree(block_buff);
+			buff_ptr += EDID_LENGTH;
+			for (i = 1; i < extensions; ++i) {
+				if (udl_get_edid_block(udl, i, buff_ptr)) {
+					buff_ptr += EDID_LENGTH;
+				} else {
+					kfree(*result_buff);
+					*result_buff = NULL;
+					return false;
+				}
+			}
+			return true;
+		}
+		/* we have only base edid block */
+		*result_buff = block_buff;
+		*result_buff_size = EDID_LENGTH;
+		return true;
+	}
+
+	kfree(block_buff);
+
+	return false;
 }
 
 static int udl_get_modes(struct drm_connector *connector)
@@ -84,33 +121,26 @@ static int udl_mode_valid(struct drm_connector *connector,
 static enum drm_connector_status
 udl_detect(struct drm_connector *connector, bool force)
 {
-	struct edid *edid;
+	u8 *edid_buff = NULL;
+	int edid_buff_size = 0;
 	struct udl_device *udl = connector->dev->dev_private;
 	struct udl_drm_connector *udl_connector =
 					container_of(connector,
 					struct udl_drm_connector,
 					connector);
 
+	/* cleanup previous edid */
 	if (udl_connector->edid != NULL) {
 		kfree(udl_connector->edid);
 		udl_connector->edid = NULL;
 	}
 
-	edid = (struct edid *)udl_get_edid(udl);
-	if (!edid || !memchr_inv(edid, 0, EDID_LENGTH))
-		return connector_status_disconnected;
 
-	udl_connector->edid = edid;
-
-	/*
-	 * We only read the main block, but if the monitor reports extension
-	 * blocks then the drm edid code expects them to be present, so patch
-	 * the extension count to 0.
-	 */
-	udl_connector->edid->checksum +=
-			udl_connector->edid->extensions;
-	udl_connector->edid->extensions = 0;
+	if (!udl_get_edid(udl, &edid_buff, &edid_buff_size))
+		return connector_status_disconnected;
 
+	udl_connector->edid = (struct edid *)edid_buff;
+	
 	return connector_status_connected;
 }