[RFC v4 25/25] drm/client: Hack: Add DRM VT console client

["Noralf Trønnes" <noralf@tronnes.org>]

A hack to test the client API.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
---
 drivers/gpu/drm/Makefile           |   1 +
 drivers/gpu/drm/client/Kconfig     |   5 +
 drivers/gpu/drm/client/Makefile    |   3 +
 drivers/gpu/drm/client/drm_vtcon.c | 785 +++++++++++++++++++++++++++++++++++++
 4 files changed, 794 insertions(+)
 create mode 100644 drivers/gpu/drm/client/Makefile
 create mode 100644 drivers/gpu/drm/client/drm_vtcon.c

diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 388527093f80..ea63eb9e93ec 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -47,6 +47,7 @@ obj-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o
 obj-$(CONFIG_DRM_DEBUG_MM_SELFTEST) += selftests/
 
 obj-$(CONFIG_DRM)	+= drm.o
+obj-y			+= client/
 obj-$(CONFIG_DRM_MIPI_DSI) += drm_mipi_dsi.o
 obj-$(CONFIG_DRM_PANEL_ORIENTATION_QUIRKS) += drm_panel_orientation_quirks.o
 obj-$(CONFIG_DRM_ARM)	+= arm/
diff --git a/drivers/gpu/drm/client/Kconfig b/drivers/gpu/drm/client/Kconfig
index 6b01f2e51fb3..b03f3baf8b3f 100644
--- a/drivers/gpu/drm/client/Kconfig
+++ b/drivers/gpu/drm/client/Kconfig
@@ -6,4 +6,9 @@ config DRM_CLIENT_BOOTSPLASH
 	help
 	  DRM Bootsplash
 
+config DRM_CLIENT_VTCON
+	tristate "DRM VT console"
+	help
+	  DRM VT console
+
 endmenu
diff --git a/drivers/gpu/drm/client/Makefile b/drivers/gpu/drm/client/Makefile
new file mode 100644
index 000000000000..7d39f1bc2b68
--- /dev/null
+++ b/drivers/gpu/drm/client/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_DRM_CLIENT_VTCON) += drm_vtcon.o
diff --git a/drivers/gpu/drm/client/drm_vtcon.c b/drivers/gpu/drm/client/drm_vtcon.c
new file mode 100644
index 000000000000..910b4ec1a686
--- /dev/null
+++ b/drivers/gpu/drm/client/drm_vtcon.c
@@ -0,0 +1,785 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright 2018 Noralf Trønnes
+
+#include <linux/console.h>
+#include <linux/font.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/vt_buffer.h>
+#include <linux/vt_kern.h>
+#include <linux/workqueue.h>
+
+#include <drm/drm_client.h>
+#include <drm/drm_drv.h>
+#include <drm/drm_fourcc.h>
+#include <drm/drm_modes.h>
+#include <drm/drm_print.h>
+
+/* TODO: Scrolling */
+
+/*
+ * The code consists of 3 parts:
+ *
+ * 1. The DRM client
+ *    Gets a display, uses the first mode to find a font,
+ *    sets the max cols/rows and a matching text buffer.
+ *
+ * 2. The VT console
+ *    Writes to the text buffer which consists of CGA colored characters.
+ *    Schedules the worker when it needs rendering or blanking.
+ *
+ * 3. Worker
+ *    Does modesetting, blanking and rendering.
+ *    It takes a snapshot of the VT text buffer and renders the changes since
+ *    last.
