text: /*
   * Copyright (C) 2013 Noralf Tronnes
   *
   * This driver is inspired by:
   *   st7735fb.c, Copyright (C) 2011, Matt Porter
   *   broadsheetfb.c, Copyright (C) 2008, Jaya Kumar
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   */
  
  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/errno.h>
  #include <linux/string.h>
  #include <linux/mm.h>
  #include <linux/vmalloc.h>
  #include <linux/slab.h>
  #include <linux/init.h>
  #include <linux/fb.h>
  #include <linux/gpio.h>
  #include <linux/spi/spi.h>
  #include <linux/delay.h>
  #include <linux/uaccess.h>
  #include <linux/backlight.h>
  #include <linux/platform_device.h>
  #include <linux/spinlock.h>
  #include <linux/of.h>
  #include <linux/of_gpio.h>
  #include <video/mipi_display.h>
  
  #include "fbtft.h"
  #include "internal.h"
  
  static unsigned long debug;
  module_param(debug, ulong, 0000);
  MODULE_PARM_DESC(debug, "override device debug level");
  
  int fbtft_write_buf_dc(struct fbtft_par *par, void *buf, size_t len, int dc)
  {
  	int ret;
  
  	if (gpio_is_valid(par->gpio.dc))
  		gpio_set_value(par->gpio.dc, dc);
  
  	ret = par->fbtftops.write(par, buf, len);
  	if (ret < 0)
  		dev_err(par->info->device,
  			"write() failed and returned %d\n", ret);
  	return ret;
  }
  EXPORT_SYMBOL(fbtft_write_buf_dc);
  
  void fbtft_dbg_hex(const struct device *dev, int groupsize,
  		   void *buf, size_t len, const char *fmt, ...)
  {
  	va_list args;
  	static char textbuf[512];
  	char *text = textbuf;
  	size_t text_len;
  
  	va_start(args, fmt);
  	text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
  	va_end(args);
  
  	hex_dump_to_buffer(buf, len, 32, groupsize, text + text_len,
  			   512 - text_len, false);
  
  	if (len > 32)
  		dev_info(dev, "%s ...\n", text);
  	else
  		dev_info(dev, "%s\n", text);
  }
  EXPORT_SYMBOL(fbtft_dbg_hex);
  
  static unsigned long fbtft_request_gpios_match(struct fbtft_par *par,
  					       const struct fbtft_gpio *gpio)
  {
  	int ret;
  	long val;
  
  	fbtft_par_dbg(DEBUG_REQUEST_GPIOS_MATCH, par, "%s('%s')\n",
  		      __func__, gpio->name);
  
  	if (strcasecmp(gpio->name, "reset") == 0) {
  		par->gpio.reset = gpio->gpio;
  		return GPIOF_OUT_INIT_HIGH;
  	} else if (strcasecmp(gpio->name, "dc") == 0) {
  		par->gpio.dc = gpio->gpio;
  		return GPIOF_OUT_INIT_LOW;
  	} else if (strcasecmp(gpio->name, "cs") == 0) {
  		par->gpio.cs = gpio->gpio;
  		return GPIOF_OUT_INIT_HIGH;
  	} else if (strcasecmp(gpio->name, "wr") == 0) {
  		par->gpio.wr = gpio->gpio;
  		return GPIOF_OUT_INIT_HIGH;
  	} else if (strcasecmp(gpio->name, "rd") == 0) {
  		par->gpio.rd = gpio->gpio;
  		return GPIOF_OUT_INIT_HIGH;
  	} else if (strcasecmp(gpio->name, "latch") == 0) {
  		par->gpio.latch = gpio->gpio;
  		return GPIOF_OUT_INIT_LOW;
  	} else if (gpio->name[0] == 'd' && gpio->name[1] == 'b') {
  		ret = kstrtol(&gpio->name[2], 10, &val);
  		if (ret == 0 && val < 16) {
  			par->gpio.db[val] = gpio->gpio;
  			return GPIOF_OUT_INIT_LOW;
  		}
  	} else if (strcasecmp(gpio->name, "led") == 0) {
  		par->gpio.led[0] = gpio->gpio;
  		return GPIOF_OUT_INIT_LOW;
  	} else if (strcasecmp(gpio->name, "led_") == 0) {
  		par->gpio.led[0] = gpio->gpio;
  		return GPIOF_OUT_INIT_HIGH;
  	}
  
  	return FBTFT_GPIO_NO_MATCH;
  }
  
  static int fbtft_request_gpios(struct fbtft_par *par)
  {
  	struct fbtft_platform_data *pdata = par->pdata;
  	const struct fbtft_gpio *gpio;
  	unsigned long flags;
  	int ret;
  
  	if (!(pdata && pdata->gpios))
  		return 0;
  
  	gpio = pdata->gpios;
  	while (gpio->name[0]) {
  		flags = FBTFT_GPIO_NO_MATCH;
  		/* if driver provides match function, try it first,
  		 * if no match use our own
  		 */
  		if (par->fbtftops.request_gpios_match)
  			flags = par->fbtftops.request_gpios_match(par, gpio);
  		if (flags == FBTFT_GPIO_NO_MATCH)
  			flags = fbtft_request_gpios_match(par, gpio);
  		if (flags != FBTFT_GPIO_NO_MATCH) {
  			ret = devm_gpio_request_one(par->info->device,
  					gpio->gpio, flags,
  					par->info->device->driver->name);
  			if (ret < 0) {
  				dev_err(par->info->device,
  					"%s: gpio_request_one('%s'=%d) failed with %d\n",
  					__func__, gpio->name,
  					gpio->gpio, ret);
  				return ret;
  			}
  			fbtft_par_dbg(DEBUG_REQUEST_GPIOS, par,
  				      "%s: '%s' = GPIO%d\n",
  				      __func__, gpio->name, gpio->gpio);
  		}
  		gpio++;
  	}
  
  	return 0;
  }
  
  #ifdef CONFIG_OF
  static int fbtft_request_one_gpio(struct fbtft_par *par,
  				  const char *name, int index, int *gpiop)
  {
  	struct device *dev = par->info->device;
  	struct device_node *node = dev->of_node;
  	int gpio, flags, ret = 0;
  	enum of_gpio_flags of_flags;
  
  	if (of_find_property(node, name, NULL)) {
  		gpio = of_get_named_gpio_flags(node, name, index, &of_flags);
  		if (gpio == -ENOENT)
  			return 0;
  		if (gpio == -EPROBE_DEFER)
  			return gpio;
  		if (gpio < 0) {
  			dev_err(dev,
  				"failed to get '%s' from DT\n", name);
  			return gpio;
  		}
  
