// SPDX-License-Identifier: GPL-2.0 or MIT
/*
 * Copyright (c) 2023 Red Hat.
 * Author: Jocelyn Falempe <jfalempe@redhat.com>
 * inspired by the drm_log driver from David Herrmann <dh.herrmann@gmail.com>
 * Tux Ascii art taken from cowsay written by Tony Monroe
 */

#include <linux/export.h>
#include <linux/font.h>
#include <linux/highmem.h>
#include <linux/init.h>
#include <linux/iosys-map.h>
#include <linux/kdebug.h>
#include <linux/kmsg_dump.h>
#include <linux/linux_logo.h>
#include <linux/list.h>
#include <linux/math.h>
#include <linux/module.h>
#include <linux/overflow.h>
#include <linux/printk.h>
#include <linux/types.h>
#include <linux/utsname.h>
#include <linux/zlib.h>

#include <drm/drm_drv.h>
#include <drm/drm_fourcc.h>
#include <drm/drm_framebuffer.h>
#include <drm/drm_modeset_helper_vtables.h>
#include <drm/drm_panic.h>
#include <drm/drm_plane.h>
#include <drm/drm_print.h>
#include <drm/drm_rect.h>

#include "drm_crtc_internal.h"
#include "drm_draw_internal.h"

MODULE_AUTHOR("Jocelyn Falempe");
MODULE_DESCRIPTION("DRM panic handler");
MODULE_LICENSE("GPL");

static char drm_panic_screen[16] = CONFIG_DRM_PANIC_SCREEN;
module_param_string(panic_screen, drm_panic_screen, sizeof(drm_panic_screen), 0644);
MODULE_PARM_DESC(panic_screen,
                 "Choose what will be displayed by drm_panic, 'user' or 'kmsg' [default="
                 CONFIG_DRM_PANIC_SCREEN "]");

/**
 * DOC: overview
 *
 * To enable DRM panic for a driver, the primary plane must implement a
 * &drm_plane_helper_funcs.get_scanout_buffer helper function. It is then
 * automatically registered to the drm panic handler.
 * When a panic occurs, the &drm_plane_helper_funcs.get_scanout_buffer will be
 * called, and the driver can provide a framebuffer so the panic handler can
 * draw the panic screen on it. Currently only linear buffer and a few color
 * formats are supported.
 * Optionally the driver can also provide a &drm_plane_helper_funcs.panic_flush
 * callback, that will be called after that, to send additional commands to the
 * hardware to make the scanout buffer visible.
 */

/*
 * This module displays a user friendly message on screen when a kernel panic
 * occurs. This is conflicting with fbcon, so you can only enable it when fbcon
 * is disabled.
 * It's intended for end-user, so have minimal technical/debug information.
 *
 * Implementation details:
 *
 * It is a panic handler, so it can't take lock, allocate memory, run tasks/irq,
 * or attempt to sleep. It's a best effort, and it may not be able to display
 * the message in all situations (like if the panic occurs in the middle of a
 * modesetting).
 * It will display only one static frame, so performance optimizations are low
 * priority as the machine is already in an unusable state.
 */

struct drm_panic_line {
        u32 len;
        const char *txt;
};

#define PANIC_LINE(s) {.len = sizeof(s) - 1, .txt = s}

static struct drm_panic_line panic_msg[] = {
        PANIC_LINE("KERNEL PANIC!"),
        PANIC_LINE(""),
        PANIC_LINE("Please reboot your computer."),
        PANIC_LINE(""),
        PANIC_LINE(""), /* will be replaced by the panic description */
};

static const size_t panic_msg_lines = ARRAY_SIZE(panic_msg);

static const struct drm_panic_line logo_ascii[] = {
        PANIC_LINE("     .--.        _"),
        PANIC_LINE("    |o_o |      | |"),
        PANIC_LINE("    |:_/ |      | |"),
        PANIC_LINE("   //   \\ \\     |_|"),
        PANIC_LINE("  (|     | )     _"),
        PANIC_LINE(" /'\\_   _/`\\    (_)"),
        PANIC_LINE(" \\___)=(___/"),
};

static const size_t logo_ascii_lines = ARRAY_SIZE(logo_ascii);

#if defined(CONFIG_LOGO) && !defined(MODULE)
static const struct linux_logo *logo_mono;

static int drm_panic_setup_logo(void)
{
        const struct linux_logo *logo = fb_find_logo(1);
        const unsigned char *logo_data;
        struct linux_logo *logo_dup;

        if (!logo || logo->type != LINUX_LOGO_MONO)
                return 0;