+ */
+
+struct drm_vtcon_vc {
+	struct mutex lock;
+
+	u16 *text_buf;
+	size_t buf_len;
+
+	unsigned int rows;
+	unsigned int cols;
+	unsigned int max_rows;
+	unsigned int max_cols;
+	const struct font_desc *font;
+	bool blank;
+	unsigned long cursor_blink_jiffies;
+};
+
+static struct drm_vtcon_vc *drm_vtcon_vc;
+
+struct drm_vtcon {
+	struct drm_client_dev *client;
+	struct drm_client_display *display;
+	struct drm_client_buffer *buffer;
+
+	unsigned int rows;
+	unsigned int cols;
+
+	u16 *text_buf[2];
+	size_t buf_len;
+	unsigned int buf_idx;
+	bool blank;
+};
+
+static struct drm_vtcon *vtcon_instance;
+
+static int drm_vtcon_dev_id;
+module_param_named(dev, drm_vtcon_dev_id, int, 0600);
+MODULE_PARM_DESC(drm_vtcon_dev_id, "DRM device id [default=0]");
+
+#define drm_vtcon_debug(vc, fmt, ...) \
+	pr_debug("%s[%u]: " fmt, __func__, vc->vc_num, ##__VA_ARGS__)
+
+/* CGA color palette: 4-bit RGBI: intense red green blue */
+static const u32 drm_vtcon_paletteX888[16] = {
+	0x00000000, /*  0 black */
+	0x000000aa, /*  1 blue */
+	0x0000aa00, /*  2 green */
+	0x0000aaaa, /*  3 cyan */
+	0x00aa0000, /*  4 red */
+	0x00aa00aa, /*  5 magenta */
+	0x00aa5500, /*  6 brown */
+	0x00aaaaaa, /*  7 light gray */
+	0x00555555, /*  8 dark gray */
+	0x005555ff, /*  9 bright blue */
+	0x0055ff55, /* 10 bright green */
+	0x0055ffff, /* 11 bright cyan */
+	0x00ff5555, /* 12 bright red */
+	0x00ff55ff, /* 13 bright magenta */
+	0x00ffff55, /* 14 yellow */
+	0x00ffffff  /* 15 white */
+};
+
+static void
+drm_vtcon_render_char(struct drm_vtcon *vtcon, unsigned int x, unsigned int y,
+		      u16 cc, const struct font_desc *font)
+{
+	struct drm_client_buffer *buffer = vtcon->buffer;
+	unsigned int h, w;
+	const u8 *src;
+	void *dst;
+	u32 *pix;
+	u32 fg_col = drm_vtcon_paletteX888[(cc & 0x0f00) >> 8];
+	u32 bg_col = drm_vtcon_paletteX888[cc >> 12];
+
+	src = font->data + (cc & 0xff) * font->height;
+	dst = vtcon->buffer->vaddr + y * buffer->pitch + x * sizeof(u32);
+
+	for (h = 0; h < font->height; h++) {
+		u8 fontline = *(src + h);
+
+		pix = dst;
+		for (w = 0; w < font->width; w++)
+			pix[w] = fontline & BIT(7 - w) ? fg_col : bg_col;
+		dst += buffer->pitch;
+	}
+}
+
+static int drm_vtcon_modeset(struct drm_vtcon *vtcon, unsigned int cols,
+			     unsigned int rows, const struct font_desc *font)
+{
+	struct drm_client_display *display = vtcon->display;
+	struct drm_client_dev *client = vtcon->client;
+	struct drm_display_mode *mode, *best_mode = NULL;
+	unsigned int best_cols = ~0, best_rows = ~0;
+	struct drm_client_buffer *buffer;
+	int ret;
+
+	DRM_DEV_INFO(client->dev->dev, "IN %ux%u\n", cols, rows);
+
+	/* Find the smallest mode that fits */
+	drm_client_display_for_each_mode(mode, display) {
+		unsigned int mode_cols = mode->hdisplay / font->width;
+		unsigned int mode_rows = mode->vdisplay / font->height;
+
+		DRM_DEV_INFO(client->dev->dev,
+			     "try: %ux%u\n", mode_cols, mode_rows);
+
+		if (mode_cols < cols || mode_rows < rows)
+			break;
+
+		if (mode_cols >= best_cols || mode_rows >= best_rows)
+			continue;
+
+		best_cols = mode_cols;
+		best_rows = mode_rows;
+		best_mode = mode;
+	}
+
+	if (!best_mode) {