  		/* active low translates to initially low */
  		flags = (of_flags & OF_GPIO_ACTIVE_LOW) ? GPIOF_OUT_INIT_LOW :
  							GPIOF_OUT_INIT_HIGH;
  		ret = devm_gpio_request_one(dev, gpio, flags,
  					    dev->driver->name);
  		if (ret) {
  			dev_err(dev,
  				"gpio_request_one('%s'=%d) failed with %d\n",
  				name, gpio, ret);
  			return ret;
  		}
  		if (gpiop)
  			*gpiop = gpio;
  		fbtft_par_dbg(DEBUG_REQUEST_GPIOS, par, "%s: '%s' = GPIO%d\n",
  			      __func__, name, gpio);
  	}
  
  	return ret;
  }
  
  static int fbtft_request_gpios_dt(struct fbtft_par *par)
  {
  	int i;
  	int ret;
  
  	if (!par->info->device->of_node)
  		return -EINVAL;
  
  	ret = fbtft_request_one_gpio(par, "reset-gpios", 0, &par->gpio.reset);
  	if (ret)
  		return ret;
  	ret = fbtft_request_one_gpio(par, "dc-gpios", 0, &par->gpio.dc);
  	if (ret)
  		return ret;
  	ret = fbtft_request_one_gpio(par, "rd-gpios", 0, &par->gpio.rd);
  	if (ret)
  		return ret;
  	ret = fbtft_request_one_gpio(par, "wr-gpios", 0, &par->gpio.wr);
  	if (ret)
  		return ret;
  	ret = fbtft_request_one_gpio(par, "cs-gpios", 0, &par->gpio.cs);
  	if (ret)
  		return ret;
  	ret = fbtft_request_one_gpio(par, "latch-gpios", 0, &par->gpio.latch);
  	if (ret)
  		return ret;
  	for (i = 0; i < 16; i++) {
  		ret = fbtft_request_one_gpio(par, "db-gpios", i,
  					     &par->gpio.db[i]);
  		if (ret)
  			return ret;
  		ret = fbtft_request_one_gpio(par, "led-gpios", i,
  					     &par->gpio.led[i]);
  		if (ret)
  			return ret;
  		ret = fbtft_request_one_gpio(par, "aux-gpios", i,
  					     &par->gpio.aux[i]);
  		if (ret)
  			return ret;
  	}
  
  	return 0;
  }
  #endif
  
  #ifdef CONFIG_FB_BACKLIGHT
  static int fbtft_backlight_update_status(struct backlight_device *bd)
  {
  	struct fbtft_par *par = bl_get_data(bd);
  	bool polarity = !!(bd->props.state & BL_CORE_DRIVER1);
  
  	fbtft_par_dbg(DEBUG_BACKLIGHT, par,
  		"%s: polarity=%d, power=%d, fb_blank=%d\n",
  		__func__, polarity, bd->props.power, bd->props.fb_blank);
  
  	if ((bd->props.power == FB_BLANK_UNBLANK) &&
  	    (bd->props.fb_blank == FB_BLANK_UNBLANK))
  		gpio_set_value(par->gpio.led[0], polarity);
  	else
  		gpio_set_value(par->gpio.led[0], !polarity);
  
  	return 0;
  }
  
  static int fbtft_backlight_get_brightness(struct backlight_device *bd)
  {
  	return bd->props.brightness;
  }
  
  void fbtft_unregister_backlight(struct fbtft_par *par)
  {
  	if (par->info->bl_dev) {
  		par->info->bl_dev->props.power = FB_BLANK_POWERDOWN;
  		backlight_update_status(par->info->bl_dev);
  		backlight_device_unregister(par->info->bl_dev);
  		par->info->bl_dev = NULL;
  	}
  }
  
  static const struct backlight_ops fbtft_bl_ops = {
  	.get_brightness	= fbtft_backlight_get_brightness,
  	.update_status	= fbtft_backlight_update_status,
  };
  
  void fbtft_register_backlight(struct fbtft_par *par)
  {
  	struct backlight_device *bd;
  	struct backlight_properties bl_props = { 0, };
  
  	if (par->gpio.led[0] == -1) {
  		fbtft_par_dbg(DEBUG_BACKLIGHT, par,
  			      "%s(): led pin not set, exiting.\n", __func__);
  		return;
  	}
  
  	bl_props.type = BACKLIGHT_RAW;
  	/* Assume backlight is off, get polarity from current state of pin */
  	bl_props.power = FB_BLANK_POWERDOWN;
  	if (!gpio_get_value(par->gpio.led[0]))
  		bl_props.state |= BL_CORE_DRIVER1;
  
  	bd = backlight_device_register(dev_driver_string(par->info->device),
  				       par->info->device, par,
  				       &fbtft_bl_ops, &bl_props);
  	if (IS_ERR(bd)) {
  		dev_err(par->info->device,
  			"cannot register backlight device (%ld)\n",
  			PTR_ERR(bd));
  		return;
  	}
  	par->info->bl_dev = bd;
  
  	if (!par->fbtftops.unregister_backlight)
  		par->fbtftops.unregister_backlight = fbtft_unregister_backlight;
  }
  #else
  void fbtft_register_backlight(struct fbtft_par *par) { };
  void fbtft_unregister_backlight(struct fbtft_par *par) { };
  #endif
  EXPORT_SYMBOL(fbtft_register_backlight);
  EXPORT_SYMBOL(fbtft_unregister_backlight);
  
  static void fbtft_set_addr_win(struct fbtft_par *par, int xs, int ys, int xe,
  			       int ye)
  {
  	write_reg(par, MIPI_DCS_SET_COLUMN_ADDRESS,
  		  (xs >> 8) & 0xFF, xs & 0xFF, (xe >> 8) & 0xFF, xe & 0xFF);
  
  	write_reg(par, MIPI_DCS_SET_PAGE_ADDRESS,
  		  (ys >> 8) & 0xFF, ys & 0xFF, (ye >> 8) & 0xFF, ye & 0xFF);
  
  	write_reg(par, MIPI_DCS_WRITE_MEMORY_START);
  }
  
  static void fbtft_reset(struct fbtft_par *par)
  {
  	if (par->gpio.reset == -1)
  		return;
  	fbtft_par_dbg(DEBUG_RESET, par, "%s()\n", __func__);
  	gpio_set_value_cansleep(par->gpio.reset, 0);
  	usleep_range(20, 40);
  	gpio_set_value_cansleep(par->gpio.reset, 1);
  	msleep(120);
  }
  
  static void fbtft_update_display(struct fbtft_par *par, unsigned int start_line,
  				 unsigned int end_line)
  {
  	size_t offset, len;
  	ktime_t ts_start, ts_end;
  	long fps, throughput;
  	bool timeit = false;
  	int ret = 0;
  
  	if (unlikely(par->debug & (DEBUG_TIME_FIRST_UPDATE |
  			DEBUG_TIME_EACH_UPDATE))) {
  		if ((par->debug & DEBUG_TIME_EACH_UPDATE) ||
  		    ((par->debug & DEBUG_TIME_FIRST_UPDATE) &&
  		    !par->first_update_done)) {
  			ts_start = ktime_get();
  			timeit = true;
  		}
  	}
  
