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@@ -0,0 +1,223 @@
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+/*
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+ * Copyright (C) 2015-2016 Free Electrons
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+ * Copyright (C) 2015-2016 NextThing Co
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+ *
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+ * Maxime Ripard <maxime.ripard@free-electrons.com>
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+ *
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+ * This program is free software; you can redistribute it and/or
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+ * modify it under the terms of the GNU General Public License as
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+ * published by the Free Software Foundation; either version 2 of
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+ * the License, or (at your option) any later version.
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+ */
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+
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+#include <linux/module.h>
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+#include <linux/of_graph.h>
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+
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+#include <drm/drmP.h>
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+#include <drm/drm_atomic_helper.h>
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+#include <drm/drm_crtc.h>
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+#include <drm/drm_crtc_helper.h>
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+
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+struct dumb_vga {
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+ struct drm_bridge bridge;
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+ struct drm_connector connector;
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+
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+ struct i2c_adapter *ddc;
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+};
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+
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+static inline struct dumb_vga *
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+drm_bridge_to_dumb_vga(struct drm_bridge *bridge)
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+{
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+ return container_of(bridge, struct dumb_vga, bridge);
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+}
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+
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+static inline struct dumb_vga *
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+drm_connector_to_dumb_vga(struct drm_connector *connector)
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+{
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+ return container_of(connector, struct dumb_vga, connector);
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+}
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+
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+static int dumb_vga_get_modes(struct drm_connector *connector)
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+{
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+ struct dumb_vga *vga = drm_connector_to_dumb_vga(connector);
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+ struct edid *edid;
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+ int ret;
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+
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+ if (IS_ERR(vga->ddc))
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+ goto fallback;
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+
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+ edid = drm_get_edid(connector, vga->ddc);
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+ if (!edid) {
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+ DRM_INFO("EDID readout failed, falling back to standard modes\n");
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+ goto fallback;
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+ }
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+
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+ drm_mode_connector_update_edid_property(connector, edid);
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+ return drm_add_edid_modes(connector, edid);
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+
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+fallback:
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+ /*
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+ * In case we cannot retrieve the EDIDs (broken or missing i2c
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+ * bus), fallback on the XGA standards
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+ */
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+ ret = drm_add_modes_noedid(connector, 1920, 1200);
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+
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+ /* And prefer a mode pretty much anyone can handle */
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+ drm_set_preferred_mode(connector, 1024, 768);
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+
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+ return ret;
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+}
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+
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+static const struct drm_connector_helper_funcs dumb_vga_con_helper_funcs = {
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+ .get_modes = dumb_vga_get_modes,
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+};
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+
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+static enum drm_connector_status
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+dumb_vga_connector_detect(struct drm_connector *connector, bool force)
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+{
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+ struct dumb_vga *vga = drm_connector_to_dumb_vga(connector);
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+
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+ /*
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+ * Even if we have an I2C bus, we can't assume that the cable
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+ * is disconnected if drm_probe_ddc fails. Some cables don't
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+ * wire the DDC pins, or the I2C bus might not be working at
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+ * all.