+		DRM_DEV_INFO(client->dev->dev, "Couldn't find mode for %ux%u\n", cols, rows);
+		return -EINVAL;
+	}
+
+	DRM_DEV_INFO(client->dev->dev, "Chosen: %ux%u\n", best_cols, best_rows);
+
+	buffer = drm_client_framebuffer_create(client, best_mode, DRM_FORMAT_XRGB8888);
+	if (IS_ERR(buffer)) {
+		ret = PTR_ERR(buffer);
+		DRM_DEV_ERROR(client->dev->dev,
+			      "Failed to create framebuffer: %d\n", ret);
+		return ret;
+	}
+
+	ret = drm_client_display_commit(display, buffer->fb, best_mode);
+	if (ret) {
+		DRM_DEV_ERROR(client->dev->dev,
+			      "Failed to commit mode: %d\n", ret);
+		goto err_free_buffer;
+	}
+
+	drm_client_framebuffer_delete(vtcon->buffer);
+
+	vtcon->buffer = buffer;
+	vtcon->cols = cols;
+	vtcon->rows = rows;
+
+	DRM_DEV_INFO(client->dev->dev, "OUT\n");
+
+	return 0;
+
+err_free_buffer:
+	drm_client_framebuffer_delete(buffer);
+
+	DRM_DEV_INFO(client->dev->dev, "OUT ret=%d\n", ret);
+
+	return ret;
+}
+
+static void drm_vtcon_blank(struct drm_vtcon *vtcon, bool blank)
+{
+	int mode = blank ? DRM_MODE_DPMS_OFF : DRM_MODE_DPMS_ON;
+
+	drm_client_display_dpms(vtcon->display, mode);
+	vtcon->blank = blank;
+}
+
+static int drm_vtcon_resize_buf(struct drm_vtcon *vtcon, size_t len)
+{
+	u16 *text_buf[2];
+
+	text_buf[0] = kzalloc(len, GFP_KERNEL);
+	text_buf[1] = kzalloc(len, GFP_KERNEL);
+	if (!text_buf[0] || !text_buf[1]) {
+		kfree(text_buf[0]);
+		kfree(text_buf[1]);
+		return -ENOMEM;
+	}
+
+	kfree(vtcon->text_buf[0]);
+	kfree(vtcon->text_buf[1]);
+
+	vtcon->text_buf[0] = text_buf[0];
+	vtcon->text_buf[1] = text_buf[1];
+	vtcon->buf_len = len;
+
+	return 0;
+}
+
+static void drm_vtcon_work_fn(struct work_struct *work)
+{
+	struct drm_vtcon *vtcon = vtcon_instance;
+	unsigned int vc_cols, vc_rows, col, row, x, y;
+	const struct font_desc *font;
+	u16 prev, curr;
+	bool blank, render_all = false;
+	struct drm_clip_rect clip = {
+		.x1 = ~0,
+		.y1 = ~0,
+		.x2 = 0,
+		.y2 = 0,
+	};
+	char *str;
+	int ret;
+
+	if (!vtcon->display)
+		return;
+
+	mutex_lock(&drm_vtcon_vc->lock);
+
+	vc_cols = drm_vtcon_vc->cols;
+	vc_rows = drm_vtcon_vc->rows;
+	font = drm_vtcon_vc->font;
+	blank = drm_vtcon_vc->blank;
+
+	if (vtcon->buf_len != drm_vtcon_vc->buf_len) {
+		ret = drm_vtcon_resize_buf(vtcon, drm_vtcon_vc->buf_len);
+		if (ret) {
+			mutex_unlock(&drm_vtcon_vc->lock);
+			return;
+		}
+		render_all = true;
+	}
+
+	vtcon->buf_idx = !vtcon->buf_idx;
+	memcpy(vtcon->text_buf[vtcon->buf_idx], drm_vtcon_vc->text_buf,
+	       vc_cols * vc_rows * sizeof(u16));
+
+	mutex_unlock(&drm_vtcon_vc->lock);
+
+	if (vtcon->cols != vc_cols || vtcon->rows != vc_rows) {
+		ret = drm_vtcon_modeset(vtcon, vc_cols, vc_rows, font);
+		if (ret)
+			return;
+		render_all = true;
+	} else if (vtcon->blank != blank) {
+		drm_vtcon_blank(vtcon, blank);
+	}
+
+	str = kmalloc(vc_cols + 1, GFP_KERNEL);
+	if (!str)
+		return;
+
+	for (row = 0; row < vc_rows; row++) {
+		for (col = 0; col < vc_cols; col++) {
+			prev = vtcon->text_buf[!vtcon->buf_idx][col + (row * vc_cols)];
+			curr = vtcon->text_buf[vtcon->buf_idx][col + (row * vc_cols)];
+
+			if (render_all || prev != curr) {
+				str[col] = curr;
+				x = col * font->width;