  	/* Sanity checks */
  	if (start_line > end_line) {
  		dev_warn(par->info->device,
  			 "%s: start_line=%u is larger than end_line=%u. Shouldn't happen, will do full display update\n",
  			 __func__, start_line, end_line);
  		start_line = 0;
  		end_line = par->info->var.yres - 1;
  	}
  	if (start_line > par->info->var.yres - 1 ||
  	    end_line > par->info->var.yres - 1) {
  		dev_warn(par->info->device,
  			"%s: start_line=%u or end_line=%u is larger than max=%d. Shouldn't happen, will do full display update\n",
  			 __func__, start_line,
  			 end_line, par->info->var.yres - 1);
  		start_line = 0;
  		end_line = par->info->var.yres - 1;
  	}
  
  	fbtft_par_dbg(DEBUG_UPDATE_DISPLAY, par, "%s(start_line=%u, end_line=%u)\n",
  		      __func__, start_line, end_line);
  
  	if (par->fbtftops.set_addr_win)
  		par->fbtftops.set_addr_win(par, 0, start_line,
  				par->info->var.xres - 1, end_line);
  
  	offset = start_line * par->info->fix.line_length;
  	len = (end_line - start_line + 1) * par->info->fix.line_length;
  	ret = par->fbtftops.write_vmem(par, offset, len);
  	if (ret < 0)
  		dev_err(par->info->device,
  			"%s: write_vmem failed to update display buffer\n",
  			__func__);
  
  	if (unlikely(timeit)) {
  		ts_end = ktime_get();
  		if (!ktime_to_ns(par->update_time))
  			par->update_time = ts_start;
  
  		fps = ktime_us_delta(ts_start, par->update_time);
  		par->update_time = ts_start;
  		fps = fps ? 1000000 / fps : 0;
  
  		throughput = ktime_us_delta(ts_end, ts_start);
  		throughput = throughput ? (len * 1000) / throughput : 0;
  		throughput = throughput * 1000 / 1024;
  
  		dev_info(par->info->device,
  			 "Display update: %ld kB/s, fps=%ld\n",
  			 throughput, fps);
  		par->first_update_done = true;
  	}
  }
  
  static void fbtft_mkdirty(struct fb_info *info, int y, int height)
  {
  	struct fbtft_par *par = info->par;
  	struct fb_deferred_io *fbdefio = info->fbdefio;
  
  	/* special case, needed ? */
  	if (y == -1) {
  		y = 0;
  		height = info->var.yres - 1;
  	}
  
  	/* Mark display lines/area as dirty */
  	spin_lock(&par->dirty_lock);
  	if (y < par->dirty_lines_start)
  		par->dirty_lines_start = y;
  	if (y + height - 1 > par->dirty_lines_end)
  		par->dirty_lines_end = y + height - 1;
  	spin_unlock(&par->dirty_lock);
  
  	/* Schedule deferred_io to update display (no-op if already on queue)*/
  	schedule_delayed_work(&info->deferred_work, fbdefio->delay);
  }
  
  static void fbtft_deferred_io(struct fb_info *info, struct list_head *pagelist)
  {
  	struct fbtft_par *par = info->par;
  	unsigned int dirty_lines_start, dirty_lines_end;
  	struct page *page;
  	unsigned long index;
  	unsigned int y_low = 0, y_high = 0;
  	int count = 0;
  
  	spin_lock(&par->dirty_lock);
  	dirty_lines_start = par->dirty_lines_start;
  	dirty_lines_end = par->dirty_lines_end;
  	/* set display line markers as clean */
  	par->dirty_lines_start = par->info->var.yres - 1;
  	par->dirty_lines_end = 0;
  	spin_unlock(&par->dirty_lock);
  
  	/* Mark display lines as dirty */
  	list_for_each_entry(page, pagelist, lru) {
  		count++;
  		index = page->index << PAGE_SHIFT;
  		y_low = index / info->fix.line_length;
  		y_high = (index + PAGE_SIZE - 1) / info->fix.line_length;
  		dev_dbg(info->device,
  			"page->index=%lu y_low=%d y_high=%d\n",
  			page->index, y_low, y_high);
  		if (y_high > info->var.yres - 1)
  			y_high = info->var.yres - 1;
  		if (y_low < dirty_lines_start)
  			dirty_lines_start = y_low;
  		if (y_high > dirty_lines_end)
  			dirty_lines_end = y_high;
  	}
  
  	par->fbtftops.update_display(info->par,
  					dirty_lines_start, dirty_lines_end);
  }
  
  static void fbtft_fb_fillrect(struct fb_info *info,
  			      const struct fb_fillrect *rect)
  {
  	struct fbtft_par *par = info->par;
  
  	dev_dbg(info->dev,
  		"%s: dx=%d, dy=%d, width=%d, height=%d\n",
  		__func__, rect->dx, rect->dy, rect->width, rect->height);
  	sys_fillrect(info, rect);
  
  	par->fbtftops.mkdirty(info, rect->dy, rect->height);
  }
  
  static void fbtft_fb_copyarea(struct fb_info *info,
  			      const struct fb_copyarea *area)
  {
  	struct fbtft_par *par = info->par;
  
  	dev_dbg(info->dev,
  		"%s: dx=%d, dy=%d, width=%d, height=%d\n",
  		__func__,  area->dx, area->dy, area->width, area->height);
  	sys_copyarea(info, area);
  
  	par->fbtftops.mkdirty(info, area->dy, area->height);
  }
  
  static void fbtft_fb_imageblit(struct fb_info *info,
  			       const struct fb_image *image)
  {
  	struct fbtft_par *par = info->par;
  
  	dev_dbg(info->dev,
  		"%s: dx=%d, dy=%d, width=%d, height=%d\n",
  		__func__,  image->dx, image->dy, image->width, image->height);
  	sys_imageblit(info, image);
  
  	par->fbtftops.mkdirty(info, image->dy, image->height);
  }
  
  static ssize_t fbtft_fb_write(struct fb_info *info, const char __user *buf,
  			      size_t count, loff_t *ppos)
  {
  	struct fbtft_par *par = info->par;
  	ssize_t res;
  
  	dev_dbg(info->dev,
  		"%s: count=%zd, ppos=%llu\n", __func__,  count, *ppos);
  	res = fb_sys_write(info, buf, count, ppos);
  