        /* The logo is __init, so we must make a copy for later use */
        logo_data = kmemdup(logo->data,
                            size_mul(DIV_ROUND_UP(logo->width, BITS_PER_BYTE), logo->height),
                            GFP_KERNEL);
        if (!logo_data)
                return -ENOMEM;

        logo_dup = kmemdup(logo, sizeof(*logo), GFP_KERNEL);
        if (!logo_dup) {
                kfree(logo_data);
                return -ENOMEM;
        }

        logo_dup->data = logo_data;
        logo_mono = logo_dup;

        return 0;
}

device_initcall(drm_panic_setup_logo);
#else
#define logo_mono       ((const struct linux_logo *)NULL)
#endif

/*
 *  Blit & Fill functions
 */
static void drm_panic_blit_pixel(struct drm_scanout_buffer *sb, struct drm_rect *clip,
                                 const u8 *sbuf8, unsigned int spitch, unsigned int scale,
                                 u32 fg_color)
{
        unsigned int y, x;

        for (y = 0; y < drm_rect_height(clip); y++)
                for (x = 0; x < drm_rect_width(clip); x++)
                        if (drm_draw_is_pixel_fg(sbuf8, spitch, x / scale, y / scale))
                                sb->set_pixel(sb, clip->x1 + x, clip->y1 + y, fg_color);
}

static void drm_panic_write_pixel16(void *vaddr, unsigned int offset, u16 color)
{
        u16 *p = vaddr + offset;

        *p = color;
}

static void drm_panic_write_pixel24(void *vaddr, unsigned int offset, u32 color)
{
        u8 *p = vaddr + offset;

        *p++ = color & 0xff;
        color >>= 8;
        *p++ = color & 0xff;
        color >>= 8;
        *p = color & 0xff;
}

/*
 * Special case if the pixel crosses page boundaries
 */
static void drm_panic_write_pixel24_xpage(void *vaddr, struct page *next_page,
                                          unsigned int offset, u32 color)
{
        u8 *vaddr2;
        u8 *p = vaddr + offset;

        vaddr2 = kmap_local_page_try_from_panic(next_page);

        *p++ = color & 0xff;
        color >>= 8;

        if (offset == PAGE_SIZE - 1)
                p = vaddr2;

        *p++ = color & 0xff;
        color >>= 8;

        if (offset == PAGE_SIZE - 2)
                p = vaddr2;

        *p = color & 0xff;
        kunmap_local(vaddr2);
}

static void drm_panic_write_pixel32(void *vaddr, unsigned int offset, u32 color)
{
        u32 *p = vaddr + offset;

        *p = color;
}

static void drm_panic_write_pixel(void *vaddr, unsigned int offset, u32 color, unsigned int cpp)
{
        switch (cpp) {
        case 2:
                drm_panic_write_pixel16(vaddr, offset, color);
                break;
        case 3:
                drm_panic_write_pixel24(vaddr, offset, color);
                break;
        case 4:
                drm_panic_write_pixel32(vaddr, offset, color);
                break;
        default:
                pr_debug_once("Can't blit with pixel width %d\n", cpp);
        }
}

/*
 * The scanout buffer pages are not mapped, so for each pixel,
 * use kmap_local_page_try_from_panic() to map the page, and write the pixel.
 * Try to keep the map from the previous pixel, to avoid too much map/unmap.
 */
static void drm_panic_blit_page(struct page **pages, unsigned int dpitch,
                                unsigned int cpp, const u8 *sbuf8,
                                unsigned int spitch, struct drm_rect *clip,
                                unsigned int scale, u32 fg32)
{
        unsigned int y, x;
        unsigned int page = ~0;
        unsigned int height = drm_rect_height(clip);
        unsigned int width = drm_rect_width(clip);
        void *vaddr = NULL;

        for (y = 0; y < height; y++) {
                for (x = 0; x < width; x++) {
                        if (drm_draw_is_pixel_fg(sbuf8, spitch, x / scale, y / scale)) {
                                unsigned int new_page;
                                unsigned int offset;

                                offset = (y + clip->y1) * dpitch + (x + clip->x1) * cpp;
                                new_page = offset >> PAGE_SHIFT;
                                offset = offset % PAGE_SIZE;
                                if (new_page != page) {
                                        if (!pages[new_page])
                                                continue;
                                        if (vaddr)
                                                kunmap_local(vaddr);
                                        page = new_page;
                                        vaddr = kmap_local_page_try_from_panic(pages[page]);
                                }
                                if (!vaddr)
                                        continue;

                                // Special case for 24bit, as a pixel might cross page boundaries
                                if (cpp == 3 && offset + 3 > PAGE_SIZE)
                                        drm_panic_write_pixel24_xpage(vaddr, pages[page + 1],
                                                                      offset, fg32);
                                else
                                        drm_panic_write_pixel(vaddr, offset, fg32, cpp);
                        }
                }
        }
        if (vaddr)
                kunmap_local(vaddr);
}