+				y = row * font->height;
+
+				clip.x1 = min_t(u32, clip.x1, x);
+				clip.y1 = min_t(u32, clip.y1, y);
+				clip.x2 = max_t(u32, clip.x2, x + font->width);
+				clip.y2 = max_t(u32, clip.y2, y + font->height);
+
+				drm_vtcon_render_char(vtcon, x, y, curr, font);
+			} else {
+				str[col] = ' ';
+			}
+		}
+		str[vc_cols] = '\0';
+//		pr_info("%02u|%s\n", row, str);
+	}
+
+	kfree(str);
+
+	if (clip.x1 < clip.x2)
+		drm_client_framebuffer_flush(vtcon->buffer, &clip);
+}
+
+static DECLARE_WORK(drm_vtcon_work, drm_vtcon_work_fn);
+
+static const char *drm_vtcon_con_startup(void)
+{
+	return "drm-vt";
+}
+
+static void drm_vtcon_con_init(struct vc_data *vc, int init)
+{
+	drm_vtcon_debug(vc, "(init=%d) drm_vtcon_vc=%p\n", init, drm_vtcon_vc);
+
+	vc->vc_can_do_color = 1;
+
+	if (init) {
+		vc->vc_cols = drm_vtcon_vc->cols;
+		vc->vc_rows = drm_vtcon_vc->rows;
+	} else {
+		vc_resize(vc, drm_vtcon_vc->cols, drm_vtcon_vc->rows);
+	}
+}
+
+static void drm_vtcon_con_deinit(struct vc_data *vc)
+{
+	drm_vtcon_debug(vc, "\n");
+}
+
+static void drm_vtcon_con_putcs(struct vc_data *vc, const unsigned short *s,
+				int count, int y, int x)
+{
+	u16 *dest;
+
+	dest = &drm_vtcon_vc->text_buf[x + (y * drm_vtcon_vc->cols)];
+
+	for (; count > 0; count--)
+		scr_writew(scr_readw(s++), dest++);
+
+	schedule_work(&drm_vtcon_work);
+}
+
+static void drm_vtcon_con_putc(struct vc_data *vc, int ch, int y, int x)
+{
+	unsigned short chr;
+
+	scr_writew(ch, &chr);
+	drm_vtcon_con_putcs(vc, &chr, 1, y, x);
+}
+
+/* TODO: How do I actually test this? */
+static void drm_vtcon_con_clear(struct vc_data *vc, int y, int x,
+				int height, int width)
+{
+	drm_vtcon_debug(vc, "\n");
+
+	scr_memcpyw(drm_vtcon_vc->text_buf, (unsigned short *)vc->vc_pos,
+		    vc->vc_cols * vc->vc_rows);
+	schedule_work(&drm_vtcon_work);
+}
+
+static int drm_vtcon_con_switch(struct vc_data *vc)
+{
+	drm_vtcon_debug(vc, "%ux%u\n", vc->vc_cols, vc->vc_rows);
+
+	mutex_lock(&drm_vtcon_vc->lock);
+	drm_vtcon_vc->cols = vc->vc_cols;
+	drm_vtcon_vc->rows = vc->vc_rows;
+	mutex_unlock(&drm_vtcon_vc->lock);
+
+	return 1; /* redraw */
+}
+
+static int drm_vtcon_con_resize(struct vc_data *vc, unsigned int width,
+				unsigned int height, unsigned int user)
+{
+	int ret = 0;
+
+	drm_vtcon_debug(vc, "width=%u, height=%u, user=%u\n", width, height, user);
+
+	mutex_lock(&drm_vtcon_vc->lock);
+
+	if (width > drm_vtcon_vc->max_cols || height > drm_vtcon_vc->max_rows)
+		ret = -EINVAL;
+
+	mutex_unlock(&drm_vtcon_vc->lock);
+
+	drm_vtcon_debug(vc, "ret=%d\n", ret);
+
+	return ret;
+}
+
+static void drm_vtcon_con_set_palette(struct vc_data *vc,
+				      const unsigned char *table)
+{
+	drm_vtcon_debug(vc, "\n");
+}
+
+static int drm_vtcon_con_blank(struct vc_data *vc, int blank, int mode_switch)
+{
+	drm_vtcon_debug(vc, "(blank=%d, mode_switch=%d)\n", blank, mode_switch);
+
+	mutex_lock(&drm_vtcon_vc->lock);
+	drm_vtcon_vc->blank = blank;
+	mutex_unlock(&drm_vtcon_vc->lock);
+
+	schedule_work(&drm_vtcon_work);
+
+	return 0;
+}
+
+static void drm_vtcon_con_scrolldelta(struct vc_data *vc, int lines)
+{
+	drm_vtcon_debug(vc, "(lines=%d)\n", lines);
+}
