1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * Generic System Framebuffers
  4 * Copyright (c) 2012-2013 David Herrmann <dh.herrmann@gmail.com>
  5 */
  6
  7/*
  8 * simple-framebuffer probing
  9 * Try to convert "screen_info" into a "simple-framebuffer" compatible mode.
 10 * If the mode is incompatible, we return "false" and let the caller create
 11 * legacy nodes instead.
 12 */
 13
 14#include <linux/err.h>
 15#include <linux/init.h>
 16#include <linux/kernel.h>
 17#include <linux/mm.h>
 18#include <linux/platform_data/simplefb.h>
 19#include <linux/platform_device.h>
 20#include <linux/screen_info.h>
 21#include <linux/sysfb.h>
 22
 23static const char simplefb_resname[] = "BOOTFB";
 24static const struct simplefb_format formats[] = SIMPLEFB_FORMATS;
 25
 26/* try parsing screen_info into a simple-framebuffer mode struct */
 27__init bool sysfb_parse_mode(const struct screen_info *si,
 28			     struct simplefb_platform_data *mode)
 29{
 30	__u8 type;
 31	u32 bits_per_pixel;
 32	unsigned int i;
 33
 34	type = si->orig_video_isVGA;
 35	if (type != VIDEO_TYPE_VLFB && type != VIDEO_TYPE_EFI)
 36		return false;
 37
 38	/*
 39	 * The meaning of depth and bpp for direct-color formats is
 40	 * inconsistent:
 41	 *
 42	 *  - DRM format info specifies depth as the number of color
 43	 *    bits; including alpha, but not including filler bits.
 44	 *  - Linux' EFI platform code computes lfb_depth from the
 45	 *    individual color channels, including the reserved bits.
 46	 *  - VBE 1.1 defines lfb_depth for XRGB1555 as 16, but later
 47	 *    versions use 15.
 48	 *  - On the kernel command line, 'bpp' of 32 is usually
 49	 *    XRGB8888 including the filler bits, but 15 is XRGB1555
 50	 *    not including the filler bit.
 51	 *
 52	 * It's not easily possible to fix this in struct screen_info,
 53	 * as this could break UAPI. The best solution is to compute
 54	 * bits_per_pixel from the color bits, reserved bits and
 55	 * reported lfb_depth, whichever is highest.  In the loop below,
 56	 * ignore simplefb formats with alpha bits, as EFI and VESA
 57	 * don't specify alpha channels.
 58	 */
 59	if (si->lfb_depth > 8) {
 60		bits_per_pixel = max(max3(si->red_size + si->red_pos,
 61					  si->green_size + si->green_pos,
 62					  si->blue_size + si->blue_pos),
 63				     si->rsvd_size + si->rsvd_pos);
 64		bits_per_pixel = max_t(u32, bits_per_pixel, si->lfb_depth);
 65	} else {
 66		bits_per_pixel = si->lfb_depth;
 67	}
 68
 69	for (i = 0; i < ARRAY_SIZE(formats); ++i) {
 70		const struct simplefb_format *f = &formats[i];
 71
 72		if (f->transp.length)
 73			continue; /* transparent formats are unsupported by VESA/EFI */
 74
 75		if (bits_per_pixel == f->bits_per_pixel &&
 76		    si->red_size == f->red.length &&
 77		    si->red_pos == f->red.offset &&
 78		    si->green_size == f->green.length &&
 79		    si->green_pos == f->green.offset &&
 80		    si->blue_size == f->blue.length &&
 81		    si->blue_pos == f->blue.offset) {
 82			mode->format = f->name;
 83			mode->width = si->lfb_width;
 84			mode->height = si->lfb_height;
 85			mode->stride = si->lfb_linelength;
 86			return true;
 87		}
 88	}
 89
 90	return false;
 91}
 92
 93__init struct platform_device *sysfb_create_simplefb(const struct screen_info *si,
 94						     const struct simplefb_platform_data *mode,
 95						     struct device *parent)
 96{
 97	struct platform_device *pd;
 98	struct resource res;
 99	u64 base, size;
100	u32 length;
101	int ret;
102
103	/*
104	 * If the 64BIT_BASE capability is set, ext_lfb_base will contain the
105	 * upper half of the base address. Assemble the address, then make sure
106	 * it is valid and we can actually access it.
107	 */
108	base = si->lfb_base;
109	if (si->capabilities & VIDEO_CAPABILITY_64BIT_BASE)
110		base |= (u64)si->ext_lfb_base << 32;
111	if (!base || (u64)(resource_size_t)base != base) {
112		printk(KERN_DEBUG "sysfb: inaccessible VRAM base\n");
113		return ERR_PTR(-EINVAL);
114	}
115
116	/*
117	 * Don't use lfb_size as IORESOURCE size, since it may contain the
118	 * entire VMEM, and thus require huge mappings. Use just the part we
119	 * need, that is, the part where the framebuffer is located. But verify
120	 * that it does not exceed the advertised VMEM.
121	 * Note that in case of VBE, the lfb_size is shifted by 16 bits for
122	 * historical reasons.
123	 */
124	size = si->lfb_size;
125	if (si->orig_video_isVGA == VIDEO_TYPE_VLFB)
126		size <<= 16;
127	length = mode->height * mode->stride;
128	if (length > size) {
129		printk(KERN_WARNING "sysfb: VRAM smaller than advertised\n");
130		return ERR_PTR(-EINVAL);
131	}
132	length = PAGE_ALIGN(length);
133
134	/* setup IORESOURCE_MEM as framebuffer memory */
135	memset(&res, 0, sizeof(res));
136	res.flags = IORESOURCE_MEM;
137	res.name = simplefb_resname;
138	res.start = base;
139	res.end = res.start + length - 1;
140	if (res.end <= res.start)
141		return ERR_PTR(-EINVAL);
142
143	pd = platform_device_alloc("simple-framebuffer", 0);
144	if (!pd)
145		return ERR_PTR(-ENOMEM);
146
147	pd->dev.parent = parent;
148
149	sysfb_set_efifb_fwnode(pd);
150
151	ret = platform_device_add_resources(pd, &res, 1);
152	if (ret)
153		goto err_put_device;
154
155	ret = platform_device_add_data(pd, mode, sizeof(*mode));
156	if (ret)
157		goto err_put_device;
158
159	ret = platform_device_add(pd);
160	if (ret)
161		goto err_put_device;
162
163	return pd;
164
165err_put_device:
166	platform_device_put(pd);
167
168	return ERR_PTR(ret);
169}