1 files changed, 80 insertions, 0 deletions
diff --git a/drivers/gpu/drm/udl/udl_edid.c b/drivers/gpu/drm/udl/udl_edid.c
new file mode 100644
index 000000000000..d67e6bf1f2ae
--- /dev/null
+++ b/drivers/gpu/drm/udl/udl_edid.c
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/string.h>
+
+#include <drm/drm_drv.h>
+#include <drm/drm_edid.h>
+
+#include "udl_drv.h"
+#include "udl_edid.h"
+
+static int udl_read_edid_block(void *data, u8 *buf, unsigned int block, size_t len)
+{
+	struct udl_device *udl = data;
+	struct drm_device *dev = &udl->drm;
+	struct usb_device *udev = udl_to_usb_device(udl);
+	u8 *read_buff;
+	int idx, ret;
+	size_t i;
+
+	read_buff = kmalloc(2, GFP_KERNEL);
+	if (!read_buff)
+		return -ENOMEM;
+
+	if (!drm_dev_enter(dev, &idx)) {
+		ret = -ENODEV;
+		goto err_kfree;
+	}
+
+	for (i = 0; i < len; i++) {
+		int bval = (i + block * EDID_LENGTH) << 8;
+
+		ret = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
+				      0x02, (0x80 | (0x02 << 5)), bval,
+				      0xA1, read_buff, 2, USB_CTRL_GET_TIMEOUT);
+		if (ret < 0) {
+			drm_err(dev, "Read EDID byte %zu failed err %x\n", i, ret);
+			goto err_drm_dev_exit;
+		} else if (ret < 1) {
+			ret = -EIO;
+			drm_err(dev, "Read EDID byte %zu failed\n", i);
+			goto err_drm_dev_exit;
+		}
+
+		buf[i] = read_buff[1];
+	}
+
+	drm_dev_exit(idx);
+	kfree(read_buff);
+
+	return 0;
+
+err_drm_dev_exit:
+	drm_dev_exit(idx);
+err_kfree:
+	kfree(read_buff);
+	return ret;
+}
+
+bool udl_probe_edid(struct udl_device *udl)
+{
+	u8 hdr[8];
+	int ret;
+
+	ret = udl_read_edid_block(udl, hdr, 0, sizeof(hdr));
+	if (ret)
+		return false;
+
+	/*
+	 * The adapter sends all-zeros if no monitor has been
+	 * connected. We consider anything else a connection.
+	 */
+	return !!memchr_inv(hdr, 0, sizeof(hdr));
+}
+
+const struct drm_edid *udl_edid_read(struct drm_connector *connector)
+{
+	struct udl_device *udl = to_udl(connector->dev);
+
+	return drm_edid_read_custom(connector, udl_read_edid_block, udl);
+}