+
+static void drm_vtcon_con_cursor_draw(bool show)
+{
+	static unsigned short set_chr, saved_chr;
+	static int prev_x, prev_y;
+	struct vc_data *vc = vc_cons[fg_console].d;
+	unsigned short *pos;
+
+	if (saved_chr) {
+		pos = &drm_vtcon_vc->text_buf[prev_x + (prev_y * drm_vtcon_vc->cols)];
+		if (*pos == set_chr)
+			*pos = saved_chr;
+		saved_chr = 0;
+	}
+
+	if (show) {
+		pos = &drm_vtcon_vc->text_buf[vc->vc_x + (vc->vc_y * drm_vtcon_vc->cols)];
+		*pos = scr_readw((u16 *)vc->vc_pos);
+		saved_chr = *pos;
+		set_chr = *pos & 0xff00;
+		set_chr |= '_';
+		*pos = set_chr;
+		prev_x = vc->vc_x;
+		prev_y = vc->vc_y;
+	}
+
+	schedule_work(&drm_vtcon_work);
+}
+
+static void drm_vtcon_con_cursor_timer_handler(struct timer_list *t)
+{
+	static bool show;
+
+	show = !show;
+	drm_vtcon_con_cursor_draw(show);
+	mod_timer(t, jiffies + drm_vtcon_vc->cursor_blink_jiffies);
+}
+
+static DEFINE_TIMER(drm_vtcon_con_cursor_timer, drm_vtcon_con_cursor_timer_handler);
+
+static void drm_vtcon_con_cursor(struct vc_data *vc, int mode)
+{
+	//drm_vtcon_debug(vc, "(mode=%d)\n", mode);
+
+	switch (mode) {
+	case CM_ERASE:
+		drm_vtcon_con_cursor_draw(false);
+		del_timer_sync(&drm_vtcon_con_cursor_timer);
+		break;
+	case CM_MOVE:
+	case CM_DRAW:
+		drm_vtcon_vc->cursor_blink_jiffies = msecs_to_jiffies(vc->vc_cur_blink_ms);
+		mod_timer(&drm_vtcon_con_cursor_timer,
+			  jiffies + drm_vtcon_vc->cursor_blink_jiffies);
+		break;
+	}
+}
+
+static bool drm_vtcon_con_scroll(struct vc_data *vc, unsigned int top,
+				 unsigned int bottom, enum con_scroll dir,
+				 unsigned int lines)
+{
+	size_t count;
+
+	switch (dir) {
+	case SM_UP:
+		count = vc->vc_cols * (vc->vc_rows - lines);
+		memmove(drm_vtcon_vc->text_buf, drm_vtcon_vc->text_buf + vc->vc_cols, count * sizeof(u16));
+		memset(drm_vtcon_vc->text_buf + count, 0, vc->vc_cols * lines * sizeof(u16));
+		break;
+	case SM_DOWN:
+		drm_vtcon_debug(vc, "TODO\n");
+		break;
+	}
+
+	return false;
+}
+
+static const struct consw drm_vtcon_consw = {
+	/* owner is not set, it blocks module unload */
+	.con_startup		= drm_vtcon_con_startup,
+	.con_init		= drm_vtcon_con_init,
+	.con_deinit		= drm_vtcon_con_deinit,
+	.con_clear		= drm_vtcon_con_clear,
+	.con_putc		= drm_vtcon_con_putc,
+	.con_putcs		= drm_vtcon_con_putcs,
+	.con_cursor		= drm_vtcon_con_cursor,
+	.con_scroll		= drm_vtcon_con_scroll,
+	.con_switch		= drm_vtcon_con_switch,
+	.con_blank		= drm_vtcon_con_blank,
+	.con_resize		= drm_vtcon_con_resize,
+	.con_set_palette	= drm_vtcon_con_set_palette,
+	.con_scrolldelta	= drm_vtcon_con_scrolldelta,
+};
+
+static int drm_vtcon_vc_set_max(struct drm_display_mode *mode)
+{
+	u16 *new_buf = NULL, *old_buf = NULL;
+	const struct font_desc *font;
+	unsigned int cols, rows, i;
+	size_t buf_len;
+
+	/* only 8 bit wide and 8 or 16-bit high */
+	font = get_default_font(mode->hdisplay, mode->vdisplay,
+				BIT(8 - 1), BIT(8 - 1) | BIT(16 - 1));
+	if (!font)
+		return -ENODEV;
+
+	pr_info("%s: font: %s\n", __func__, font->name);
+
+	cols = mode->hdisplay / font->width;
+	rows = mode->vdisplay / font->height;
+
+	pr_info("%s: ASKED: cols=%u, rows=%u\n", __func__, cols, rows);
+
