linux/drivers/video/simplefb.c
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   1/*
   2 * Simplest possible simple frame-buffer driver, as a platform device
   3 *
   4 * Copyright (c) 2013, Stephen Warren
   5 *
   6 * Based on q40fb.c, which was:
   7 * Copyright (C) 2001 Richard Zidlicky <rz@linux-m68k.org>
   8 *
   9 * Also based on offb.c, which was:
  10 * Copyright (C) 1997 Geert Uytterhoeven
  11 * Copyright (C) 1996 Paul Mackerras
  12 *
  13 * This program is free software; you can redistribute it and/or modify it
  14 * under the terms and conditions of the GNU General Public License,
  15 * version 2, as published by the Free Software Foundation.
  16 *
  17 * This program is distributed in the hope it will be useful, but WITHOUT
  18 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  19 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  20 * more details.
  21 */
  22
  23#include <linux/errno.h>
  24#include <linux/fb.h>
  25#include <linux/io.h>
  26#include <linux/module.h>
  27#include <linux/platform_device.h>
  28
  29static struct fb_fix_screeninfo simplefb_fix = {
  30        .id             = "simple",
  31        .type           = FB_TYPE_PACKED_PIXELS,
  32        .visual         = FB_VISUAL_TRUECOLOR,
  33        .accel          = FB_ACCEL_NONE,
  34};
  35
  36static struct fb_var_screeninfo simplefb_var = {
  37        .height         = -1,
  38        .width          = -1,
  39        .activate       = FB_ACTIVATE_NOW,
  40        .vmode          = FB_VMODE_NONINTERLACED,
  41};
  42
  43static int simplefb_setcolreg(u_int regno, u_int red, u_int green, u_int blue,
  44                              u_int transp, struct fb_info *info)
  45{
  46        u32 *pal = info->pseudo_palette;
  47        u32 cr = red >> (16 - info->var.red.length);
  48        u32 cg = green >> (16 - info->var.green.length);
  49        u32 cb = blue >> (16 - info->var.blue.length);
  50        u32 value;
  51
  52        if (regno >= 16)
  53                return -EINVAL;
  54
  55        value = (cr << info->var.red.offset) |
  56                (cg << info->var.green.offset) |
  57                (cb << info->var.blue.offset);
  58        if (info->var.transp.length > 0) {
  59                u32 mask = (1 << info->var.transp.length) - 1;
  60                mask <<= info->var.transp.offset;
  61                value |= mask;
  62        }
  63        pal[regno] = value;
  64
  65        return 0;
  66}
  67
  68static struct fb_ops simplefb_ops = {
  69        .owner          = THIS_MODULE,
  70        .fb_setcolreg   = simplefb_setcolreg,
  71        .fb_fillrect    = cfb_fillrect,
  72        .fb_copyarea    = cfb_copyarea,
  73        .fb_imageblit   = cfb_imageblit,
  74};
  75
  76struct simplefb_format {
  77        const char *name;
  78        u32 bits_per_pixel;
  79        struct fb_bitfield red;
  80        struct fb_bitfield green;
  81        struct fb_bitfield blue;
  82        struct fb_bitfield transp;
  83};
  84
  85static struct simplefb_format simplefb_formats[] = {
  86        { "r5g6b5", 16, {11, 5}, {5, 6}, {0, 5}, {0, 0} },
  87};
  88
  89struct simplefb_params {
  90        u32 width;
  91        u32 height;
  92        u32 stride;
  93        struct simplefb_format *format;
  94};
  95
  96static int simplefb_parse_dt(struct platform_device *pdev,
  97                           struct simplefb_params *params)
  98{
  99        struct device_node *np = pdev->dev.of_node;
 100        int ret;
 101        const char *format;
 102        int i;
 103
 104        ret = of_property_read_u32(np, "width", &params->width);
 105        if (ret) {
 106                dev_err(&pdev->dev, "Can't parse width property\n");
 107                return ret;
 108        }
 109
 110        ret = of_property_read_u32(np, "height", &params->height);
 111        if (ret) {
 112                dev_err(&pdev->dev, "Can't parse height property\n");
 113                return ret;
 114        }
 115
 116        ret = of_property_read_u32(np, "stride", &params->stride);
 117        if (ret) {