  	/* TODO: only mark changed area update all for now */
  	par->fbtftops.mkdirty(info, -1, 0);
  
  	return res;
  }
  
  /* from pxafb.c */
  static unsigned int chan_to_field(unsigned int chan, struct fb_bitfield *bf)
  {
  	chan &= 0xffff;
  	chan >>= 16 - bf->length;
  	return chan << bf->offset;
  }
  
  static int fbtft_fb_setcolreg(unsigned int regno, unsigned int red, unsigned int green,
  			      unsigned int blue, unsigned int transp,
  			      struct fb_info *info)
  {
  	unsigned int val;
  	int ret = 1;
  
  	dev_dbg(info->dev,
  		"%s(regno=%u, red=0x%X, green=0x%X, blue=0x%X, trans=0x%X)\n",
  		__func__, regno, red, green, blue, transp);
  
  	switch (info->fix.visual) {
  	case FB_VISUAL_TRUECOLOR:
  		if (regno < 16) {
  			u32 *pal = info->pseudo_palette;
  
  			val  = chan_to_field(red,   &info->var.red);
  			val |= chan_to_field(green, &info->var.green);
  			val |= chan_to_field(blue,  &info->var.blue);
  
  			pal[regno] = val;
  			ret = 0;
  		}
  		break;
  	}
  	return ret;
  }
  
  static int fbtft_fb_blank(int blank, struct fb_info *info)
  {
  	struct fbtft_par *par = info->par;
  	int ret = -EINVAL;
  
  	dev_dbg(info->dev, "%s(blank=%d)\n",
  		__func__, blank);
  
  	if (!par->fbtftops.blank)
  		return ret;
  
  	switch (blank) {
  	case FB_BLANK_POWERDOWN:
  	case FB_BLANK_VSYNC_SUSPEND:
  	case FB_BLANK_HSYNC_SUSPEND:
  	case FB_BLANK_NORMAL:
  		ret = par->fbtftops.blank(par, true);
  		break;
  	case FB_BLANK_UNBLANK:
  		ret = par->fbtftops.blank(par, false);
  		break;
  	}
  	return ret;
  }
  
  static void fbtft_merge_fbtftops(struct fbtft_ops *dst, struct fbtft_ops *src)
  {
  	if (src->write)
  		dst->write = src->write;
  	if (src->read)
  		dst->read = src->read;
  	if (src->write_vmem)
  		dst->write_vmem = src->write_vmem;
  	if (src->write_register)
  		dst->write_register = src->write_register;
  	if (src->set_addr_win)
  		dst->set_addr_win = src->set_addr_win;
  	if (src->reset)
  		dst->reset = src->reset;
  	if (src->mkdirty)
  		dst->mkdirty = src->mkdirty;
  	if (src->update_display)
  		dst->update_display = src->update_display;
  	if (src->init_display)
  		dst->init_display = src->init_display;
  	if (src->blank)
  		dst->blank = src->blank;
  	if (src->request_gpios_match)
  		dst->request_gpios_match = src->request_gpios_match;
  	if (src->request_gpios)
  		dst->request_gpios = src->request_gpios;
  	if (src->verify_gpios)
  		dst->verify_gpios = src->verify_gpios;
  	if (src->register_backlight)
  		dst->register_backlight = src->register_backlight;
  	if (src->unregister_backlight)
  		dst->unregister_backlight = src->unregister_backlight;
  	if (src->set_var)
  		dst->set_var = src->set_var;
  	if (src->set_gamma)
  		dst->set_gamma = src->set_gamma;
  }
  
  /**
   * fbtft_framebuffer_alloc - creates a new frame buffer info structure
   *
   * @display: pointer to structure describing the display
   * @dev: pointer to the device for this fb, this can be NULL
   *
   * Creates a new frame buffer info structure.
   *
   * Also creates and populates the following structures:
   *   info->fbops
   *   info->fbdefio
   *   info->pseudo_palette
   *   par->fbtftops
   *   par->txbuf
   *
   * Returns the new structure, or NULL if an error occurred.
   *
   */
  struct fb_info *fbtft_framebuffer_alloc(struct fbtft_display *display,
  					struct device *dev,
  					struct fbtft_platform_data *pdata)
  {
  	struct fb_info *info;
  	struct fbtft_par *par;
  	struct fb_ops *fbops = NULL;
  	struct fb_deferred_io *fbdefio = NULL;
  	u8 *vmem = NULL;
  	void *txbuf = NULL;
  	void *buf = NULL;
  	unsigned int width;
  	unsigned int height;
  	int txbuflen = display->txbuflen;
  	unsigned int bpp = display->bpp;
  	unsigned int fps = display->fps;
  	int vmem_size, i;
  	const s16 *init_sequence = display->init_sequence;
  	char *gamma = display->gamma;
  	u32 *gamma_curves = NULL;
  
  	/* sanity check */
  	if (display->gamma_num * display->gamma_len >
  			FBTFT_GAMMA_MAX_VALUES_TOTAL) {
  		dev_err(dev, "FBTFT_GAMMA_MAX_VALUES_TOTAL=%d is exceeded\n",
  			FBTFT_GAMMA_MAX_VALUES_TOTAL);
  		return NULL;
  	}
  
  	/* defaults */
  	if (!fps)
  		fps = 20;
  	if (!bpp)
  		bpp = 16;
  
  	if (!pdata) {
  		dev_err(dev, "platform data is missing\n");
  		return NULL;
  	}
  
  	/* override driver values? */
  	if (pdata->fps)
  		fps = pdata->fps;
  	if (pdata->txbuflen)
  		txbuflen = pdata->txbuflen;
  	if (pdata->display.init_sequence)
  		init_sequence = pdata->display.init_sequence;
  	if (pdata->gamma)
  		gamma = pdata->gamma;
  	if (pdata->display.debug)
  		display->debug = pdata->display.debug;
  	if (pdata->display.backlight)
  		display->backlight = pdata->display.backlight;
  	if (pdata->display.width)
  		display->width = pdata->display.width;
  	if (pdata->display.height)
  		display->height = pdata->display.height;
  	if (pdata->display.buswidth)
  		display->buswidth = pdata->display.buswidth;
  	if (pdata->display.regwidth)
  		display->regwidth = pdata->display.regwidth;
  
  	display->debug |= debug;
  	fbtft_expand_debug_value(&display->debug);
  
  	switch (pdata->rotate) {
  	case 90:
  	case 270:
  		width =  display->height;
  		height = display->width;
  		break;
  	default:
  		width =  display->width;
  		height = display->height;
  	}
  
  	vmem_size = display->width * display->height * bpp / 8;
  	vmem = vzalloc(vmem_size);
  	if (!vmem)
  		goto alloc_fail;
  