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+ */
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+ if (!IS_ERR(vga->ddc) && drm_probe_ddc(vga->ddc))
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+ return connector_status_connected;
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+
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+ return connector_status_unknown;
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+}
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+
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+static const struct drm_connector_funcs dumb_vga_con_funcs = {
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+ .dpms = drm_atomic_helper_connector_dpms,
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+ .detect = dumb_vga_connector_detect,
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+ .fill_modes = drm_helper_probe_single_connector_modes,
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+ .destroy = drm_connector_cleanup,
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+ .reset = drm_atomic_helper_connector_reset,
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+ .atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
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+ .atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
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+};
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+
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+static int dumb_vga_attach(struct drm_bridge *bridge)
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+{
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+ struct dumb_vga *vga = drm_bridge_to_dumb_vga(bridge);
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+ int ret;
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+
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+ if (!bridge->encoder) {
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+ DRM_ERROR("Missing encoder\n");
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+ return -ENODEV;
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+ }
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+
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+ drm_connector_helper_add(&vga->connector,
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+ &dumb_vga_con_helper_funcs);
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+ ret = drm_connector_init(bridge->dev, &vga->connector,
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+ &dumb_vga_con_funcs, DRM_MODE_CONNECTOR_VGA);
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+ if (ret) {
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+ DRM_ERROR("Failed to initialize connector\n");
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+ return ret;
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+ }
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+
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+ drm_mode_connector_attach_encoder(&vga->connector,
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+ bridge->encoder);
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+
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+ return 0;
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+}
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+
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+static const struct drm_bridge_funcs dumb_vga_bridge_funcs = {
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+ .attach = dumb_vga_attach,
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+};
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+
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+static struct i2c_adapter *dumb_vga_retrieve_ddc(struct device *dev)
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+{
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+ struct device_node *end_node, *phandle, *remote;
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+ struct i2c_adapter *ddc;
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+
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+ end_node = of_graph_get_endpoint_by_regs(dev->of_node, 1, -1);
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+ if (!end_node) {
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+ dev_err(dev, "Missing connector endpoint\n");
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+ return ERR_PTR(-ENODEV);
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+ }
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+
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+ remote = of_graph_get_remote_port_parent(end_node);
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+ of_node_put(end_node);
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+ if (!remote) {
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+ dev_err(dev, "Enable to parse remote node\n");
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+ return ERR_PTR(-EINVAL);
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+ }
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+
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+ phandle = of_parse_phandle(remote, "ddc-i2c-bus", 0);
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+ of_node_put(remote);
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+ if (!phandle)
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+ return ERR_PTR(-ENODEV);
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+
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+ ddc = of_get_i2c_adapter_by_node(phandle);
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+ of_node_put(phandle);
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+ if (!ddc)
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+ return ERR_PTR(-EPROBE_DEFER);
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+
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+ return ddc;
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+}
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+
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+static int dumb_vga_probe(struct platform_device *pdev)
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+{
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+ struct dumb_vga *vga;
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+ int ret;
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+
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+ vga = devm_kzalloc(&pdev->dev, sizeof(*vga), GFP_KERNEL);
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+ if (!vga)
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+ return -ENOMEM;
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+ platform_set_drvdata(pdev, vga);
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+
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+ vga->ddc = dumb_vga_retrieve_ddc(&pdev->dev);
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+ if (IS_ERR(vga->ddc)) {
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+ if (PTR_ERR(vga->ddc) == -ENODEV) {
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+ dev_dbg(&pdev->dev,
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+ "No i2c bus specified. Disabling EDID readout\n");
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+ } else {
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+ dev_err(&pdev->dev, "Couldn't retrieve i2c bus\n");
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+ return PTR_ERR(vga->ddc);
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+ }
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+ }
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+
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+ vga->bridge.funcs = &dumb_vga_bridge_funcs;
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+ vga->bridge.of_node = pdev->dev.of_node;
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+
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+ ret = drm_bridge_add(&vga->bridge);
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+ if (ret && !IS_ERR(vga->ddc))
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+ i2c_put_adapter(vga->ddc);
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+
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+ return ret;
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+}
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+
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+static int dumb_vga_remove(struct platform_device *pdev)
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+{
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+ struct dumb_vga *vga = platform_get_drvdata(pdev);
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+
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+ drm_bridge_remove(&vga->bridge);
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+
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+ if (!IS_ERR(vga->ddc))
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+ i2c_put_adapter(vga->ddc);
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+
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+ return 0;
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+}
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+
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+static const struct of_device_id dumb_vga_match[] = {
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+ { .compatible = "dumb-vga-dac" },
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+ {},
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+};
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+MODULE_DEVICE_TABLE(of, dumb_vga_match);
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+
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+static struct platform_driver dumb_vga_driver = {
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+ .probe = dumb_vga_probe,
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+ .remove = dumb_vga_remove,
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+ .driver = {
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+ .name = "dumb-vga-dac",
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+ .of_match_table = dumb_vga_match,
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+ },
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+};
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+module_platform_driver(dumb_vga_driver);
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+
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+MODULE_AUTHOR("Maxime Ripard <maxime.ripard@free-electrons.com>");
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+MODULE_DESCRIPTION("Dumb VGA DAC bridge driver");
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+MODULE_LICENSE("GPL");
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