WSL2-Linux-Kernel/arch/x86/kernel/sysfb_simplefb.c

/*
 * Generic System Framebuffers on x86
 * Copyright (c) 2012-2013 David Herrmann <dh.herrmann@gmail.com>
 *
 * 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.
 */

/*
 * simple-framebuffer probing
 * Try to convert "screen_info" into a "simple-framebuffer" compatible mode.
 * If the mode is incompatible, we return "false" and let the caller create
 * legacy nodes instead.
 */

#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/platform_data/simplefb.h>
#include <linux/platform_device.h>
#include <linux/screen_info.h>
#include <asm/sysfb.h>

static const char simplefb_resname[] = "BOOTFB";
static const struct simplefb_format formats[] = SIMPLEFB_FORMATS;

/* try parsing x86 screen_info into a simple-framebuffer mode struct */
__init bool parse_mode(const struct screen_info *si,
		       struct simplefb_platform_data *mode)
{
	const struct simplefb_format *f;
	__u8 type;
	unsigned int i;

	type = si->orig_video_isVGA;
	if (type != VIDEO_TYPE_VLFB && type != VIDEO_TYPE_EFI)
		return false;

	for (i = 0; i < ARRAY_SIZE(formats); ++i) {
		f = &formats[i];
		if (si->lfb_depth == f->bits_per_pixel &&
		    si->red_size == f->red.length &&
		    si->red_pos == f->red.offset &&
		    si->green_size == f->green.length &&
		    si->green_pos == f->green.offset &&
		    si->blue_size == f->blue.length &&
		    si->blue_pos == f->blue.offset &&
		    si->rsvd_size == f->transp.length &&
		    si->rsvd_pos == f->transp.offset) {
			mode->format = f->name;
			mode->width = si->lfb_width;
			mode->height = si->lfb_height;
			mode->stride = si->lfb_linelength;
			return true;
		}
	}

	return false;
}

__init int create_simplefb(const struct screen_info *si,
			   const struct simplefb_platform_data *mode)
{
	struct platform_device *pd;
	struct resource res;
	unsigned long len;

	/* don't use lfb_size as it may contain the whole VMEM instead of only
	 * the part that is occupied by the framebuffer */
	len = mode->height * mode->stride;
	len = PAGE_ALIGN(len);
	if (len > (u64)si->lfb_size << 16) {
		printk(KERN_WARNING "sysfb: VRAM smaller than advertised\n");
		return -EINVAL;
	}

	/* setup IORESOURCE_MEM as framebuffer memory */
	memset(&res, 0, sizeof(res));
	res.flags = IORESOURCE_MEM | IORESOURCE_BUSY;
	res.name = simplefb_resname;
	res.start = si->lfb_base;
	res.end = si->lfb_base + len - 1;
	if (res.end <= res.start)
		return -EINVAL;

	pd = platform_device_register_resndata(NULL, "simple-framebuffer", 0,
					       &res, 1, mode, sizeof(*mode));
	if (IS_ERR(pd))
		return PTR_ERR(pd);

	return 0;
}