  	fbops = devm_kzalloc(dev, sizeof(struct fb_ops), GFP_KERNEL);
  	if (!fbops)
  		goto alloc_fail;
  
  	fbdefio = devm_kzalloc(dev, sizeof(struct fb_deferred_io), GFP_KERNEL);
  	if (!fbdefio)
  		goto alloc_fail;
  
  	buf = devm_kzalloc(dev, 128, GFP_KERNEL);
  	if (!buf)
  		goto alloc_fail;
  
  	if (display->gamma_num && display->gamma_len) {
  		gamma_curves = devm_kcalloc(dev,
  					    display->gamma_num *
  					    display->gamma_len,
  					    sizeof(gamma_curves[0]),
  					    GFP_KERNEL);
  		if (!gamma_curves)
  			goto alloc_fail;
  	}
  
  	info = framebuffer_alloc(sizeof(struct fbtft_par), dev);
  	if (!info)
  		goto alloc_fail;
  
  	info->screen_buffer = vmem;
  	info->fbops = fbops;
  	info->fbdefio = fbdefio;
  
  	fbops->owner        =      dev->driver->owner;
  	fbops->fb_read      =      fb_sys_read;
  	fbops->fb_write     =      fbtft_fb_write;
  	fbops->fb_fillrect  =      fbtft_fb_fillrect;
  	fbops->fb_copyarea  =      fbtft_fb_copyarea;
  	fbops->fb_imageblit =      fbtft_fb_imageblit;
  	fbops->fb_setcolreg =      fbtft_fb_setcolreg;
  	fbops->fb_blank     =      fbtft_fb_blank;
  
  	fbdefio->delay =           HZ/fps;
  	fbdefio->deferred_io =     fbtft_deferred_io;
  	fb_deferred_io_init(info);
  
  	strncpy(info->fix.id, dev->driver->name, 16);
  	info->fix.type =           FB_TYPE_PACKED_PIXELS;
  	info->fix.visual =         FB_VISUAL_TRUECOLOR;
  	info->fix.xpanstep =	   0;
  	info->fix.ypanstep =	   0;
  	info->fix.ywrapstep =	   0;
  	info->fix.line_length =    width * bpp / 8;
  	info->fix.accel =          FB_ACCEL_NONE;
  	info->fix.smem_len =       vmem_size;
  
  	info->var.rotate =         pdata->rotate;
  	info->var.xres =           width;
  	info->var.yres =           height;
  	info->var.xres_virtual =   info->var.xres;
  	info->var.yres_virtual =   info->var.yres;
  	info->var.bits_per_pixel = bpp;
  	info->var.nonstd =         1;
  
  	/* RGB565 */
  	info->var.red.offset =     11;
  	info->var.red.length =     5;
  	info->var.green.offset =   5;
  	info->var.green.length =   6;
  	info->var.blue.offset =    0;
  	info->var.blue.length =    5;
  	info->var.transp.offset =  0;
  	info->var.transp.length =  0;
  
  	info->flags =              FBINFO_FLAG_DEFAULT | FBINFO_VIRTFB;
  
  	par = info->par;
  	par->info = info;
  	par->pdata = pdata;
  	par->debug = display->debug;
  	par->buf = buf;
  	spin_lock_init(&par->dirty_lock);
  	par->bgr = pdata->bgr;
  	par->startbyte = pdata->startbyte;
  	par->init_sequence = init_sequence;
  	par->gamma.curves = gamma_curves;
  	par->gamma.num_curves = display->gamma_num;
  	par->gamma.num_values = display->gamma_len;
  	mutex_init(&par->gamma.lock);
  	info->pseudo_palette = par->pseudo_palette;
  
  	if (par->gamma.curves && gamma) {
  		if (fbtft_gamma_parse_str(par,
  			par->gamma.curves, gamma, strlen(gamma)))
  			goto alloc_fail;
  	}
  
  	/* Transmit buffer */
  	if (txbuflen == -1)
  		txbuflen = vmem_size + 2; /* add in case startbyte is used */
  	if (txbuflen >= vmem_size + 2)
  		txbuflen = 0;
  
  #ifdef __LITTLE_ENDIAN
  	if ((!txbuflen) && (bpp > 8))
  		txbuflen = PAGE_SIZE; /* need buffer for byteswapping */
  #endif
  
  	if (txbuflen > 0) {
  		txbuf = devm_kzalloc(par->info->device, txbuflen, GFP_KERNEL);
  		if (!txbuf)
  			goto alloc_fail;
  		par->txbuf.buf = txbuf;
  		par->txbuf.len = txbuflen;
  	}
  
  	/* Initialize gpios to disabled */
  	par->gpio.reset = -1;
  	par->gpio.dc = -1;
  	par->gpio.rd = -1;
  	par->gpio.wr = -1;
  	par->gpio.cs = -1;
  	par->gpio.latch = -1;
  	for (i = 0; i < 16; i++) {
  		par->gpio.db[i] = -1;
  		par->gpio.led[i] = -1;
  		par->gpio.aux[i] = -1;
  	}
  
  	/* default fbtft operations */
  	par->fbtftops.write = fbtft_write_spi;
  	par->fbtftops.read = fbtft_read_spi;
  	par->fbtftops.write_vmem = fbtft_write_vmem16_bus8;
  	par->fbtftops.write_register = fbtft_write_reg8_bus8;
  	par->fbtftops.set_addr_win = fbtft_set_addr_win;
  	par->fbtftops.reset = fbtft_reset;
  	par->fbtftops.mkdirty = fbtft_mkdirty;
  	par->fbtftops.update_display = fbtft_update_display;
  	par->fbtftops.request_gpios = fbtft_request_gpios;
  	if (display->backlight)
  		par->fbtftops.register_backlight = fbtft_register_backlight;
  
  	/* use driver provided functions */
  	fbtft_merge_fbtftops(&par->fbtftops, &display->fbtftops);
  
  	return info;
  
  alloc_fail:
  	vfree(vmem);
  
  	return NULL;
  }
  EXPORT_SYMBOL(fbtft_framebuffer_alloc);
  
  /**
   * fbtft_framebuffer_release - frees up all memory used by the framebuffer
   *
   * @info: frame buffer info structure
   *
   */
  void fbtft_framebuffer_release(struct fb_info *info)
  {
  	fb_deferred_io_cleanup(info);
  	vfree(info->screen_buffer);
  	framebuffer_release(info);
  }
  EXPORT_SYMBOL(fbtft_framebuffer_release);
  
