text: #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/init.h>
  #include <linux/gpio.h>
  #include <linux/spi/spi.h>
  #include <linux/delay.h>
  
  #include "fbtft.h"
  
  #define DRVNAME		"fb_ssd1351"
  #define WIDTH		128
  #define HEIGHT		128
  #define GAMMA_NUM	1
  #define GAMMA_LEN	63
  #define DEFAULT_GAMMA	"0 2 2 2 2 2 2 2 " \
  			"2 2 2 2 2 2 2 2 " \
  			"2 2 2 2 2 2 2 2 " \
  			"2 2 2 2 2 2 2 2 " \
  			"2 2 2 2 2 2 2 2 " \
  			"2 2 2 2 2 2 2 2 " \
  			"2 2 2 2 2 2 2 2 " \
  			"2 2 2 2 2 2 2" \
  
  static void register_onboard_backlight(struct fbtft_par *par);
  
  static int init_display(struct fbtft_par *par)
  {
  	fbtft_par_dbg(DEBUG_INIT_DISPLAY, par, "%s()\n", __func__);
  
  	if (par->pdata
  		&& par->pdata->display.backlight == FBTFT_ONBOARD_BACKLIGHT) {
  		/* module uses onboard GPIO for panel power */
  		par->fbtftops.register_backlight = register_onboard_backlight;
  	}
  
  	par->fbtftops.reset(par);
  
  	write_reg(par, 0xfd, 0x12); /* Command Lock */
  	write_reg(par, 0xfd, 0xb1); /* Command Lock */
  	write_reg(par, 0xae); /* Display Off */
  	write_reg(par, 0xb3, 0xf1); /* Front Clock Div */
  	write_reg(par, 0xca, 0x7f); /* Set Mux Ratio */
  	write_reg(par, 0x15, 0x00, 0x7f); /* Set Column Address */
  	write_reg(par, 0x75, 0x00, 0x7f); /* Set Row Address */
  	write_reg(par, 0xa1, 0x00); /* Set Display Start Line */
  	write_reg(par, 0xa2, 0x00); /* Set Display Offset */
  	write_reg(par, 0xb5, 0x00); /* Set GPIO */
  	write_reg(par, 0xab, 0x01); /* Set Function Selection */
  	write_reg(par, 0xb1, 0x32); /* Set Phase Length */
  	write_reg(par, 0xb4, 0xa0, 0xb5, 0x55); /* Set Segment Low Voltage */
  	write_reg(par, 0xbb, 0x17); /* Set Precharge Voltage */
  	write_reg(par, 0xbe, 0x05); /* Set VComH Voltage */
  	write_reg(par, 0xc1, 0xc8, 0x80, 0xc8); /* Set Contrast */
  	write_reg(par, 0xc7, 0x0f); /* Set Master Contrast */
  	write_reg(par, 0xb6, 0x01); /* Set Second Precharge Period */
  	write_reg(par, 0xa6); /* Set Display Mode Reset */
  	write_reg(par, 0xaf); /* Set Sleep Mode Display On */
  
  	return 0;
  }
  
  static void set_addr_win(struct fbtft_par *par, int xs, int ys, int xe, int ye)
  {
  	fbtft_par_dbg(DEBUG_SET_ADDR_WIN, par,
  		"%s(xs=%d, ys=%d, xe=%d, ye=%d)\n", __func__, xs, ys, xe, ye);
  
  	write_reg(par, 0x15, xs, xe);
  	write_reg(par, 0x75, ys, ye);
  	write_reg(par, 0x5c);
  }
  
  static int set_var(struct fbtft_par *par)
  {
  	unsigned remap;
  	fbtft_par_dbg(DEBUG_INIT_DISPLAY, par, "%s()\n", __func__);
  
  	if (par->fbtftops.init_display != init_display) {
  		/* don't risk messing up register A0h */
  		fbtft_par_dbg(DEBUG_INIT_DISPLAY, par,
  			"%s: skipping since custom init_display() is used\n",
  			__func__);
  		return 0;
  	}
  
  	remap = 0x60 | (par->bgr << 2); /* Set Colour Depth */
  
  	switch (par->info->var.rotate) {
  	case 0:
  		write_reg(par, 0xA0, remap | 0b00 | 1<<4);
  		break;
  	case 270:
  		write_reg(par, 0xA0, remap | 0b11 | 1<<4);
  		break;
  	case 180:
  		write_reg(par, 0xA0, remap | 0b10);
  		break;
  	case 90:
  		write_reg(par, 0xA0, remap | 0b01);
  		break;
  	}
  
  	return 0;
  }
  
  /*
  	Grayscale Lookup Table
  	GS1 - GS63
  	The driver Gamma curve contains the relative values between the entries
  	in the Lookup table.
  
  	From datasheet:
  	8.8 Gray Scale Decoder
  
  		there are total 180 Gamma Settings (Setting 0 to Setting 180)
  		available for the Gray Scale table.
  