+	if (drm_vtcon_vc->max_cols == cols && drm_vtcon_vc->max_rows == rows &&
+	    drm_vtcon_vc->font == font)
+		return 0;
+
+	buf_len = cols * rows * sizeof(u16);
+	if (buf_len > drm_vtcon_vc->buf_len) {
+		new_buf = kzalloc(buf_len, GFP_KERNEL);
+		if (!new_buf)
+			return -ENOMEM;
+	}
+
+	mutex_lock(&drm_vtcon_vc->lock);
+
+	if (new_buf) {
+		DRM_INFO("Allocated new buf: buf_len=%zu\n", buf_len);
+		old_buf = drm_vtcon_vc->text_buf;
+		drm_vtcon_vc->text_buf = new_buf;
+		drm_vtcon_vc->buf_len = buf_len;
+	}
+
+	drm_vtcon_vc->max_cols = cols;
+	drm_vtcon_vc->max_rows = rows;
+	drm_vtcon_vc->font = font;
+
+	mutex_unlock(&drm_vtcon_vc->lock);
+
+	pr_info("%s: max_cols=%u, max_rows=%u\n", __func__, drm_vtcon_vc->max_cols,
+		drm_vtcon_vc->max_rows);
+
+	console_lock();
+	for (i = 0; i < 2; i++)
+		vc_resize(vc_cons[i].d, drm_vtcon_vc->max_cols,
+			  drm_vtcon_vc->max_rows);
+	console_unlock();
+
+	kfree(old_buf);
+
+	return 0;
+}
+
+static int drm_vtcon_setup_dev(struct drm_vtcon *vtcon)
+{
+	struct drm_client_dev *client = vtcon->client;
+	struct drm_client_display *display;
+	struct drm_display_mode *mode;
+	int ret;
+
+	display = drm_client_find_display(client->dev, 0, 0);
+	if (IS_ERR(display))
+		return PTR_ERR(display);
+	if (!display)
+		return -ENOENT;
+
+	mode = display->mode;
+	if (!mode) {
+		ret = -EINVAL;
+		goto err_free_display;
+	}
+
+	ret = drm_vtcon_vc_set_max(mode);
+	if (ret)
+		goto err_free_display;
+
+	pr_info("%s: cols=%u, rows=%u\n", __func__, drm_vtcon_vc->cols, drm_vtcon_vc->rows);
+
+	vtcon->display = display;
+
+	schedule_work(&drm_vtcon_work);
+
+	return 0;
+
+err_free_display:
+	drm_client_display_free(display);
+
+	return ret;
+}
+
+static int drm_vtcon_client_hotplug(struct drm_client_dev *client)
+{
+	struct drm_vtcon *vtcon = client->private;
+	int ret = 0;
+
+	if (!vtcon->display)
+		ret = drm_vtcon_setup_dev(vtcon);
+
+	return ret;
+}
+
+static struct drm_client_dev *vtcon_client;
+static DEFINE_MUTEX(vtcon_client_lock);
+
+static int drm_vtcon_client_remove(struct drm_client_dev *client)
+{
+	struct drm_vtcon *vtcon = client->private;
+	struct drm_client_display *display = vtcon->display;
+
+	mutex_lock(&vtcon_client_lock);
+
+	vtcon_client = NULL;
+
+	if (!display)
+		goto out_unlock;
+
+	vtcon->display = NULL;
+	flush_work(&drm_vtcon_work);
+	kfree(vtcon->text_buf[0]);
+	kfree(vtcon->text_buf[1]);
+	drm_client_framebuffer_delete(vtcon->buffer);
+	vtcon->buffer = NULL;
+	drm_client_display_free(display);
+
+out_unlock:
+	mutex_unlock(&vtcon_client_lock);
+
+	return 0;
+}
+
+static const struct drm_client_funcs drm_vtcon_client_funcs = {
+	.name		= "vtcon",
+	.remove		= drm_vtcon_client_remove,
+	.hotplug	= drm_vtcon_client_hotplug,
+};
+
+static struct drm_client_dev *drm_vtcon_client_new(unsigned int dev_id)
+{
+	struct drm_vtcon *vtcon = vtcon_instance;
+	struct drm_client_dev *client;
+
+	if (vtcon->client)
+		return ERR_PTR(-EBUSY);
+
+	client = drm_client_new_from_id(dev_id, &drm_vtcon_client_funcs);
+	if (IS_ERR(client))
+		return client;
+
+	vtcon->client = client;
+	client->private = vtcon;
+
+	/*
+	 * vc4 isn't done with it's setup when drm_dev_register() is called.