  /**
   *	fbtft_register_framebuffer - registers a tft frame buffer device
   *	@fb_info: frame buffer info structure
   *
   *  Sets SPI driverdata if needed
   *  Requests needed gpios.
   *  Initializes display
   *  Updates display.
   *	Registers a frame buffer device @fb_info.
   *
   *	Returns negative errno on error, or zero for success.
   *
   */
  int fbtft_register_framebuffer(struct fb_info *fb_info)
  {
  	int ret;
  	char text1[50] = "";
  	char text2[50] = "";
  	struct fbtft_par *par = fb_info->par;
  	struct spi_device *spi = par->spi;
  
  	/* sanity checks */
  	if (!par->fbtftops.init_display) {
  		dev_err(fb_info->device, "missing fbtftops.init_display()\n");
  		return -EINVAL;
  	}
  
  	if (spi)
  		spi_set_drvdata(spi, fb_info);
  	if (par->pdev)
  		platform_set_drvdata(par->pdev, fb_info);
  
  	ret = par->fbtftops.request_gpios(par);
  	if (ret < 0)
  		goto reg_fail;
  
  	if (par->fbtftops.verify_gpios) {
  		ret = par->fbtftops.verify_gpios(par);
  		if (ret < 0)
  			goto reg_fail;
  	}
  
  	ret = par->fbtftops.init_display(par);
  	if (ret < 0)
  		goto reg_fail;
  	if (par->fbtftops.set_var) {
  		ret = par->fbtftops.set_var(par);
  		if (ret < 0)
  			goto reg_fail;
  	}
  
  	/* update the entire display */
  	par->fbtftops.update_display(par, 0, par->info->var.yres - 1);
  
  	if (par->fbtftops.set_gamma && par->gamma.curves) {
  		ret = par->fbtftops.set_gamma(par, par->gamma.curves);
  		if (ret)
  			goto reg_fail;
  	}
  
  	if (par->fbtftops.register_backlight)
  		par->fbtftops.register_backlight(par);
  
  	ret = register_framebuffer(fb_info);
  	if (ret < 0)
  		goto reg_fail;
  
  	fbtft_sysfs_init(par);
  
  	if (par->txbuf.buf && par->txbuf.len >= 1024)
  		sprintf(text1, ", %zu KiB buffer memory", par->txbuf.len >> 10);
  	if (spi)
  		sprintf(text2, ", spi%d.%d at %d MHz", spi->master->bus_num,
  			spi->chip_select, spi->max_speed_hz / 1000000);
  	dev_info(fb_info->dev,
  		 "%s frame buffer, %dx%d, %d KiB video memory%s, fps=%lu%s\n",
  		 fb_info->fix.id, fb_info->var.xres, fb_info->var.yres,
  		 fb_info->fix.smem_len >> 10, text1,
  		 HZ / fb_info->fbdefio->delay, text2);
  
  #ifdef CONFIG_FB_BACKLIGHT
  	/* Turn on backlight if available */
  	if (fb_info->bl_dev) {
  		fb_info->bl_dev->props.power = FB_BLANK_UNBLANK;
  		fb_info->bl_dev->ops->update_status(fb_info->bl_dev);
  	}
  #endif
  
  	return 0;
  
  reg_fail:
  	if (par->fbtftops.unregister_backlight)
  		par->fbtftops.unregister_backlight(par);
  
  	return ret;
  }
  EXPORT_SYMBOL(fbtft_register_framebuffer);
  
  /**
   *	fbtft_unregister_framebuffer - releases a tft frame buffer device
   *	@fb_info: frame buffer info structure
   *
   *  Frees SPI driverdata if needed
   *  Frees gpios.
   *	Unregisters frame buffer device.
   *
   */
  int fbtft_unregister_framebuffer(struct fb_info *fb_info)
  {
  	struct fbtft_par *par = fb_info->par;
  
  	if (par->fbtftops.unregister_backlight)
  		par->fbtftops.unregister_backlight(par);
  	fbtft_sysfs_exit(par);
  	return unregister_framebuffer(fb_info);
  }
  EXPORT_SYMBOL(fbtft_unregister_framebuffer);
  
  #ifdef CONFIG_OF
  /**
   * fbtft_init_display_dt() - Device Tree init_display() function
   * @par: Driver data
   *
   * Return: 0 if successful, negative if error
   */
  static int fbtft_init_display_dt(struct fbtft_par *par)
  {
  	struct device_node *node = par->info->device->of_node;
  	struct property *prop;
  	const __be32 *p;
  	u32 val;
  	int buf[64], i, j;
  
  	if (!node)
  		return -EINVAL;
  
  	prop = of_find_property(node, "init", NULL);
  	p = of_prop_next_u32(prop, NULL, &val);
  	if (!p)
  		return -EINVAL;
  
  	par->fbtftops.reset(par);
  	if (par->gpio.cs != -1)
  		gpio_set_value(par->gpio.cs, 0);  /* Activate chip */
  
  	while (p) {
  		if (val & FBTFT_OF_INIT_CMD) {
  			val &= 0xFFFF;
  			i = 0;
  			while (p && !(val & 0xFFFF0000)) {
  				if (i > 63) {
  					dev_err(par->info->device,
  					"%s: Maximum register values exceeded\n",
  					__func__);
  					return -EINVAL;
  				}
  				buf[i++] = val;
  				p = of_prop_next_u32(prop, p, &val);
  			}
  			/* make debug message */
  			fbtft_par_dbg(DEBUG_INIT_DISPLAY, par,
  				      "init: write_register:\n");
  			for (j = 0; j < i; j++)
  				fbtft_par_dbg(DEBUG_INIT_DISPLAY, par,
  					      "buf[%d] = %02X\n", j, buf[j]);
  
  			par->fbtftops.write_register(par, i,
  				buf[0], buf[1], buf[2], buf[3],
  				buf[4], buf[5], buf[6], buf[7],
  				buf[8], buf[9], buf[10], buf[11],
  				buf[12], buf[13], buf[14], buf[15],
  				buf[16], buf[17], buf[18], buf[19],
  				buf[20], buf[21], buf[22], buf[23],
  				buf[24], buf[25], buf[26], buf[27],
  				buf[28], buf[29], buf[30], buf[31],
  				buf[32], buf[33], buf[34], buf[35],
  				buf[36], buf[37], buf[38], buf[39],
  				buf[40], buf[41], buf[42], buf[43],
  				buf[44], buf[45], buf[46], buf[47],
  				buf[48], buf[49], buf[50], buf[51],
  				buf[52], buf[53], buf[54], buf[55],
  				buf[56], buf[57], buf[58], buf[59],
  				buf[60], buf[61], buf[62], buf[63]);
  		} else if (val & FBTFT_OF_INIT_DELAY) {
  			fbtft_par_dbg(DEBUG_INIT_DISPLAY, par,
  				      "init: msleep(%u)\n", val & 0xFFFF);
  			msleep(val & 0xFFFF);
  			p = of_prop_next_u32(prop, p, &val);
  		} else {
  			dev_err(par->info->device, "illegal init value 0x%X\n",
  				val);
  			return -EINVAL;
  		}
  	}
  
  	return 0;
  }
  #endif
  
  /**
   * fbtft_init_display() - Generic init_display() function
   * @par: Driver data
   *
   * Uses par->init_sequence to do the initialization
   *
   * Return: 0 if successful, negative if error
   */
  int fbtft_init_display(struct fbtft_par *par)
  {
  	int buf[64];
  	char msg[128];
  	char str[16];
  	int i = 0;
  	int j;
  