 118                dev_err(&pdev->dev, "Can't parse stride property\n");
 119                return ret;
 120        }
 121
 122        ret = of_property_read_string(np, "format", &format);
 123        if (ret) {
 124                dev_err(&pdev->dev, "Can't parse format property\n");
 125                return ret;
 126        }
 127        params->format = NULL;
 128        for (i = 0; i < ARRAY_SIZE(simplefb_formats); i++) {
 129                if (strcmp(format, simplefb_formats[i].name))
 130                        continue;
 131                params->format = &simplefb_formats[i];
 132                break;
 133        }
 134        if (!params->format) {
 135                dev_err(&pdev->dev, "Invalid format value\n");
 136                return -EINVAL;
 137        }
 138
 139        return 0;
 140}
 141
 142static int simplefb_probe(struct platform_device *pdev)
 143{
 144        int ret;
 145        struct simplefb_params params;
 146        struct fb_info *info;
 147        struct resource *mem;
 148
 149        if (fb_get_options("simplefb", NULL))
 150                return -ENODEV;
 151
 152        ret = simplefb_parse_dt(pdev, &params);
 153        if (ret)
 154                return ret;
 155
 156        mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 157        if (!mem) {
 158                dev_err(&pdev->dev, "No memory resource\n");
 159                return -EINVAL;
 160        }
 161
 162        info = framebuffer_alloc(sizeof(u32) * 16, &pdev->dev);
 163        if (!info)
 164                return -ENOMEM;
 165        platform_set_drvdata(pdev, info);
 166
 167        info->fix = simplefb_fix;
 168        info->fix.smem_start = mem->start;
 169        info->fix.smem_len = resource_size(mem);
 170        info->fix.line_length = params.stride;
 171
 172        info->var = simplefb_var;
 173        info->var.xres = params.width;
 174        info->var.yres = params.height;
 175        info->var.xres_virtual = params.width;
 176        info->var.yres_virtual = params.height;
 177        info->var.bits_per_pixel = params.format->bits_per_pixel;
 178        info->var.red = params.format->red;
 179        info->var.green = params.format->green;
 180        info->var.blue = params.format->blue;
 181        info->var.transp = params.format->transp;
 182
 183        info->fbops = &simplefb_ops;
 184        info->flags = FBINFO_DEFAULT;
 185        info->screen_base = devm_ioremap(&pdev->dev, info->fix.smem_start,
 186                                         info->fix.smem_len);
 187        if (!info->screen_base) {
 188                framebuffer_release(info);
 189                return -ENODEV;
 190        }
 191        info->pseudo_palette = (void *)(info + 1);
 192
 193        ret = register_framebuffer(info);
 194        if (ret < 0) {
 195                dev_err(&pdev->dev, "Unable to register simplefb: %d\n", ret);
 196                framebuffer_release(info);
 197                return ret;
 198        }
 199
 200        dev_info(&pdev->dev, "fb%d: simplefb registered!\n", info->node);
 201
 202        return 0;
 203}
 204
 205static int simplefb_remove(struct platform_device *pdev)
 206{
 207        struct fb_info *info = platform_get_drvdata(pdev);
 208
 209        unregister_framebuffer(info);
 210        framebuffer_release(info);
 211
 212        return 0;
 213}
 214
 215static const struct of_device_id simplefb_of_match[] = {
 216        { .compatible = "simple-framebuffer", },
 217        { },
 218};
 219MODULE_DEVICE_TABLE(of, simplefb_of_match);
 220
 221static struct platform_driver simplefb_driver = {
 222        .driver = {
 223                .name = "simple-framebuffer",
 224                .owner = THIS_MODULE,
 225                .of_match_table = simplefb_of_match,
 226        },
 227        .probe = simplefb_probe,
 228        .remove = simplefb_remove,
 229};
 230module_platform_driver(simplefb_driver);
 231
 232MODULE_AUTHOR("Stephen Warren <swarren@wwwdotorg.org>");
 233MODULE_DESCRIPTION("Simple framebuffer driver");
 234MODULE_LICENSE("GPL v2");
 235
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