+	 * It should have shouldn't it?
+	 * So to keep it from crashing defer setup to hotplug...
+	 */
+	if (client->dev->mode_config.max_width)
+		drm_vtcon_client_hotplug(client);
+
+	return 0;
+}
+
+static void drm_vtcon_teardown(void)
+{
+	struct drm_vtcon *vtcon = vtcon_instance;
+
+	if (!drm_vtcon_vc)
+		return;
+
+	kfree(drm_vtcon_vc->text_buf);
+	mutex_destroy(&drm_vtcon_vc->lock);
+	kfree(drm_vtcon_vc);
+	kfree(vtcon);
+}
+
+static int __init drm_vtcon_setup(void)
+{
+	struct drm_vtcon *vtcon;
+
+	drm_vtcon_vc = kzalloc(sizeof(*drm_vtcon_vc), GFP_KERNEL);
+	vtcon = kzalloc(sizeof(*vtcon), GFP_KERNEL);
+	if (!drm_vtcon_vc || !vtcon)
+		goto err_free;
+
+	drm_vtcon_vc->max_cols = 80;
+	drm_vtcon_vc->max_rows = 25;
+	drm_vtcon_vc->cols = drm_vtcon_vc->max_cols;
+	drm_vtcon_vc->rows = drm_vtcon_vc->max_rows;
+	pr_info("%s: cols=%u, rows=%u\n", __func__, drm_vtcon_vc->cols, drm_vtcon_vc->rows);
+
+	drm_vtcon_vc->buf_len = drm_vtcon_vc->max_cols * drm_vtcon_vc->max_rows * sizeof(u16);
+	drm_vtcon_vc->text_buf = kzalloc(drm_vtcon_vc->buf_len, GFP_KERNEL);
+	if (!drm_vtcon_vc->text_buf)
+		goto err_free;
+
+	mutex_init(&drm_vtcon_vc->lock);
+	vtcon_instance = vtcon;
+
+	return 0;
+
+err_free:
+	kfree(drm_vtcon_vc);
+	kfree(vtcon);
+
+	return -ENOMEM;
+}
+
+static int __init drm_vtcon_module_init(void)
+{
+	int ret;
+
+	if (drm_vtcon_dev_id < 0)
+		return 0;
+
+	ret = drm_vtcon_setup();
+	if (ret)
+		return ret;
+
+	vtcon_client = drm_vtcon_client_new(drm_vtcon_dev_id);
+	if (IS_ERR(vtcon_client)) {
+		ret = PTR_ERR(vtcon_client);
+		drm_vtcon_dev_id = ret;
+		goto err_free;
+	}
+
+	console_lock();
+	ret = do_take_over_console(&drm_vtcon_consw, 0, 1, 0);
+	console_unlock();
+	if (ret)
+		goto err_remove;
+
+	return 0;
+
+err_remove:
+	drm_client_remove(vtcon_client);
+err_free:
+	drm_vtcon_teardown();
+
+	return ret;
+}
+module_init(drm_vtcon_module_init);
+
+static void __exit drm_vtcon_module_exit(void)
+{
+	if (drm_vtcon_dev_id < 0)
+		return;
+
+	mutex_lock(&vtcon_client_lock);
+	drm_client_remove(vtcon_client);
+	mutex_unlock(&vtcon_client_lock);
+
+	console_lock();
+	do_unbind_con_driver(&drm_vtcon_consw, 0, 1, 0);
+	do_unregister_con_driver(&drm_vtcon_consw);
+	console_unlock();
+
+	del_timer_sync(&drm_vtcon_con_cursor_timer);
+	flush_work(&drm_vtcon_work);
+	drm_vtcon_teardown();
+}
+module_exit(drm_vtcon_module_exit);
+
+MODULE_LICENSE("GPL");
-- 
2.15.1

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