  	/* sanity check */
  	if (!par->init_sequence) {
  		dev_err(par->info->device,
  			"error: init_sequence is not set\n");
  		return -EINVAL;
  	}
  
  	/* make sure stop marker exists */
  	for (i = 0; i < FBTFT_MAX_INIT_SEQUENCE; i++)
  		if (par->init_sequence[i] == -3)
  			break;
  	if (i == FBTFT_MAX_INIT_SEQUENCE) {
  		dev_err(par->info->device,
  			"missing stop marker at end of init sequence\n");
  		return -EINVAL;
  	}
  
  	par->fbtftops.reset(par);
  	if (par->gpio.cs != -1)
  		gpio_set_value(par->gpio.cs, 0);  /* Activate chip */
  
  	i = 0;
  	while (i < FBTFT_MAX_INIT_SEQUENCE) {
  		if (par->init_sequence[i] == -3) {
  			/* done */
  			return 0;
  		}
  		if (par->init_sequence[i] >= 0) {
  			dev_err(par->info->device,
  				"missing delimiter at position %d\n", i);
  			return -EINVAL;
  		}
  		if (par->init_sequence[i + 1] < 0) {
  			dev_err(par->info->device,
  				"missing value after delimiter %d at position %d\n",
  				par->init_sequence[i], i);
  			return -EINVAL;
  		}
  		switch (par->init_sequence[i]) {
  		case -1:
  			i++;
  			/* make debug message */
  			strcpy(msg, "");
  			j = i + 1;
  			while (par->init_sequence[j] >= 0) {
  				sprintf(str, "0x%02X ", par->init_sequence[j]);
  				strcat(msg, str);
  				j++;
  			}
  			fbtft_par_dbg(DEBUG_INIT_DISPLAY, par,
  				      "init: write(0x%02X) %s\n",
  				      par->init_sequence[i], msg);
  
  			/* Write */
  			j = 0;
  			while (par->init_sequence[i] >= 0) {
  				if (j > 63) {
  					dev_err(par->info->device,
  					"%s: Maximum register values exceeded\n",
  					__func__);
  					return -EINVAL;
  				}
  				buf[j++] = par->init_sequence[i++];
  			}
  			par->fbtftops.write_register(par, j,
  				buf[0], buf[1], buf[2], buf[3],
  				buf[4], buf[5], buf[6], buf[7],
  				buf[8], buf[9], buf[10], buf[11],
  				buf[12], buf[13], buf[14], buf[15],
  				buf[16], buf[17], buf[18], buf[19],
  				buf[20], buf[21], buf[22], buf[23],
  				buf[24], buf[25], buf[26], buf[27],
  				buf[28], buf[29], buf[30], buf[31],
  				buf[32], buf[33], buf[34], buf[35],
  				buf[36], buf[37], buf[38], buf[39],
  				buf[40], buf[41], buf[42], buf[43],
  				buf[44], buf[45], buf[46], buf[47],
  				buf[48], buf[49], buf[50], buf[51],
  				buf[52], buf[53], buf[54], buf[55],
  				buf[56], buf[57], buf[58], buf[59],
  				buf[60], buf[61], buf[62], buf[63]);
  			break;
  		case -2:
  			i++;
  			fbtft_par_dbg(DEBUG_INIT_DISPLAY, par,
  				"init: mdelay(%d)\n", par->init_sequence[i]);
  			mdelay(par->init_sequence[i++]);
  			break;
  		default:
  			dev_err(par->info->device,
  				"unknown delimiter %d at position %d\n",
  				par->init_sequence[i], i);
  			return -EINVAL;
  		}
  	}
  
  	dev_err(par->info->device,
  		"%s: something is wrong. Shouldn't get here.\n", __func__);
  	return -EINVAL;
  }
  EXPORT_SYMBOL(fbtft_init_display);
  
  /**
   * fbtft_verify_gpios() - Generic verify_gpios() function
   * @par: Driver data
   *
   * Uses @spi, @pdev and @buswidth to determine which GPIOs is needed
   *
   * Return: 0 if successful, negative if error
   */
  static int fbtft_verify_gpios(struct fbtft_par *par)
  {
  	struct fbtft_platform_data *pdata = par->pdata;
  	int i;
  
  	fbtft_par_dbg(DEBUG_VERIFY_GPIOS, par, "%s()\n", __func__);
  
  	if (pdata->display.buswidth != 9 && par->startbyte == 0 &&
  							par->gpio.dc < 0) {
  		dev_err(par->info->device,
  			"Missing info about 'dc' gpio. Aborting.\n");
  		return -EINVAL;
  	}
  
  	if (!par->pdev)
  		return 0;
  
  	if (par->gpio.wr < 0) {
  		dev_err(par->info->device, "Missing 'wr' gpio. Aborting.\n");
  		return -EINVAL;
  	}
  	for (i = 0; i < pdata->display.buswidth; i++) {
  		if (par->gpio.db[i] < 0) {
  			dev_err(par->info->device,
  				"Missing 'db%02d' gpio. Aborting.\n", i);
  			return -EINVAL;
  		}
  	}
  
  	return 0;
  }
  
  #ifdef CONFIG_OF
  /* returns 0 if the property is not present */
  static u32 fbtft_of_value(struct device_node *node, const char *propname)
  {
  	int ret;
  	u32 val = 0;
  
  	ret = of_property_read_u32(node, propname, &val);
  	if (ret == 0)
  		pr_info("%s: %s = %u\n", __func__, propname, val);
  
  	return val;
  }
  
  static struct fbtft_platform_data *fbtft_probe_dt(struct device *dev)
  {
  	struct device_node *node = dev->of_node;
  	struct fbtft_platform_data *pdata;
  
  	if (!node) {
  		dev_err(dev, "Missing platform data or DT\n");
  		return ERR_PTR(-EINVAL);
  	}
  
  	pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
  	if (!pdata)
  		return ERR_PTR(-ENOMEM);
  