  		The gray scale is defined in incremental way, with reference
  		to the length of previous table entry:
  			Setting of GS1 has to be >= 0
  			Setting of GS2 has to be > Setting of GS1 +1
  			Setting of GS3 has to be > Setting of GS2 +1
  			:
  			Setting of GS63 has to be > Setting of GS62 +1
  
  
  */
  static int set_gamma(struct fbtft_par *par, unsigned long *curves)
  {
  	unsigned long tmp[GAMMA_NUM * GAMMA_LEN];
  	int i, acc = 0;
  
  	fbtft_par_dbg(DEBUG_INIT_DISPLAY, par, "%s()\n", __func__);
  
  	for (i = 0; i < 63; i++) {
  		if (i > 0 && curves[i] < 2) {
  			dev_err(par->info->device,
  				"Illegal value in Grayscale Lookup Table at index %d. " \
  				"Must be greater than 1\n", i);
  			return -EINVAL;
  		}
  		acc += curves[i];
  		tmp[i] = acc;
  		if (acc > 180) {
  			dev_err(par->info->device,
  				"Illegal value(s) in Grayscale Lookup Table. " \
  				"At index=%d, the accumulated value has exceeded 180\n", i);
  			return -EINVAL;
  		}
  	}
  
  	write_reg(par, 0xB8,
  	tmp[0], tmp[1], tmp[2], tmp[3], tmp[4], tmp[5], tmp[6], tmp[7],
  	tmp[8], tmp[9], tmp[10], tmp[11], tmp[12], tmp[13], tmp[14], tmp[15],
  	tmp[16], tmp[17], tmp[18], tmp[19], tmp[20], tmp[21], tmp[22], tmp[23],
  	tmp[24], tmp[25], tmp[26], tmp[27], tmp[28], tmp[29], tmp[30], tmp[31],
  	tmp[32], tmp[33], tmp[34], tmp[35], tmp[36], tmp[37], tmp[38], tmp[39],
  	tmp[40], tmp[41], tmp[42], tmp[43], tmp[44], tmp[45], tmp[46], tmp[47],
  	tmp[48], tmp[49], tmp[50], tmp[51], tmp[52], tmp[53], tmp[54], tmp[55],
  	tmp[56], tmp[57], tmp[58], tmp[59], tmp[60], tmp[61], tmp[62]);
  
  	return 0;
  }
  
  static int blank(struct fbtft_par *par, bool on)
  {
  	fbtft_par_dbg(DEBUG_BLANK, par, "%s(blank=%s)\n",
  		__func__, on ? "true" : "false");
  	if (on)
  		write_reg(par, 0xAE);
  	else
  		write_reg(par, 0xAF);
  	return 0;
  }
  
  
  static struct fbtft_display display = {
  	.regwidth = 8,
  	.width = WIDTH,
  	.height = HEIGHT,
  	.gamma_num = GAMMA_NUM,
  	.gamma_len = GAMMA_LEN,
  	.gamma = DEFAULT_GAMMA,
  	.fbtftops = {
  		.init_display = init_display,
  		.set_addr_win = set_addr_win,
  		.set_var = set_var,
  		.set_gamma = set_gamma,
  		.blank = blank,
  	},
  };
  
  #ifdef CONFIG_FB_BACKLIGHT
  static int update_onboard_backlight(struct backlight_device *bd)
  {
  	struct fbtft_par *par = bl_get_data(bd);
  	bool on;
  
  	fbtft_par_dbg(DEBUG_BACKLIGHT, par,
  		"%s: power=%d, fb_blank=%d\n",
  		__func__, bd->props.power, bd->props.fb_blank);
  
  	on = (bd->props.power == FB_BLANK_UNBLANK)
  		&& (bd->props.fb_blank == FB_BLANK_UNBLANK);
  	/* Onboard backlight connected to GPIO0 on SSD1351, GPIO1 unused */
  	write_reg(par, 0xB5, on ? 0x03 : 0x02);
  
  	return 0;
  }
  
  static void register_onboard_backlight(struct fbtft_par *par)
  {
  	struct backlight_device *bd;
  	struct backlight_properties bl_props = { 0, };
  	struct backlight_ops *bl_ops;
  
  	fbtft_par_dbg(DEBUG_BACKLIGHT, par, "%s()\n", __func__);
  
  	bl_ops = devm_kzalloc(par->info->device, sizeof(struct backlight_ops),
  				GFP_KERNEL);
  	if (!bl_ops) {
  		dev_err(par->info->device,
  			"%s: could not allocate memory for backlight operations.\n",
  			__func__);
  		return;
  	}
  
  	bl_ops->update_status = update_onboard_backlight;
  	bl_props.type = BACKLIGHT_RAW;
  	bl_props.power = FB_BLANK_POWERDOWN;
  
  	bd = backlight_device_register(dev_driver_string(par->info->device),
  				par->info->device, par, 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
  static void register_onboard_backlight(struct fbtft_par *par) { };
  #endif
  
  
  FBTFT_REGISTER_DRIVER(DRVNAME, "solomon,ssd1351", &display);
  
  MODULE_ALIAS("spi:" DRVNAME);
  MODULE_ALIAS("platform:" DRVNAME);
  MODULE_ALIAS("spi:ssd1351");
  MODULE_ALIAS("platform:ssd1351");
  
  MODULE_DESCRIPTION("SSD1351 OLED Driver");
  MODULE_AUTHOR("James Davies");
  MODULE_LICENSE("GPL");
  