  	pdata->display.width = fbtft_of_value(node, "width");
  	pdata->display.height = fbtft_of_value(node, "height");
  	pdata->display.regwidth = fbtft_of_value(node, "regwidth");
  	pdata->display.buswidth = fbtft_of_value(node, "buswidth");
  	pdata->display.backlight = fbtft_of_value(node, "backlight");
  	pdata->display.bpp = fbtft_of_value(node, "bpp");
  	pdata->display.debug = fbtft_of_value(node, "debug");
  	pdata->rotate = fbtft_of_value(node, "rotate");
  	pdata->bgr = of_property_read_bool(node, "bgr");
  	pdata->fps = fbtft_of_value(node, "fps");
  	pdata->txbuflen = fbtft_of_value(node, "txbuflen");
  	pdata->startbyte = fbtft_of_value(node, "startbyte");
  	of_property_read_string(node, "gamma", (const char **)&pdata->gamma);
  
  	if (of_find_property(node, "led-gpios", NULL))
  		pdata->display.backlight = 1;
  	if (of_find_property(node, "init", NULL))
  		pdata->display.fbtftops.init_display = fbtft_init_display_dt;
  	pdata->display.fbtftops.request_gpios = fbtft_request_gpios_dt;
  
  	return pdata;
  }
  #else
  static struct fbtft_platform_data *fbtft_probe_dt(struct device *dev)
  {
  	dev_err(dev, "Missing platform data\n");
  	return ERR_PTR(-EINVAL);
  }
  #endif
  
  /**
   * fbtft_probe_common() - Generic device probe() helper function
   * @display: Display properties
   * @sdev: SPI device
   * @pdev: Platform device
   *
   * Allocates, initializes and registers a framebuffer
   *
   * Either @sdev or @pdev should be NULL
   *
   * Return: 0 if successful, negative if error
   */
  int fbtft_probe_common(struct fbtft_display *display,
  			struct spi_device *sdev, struct platform_device *pdev)
  {
  	struct device *dev;
  	struct fb_info *info;
  	struct fbtft_par *par;
  	struct fbtft_platform_data *pdata;
  	int ret;
  
  	if (sdev)
  		dev = &sdev->dev;
  	else
  		dev = &pdev->dev;
  
  	if (unlikely(display->debug & DEBUG_DRIVER_INIT_FUNCTIONS))
  		dev_info(dev, "%s()\n", __func__);
  
  	pdata = dev->platform_data;
  	if (!pdata) {
  		pdata = fbtft_probe_dt(dev);
  		if (IS_ERR(pdata))
  			return PTR_ERR(pdata);
  	}
  
  	info = fbtft_framebuffer_alloc(display, dev, pdata);
  	if (!info)
  		return -ENOMEM;
  
  	par = info->par;
  	par->spi = sdev;
  	par->pdev = pdev;
  
  	if (display->buswidth == 0) {
  		dev_err(dev, "buswidth is not set\n");
  		return -EINVAL;
  	}
  
  	/* write register functions */
  	if (display->regwidth == 8 && display->buswidth == 8) {
  		par->fbtftops.write_register = fbtft_write_reg8_bus8;
  	} else
  	if (display->regwidth == 8 && display->buswidth == 9 && par->spi) {
  		par->fbtftops.write_register = fbtft_write_reg8_bus9;
  	} else if (display->regwidth == 16 && display->buswidth == 8) {
  		par->fbtftops.write_register = fbtft_write_reg16_bus8;
  	} else if (display->regwidth == 16 && display->buswidth == 16) {
  		par->fbtftops.write_register = fbtft_write_reg16_bus16;
  	} else {
  		dev_warn(dev,
  			"no default functions for regwidth=%d and buswidth=%d\n",
  			display->regwidth, display->buswidth);
  	}
  
  	/* write_vmem() functions */
  	if (display->buswidth == 8)
  		par->fbtftops.write_vmem = fbtft_write_vmem16_bus8;
  	else if (display->buswidth == 9)
  		par->fbtftops.write_vmem = fbtft_write_vmem16_bus9;
  	else if (display->buswidth == 16)
  		par->fbtftops.write_vmem = fbtft_write_vmem16_bus16;
  
  	/* GPIO write() functions */
  	if (par->pdev) {
  		if (display->buswidth == 8)
  			par->fbtftops.write = fbtft_write_gpio8_wr;
  		else if (display->buswidth == 16)
  			par->fbtftops.write = fbtft_write_gpio16_wr;
  	}
  
  	/* 9-bit SPI setup */
  	if (par->spi && display->buswidth == 9) {
  		if (par->spi->master->bits_per_word_mask & SPI_BPW_MASK(9)) {
  			par->spi->bits_per_word = 9;
  		} else {
  			dev_warn(&par->spi->dev,
  				"9-bit SPI not available, emulating using 8-bit.\n");
  			/* allocate buffer with room for dc bits */
  			par->extra = devm_kzalloc(par->info->device,
  				par->txbuf.len + (par->txbuf.len / 8) + 8,
  				GFP_KERNEL);
  			if (!par->extra) {
  				ret = -ENOMEM;
  				goto out_release;
  			}
  			par->fbtftops.write = fbtft_write_spi_emulate_9;
  		}
  	}
  
  	if (!par->fbtftops.verify_gpios)
  		par->fbtftops.verify_gpios = fbtft_verify_gpios;
  
  	/* make sure we still use the driver provided functions */
  	fbtft_merge_fbtftops(&par->fbtftops, &display->fbtftops);
  
  	/* use init_sequence if provided */
  	if (par->init_sequence)
  		par->fbtftops.init_display = fbtft_init_display;
  
  	/* use platform_data provided functions above all */
  	fbtft_merge_fbtftops(&par->fbtftops, &pdata->display.fbtftops);
  
  	ret = fbtft_register_framebuffer(info);
  	if (ret < 0)
  		goto out_release;
  
  	return 0;
  
  out_release:
  	fbtft_framebuffer_release(info);
  
  	return ret;
  }
  EXPORT_SYMBOL(fbtft_probe_common);
  
  /**
   * fbtft_remove_common() - Generic device remove() helper function
   * @dev: Device
   * @info: Framebuffer
   *
   * Unregisters and releases the framebuffer
   *
   * Return: 0 if successful, negative if error
   */
  int fbtft_remove_common(struct device *dev, struct fb_info *info)
  {
  	struct fbtft_par *par;
  
  	if (!info)
  		return -EINVAL;
  	par = info->par;
  	if (par)
  		fbtft_par_dbg(DEBUG_DRIVER_INIT_FUNCTIONS, par,
  			      "%s()\n", __func__);
  	fbtft_unregister_framebuffer(info);
  	fbtft_framebuffer_release(info);
  
  	return 0;
  }
  EXPORT_SYMBOL(fbtft_remove_common);
  
  MODULE_LICENSE("GPL");
  