/*
 * drm_panic_blit - convert a monochrome image to a linear framebuffer
 * @sb: destination scanout buffer
 * @clip: destination rectangle
 * @sbuf8: source buffer, in monochrome format, 8 pixels per byte.
 * @spitch: source pitch in bytes
 * @scale: integer scale, source buffer is scale time smaller than destination
 *         rectangle
 * @fg_color: foreground color, in destination format
 *
 * This can be used to draw a font character, which is a monochrome image, to a
 * framebuffer in other supported format.
 */
static void drm_panic_blit(struct drm_scanout_buffer *sb, struct drm_rect *clip,
                           const u8 *sbuf8, unsigned int spitch,
                           unsigned int scale, u32 fg_color)

{
        struct iosys_map map;

        if (sb->set_pixel)
                return drm_panic_blit_pixel(sb, clip, sbuf8, spitch, scale, fg_color);

        if (sb->pages)
                return drm_panic_blit_page(sb->pages, sb->pitch[0], sb->format->cpp[0],
                                           sbuf8, spitch, clip, scale, fg_color);

        map = sb->map[0];
        iosys_map_incr(&map, clip->y1 * sb->pitch[0] + clip->x1 * sb->format->cpp[0]);

        switch (sb->format->cpp[0]) {
        case 2:
                drm_draw_blit16(&map, sb->pitch[0], sbuf8, spitch,
                                drm_rect_height(clip), drm_rect_width(clip), scale, fg_color);
        break;
        case 3:
                drm_draw_blit24(&map, sb->pitch[0], sbuf8, spitch,
                                drm_rect_height(clip), drm_rect_width(clip), scale, fg_color);
        break;
        case 4:
                drm_draw_blit32(&map, sb->pitch[0], sbuf8, spitch,
                                drm_rect_height(clip), drm_rect_width(clip), scale, fg_color);
        break;
        default:
                WARN_ONCE(1, "Can't blit with pixel width %d\n", sb->format->cpp[0]);
        }
}

static void drm_panic_fill_pixel(struct drm_scanout_buffer *sb,
                                 struct drm_rect *clip,
                                 u32 color)
{
        unsigned int y, x;

        for (y = 0; y < drm_rect_height(clip); y++)
                for (x = 0; x < drm_rect_width(clip); x++)
                        sb->set_pixel(sb, clip->x1 + x, clip->y1 + y, color);
}

static void drm_panic_fill_page(struct page **pages, unsigned int dpitch,
                                unsigned int cpp, struct drm_rect *clip,
                                u32 color)
{
        unsigned int y, x;
        unsigned int page = ~0;
        void *vaddr = NULL;

        for (y = clip->y1; y < clip->y2; y++) {
                for (x = clip->x1; x < clip->x2; x++) {
                        unsigned int new_page;
                        unsigned int offset;

                        offset = y * dpitch + x * cpp;
                        new_page = offset >> PAGE_SHIFT;
                        offset = offset % PAGE_SIZE;
                        if (new_page != page) {
                                if (vaddr)
                                        kunmap_local(vaddr);
                                page = new_page;
                                vaddr = kmap_local_page_try_from_panic(pages[page]);
                        }
                        if (!vaddr)
                                continue;

                        // Special case for 24bit, as a pixel might cross page boundaries
                        if (cpp == 3 && offset + 3 > PAGE_SIZE)
                                drm_panic_write_pixel24_xpage(vaddr, pages[page + 1],
                                                              offset, color);
                        else
                                drm_panic_write_pixel(vaddr, offset, color, cpp);
                }
        }
        if (vaddr)
                kunmap_local(vaddr);
}

/*
 * drm_panic_fill - Fill a rectangle with a color
 * @sb: destination scanout buffer
 * @clip: destination rectangle
 * @color: foreground color, in destination format
 *
 * Fill a rectangle with a color, in a linear framebuffer.
 */
static void drm_panic_fill(struct drm_scanout_buffer *sb, struct drm_rect *clip,
                           u32 color)
{
        struct iosys_map map;

        if (sb->set_pixel)
                return drm_panic_fill_pixel(sb, clip, color);

        if (sb->pages)
                return drm_panic_fill_page(sb->pages, sb->pitch[0], sb->format->cpp[0],
                                           clip, color);

        map = sb->map[0];
        iosys_map_incr(&map, clip->y1 * sb->pitch[0] + clip->x1 * sb->format->cpp[0]);

        switch (sb->format->cpp[0]) {
        case 2:
                drm_draw_fill16(&map, sb->pitch[0], drm_rect_height(clip),
                                drm_rect_width(clip), color);
        break;
        case 3:
                drm_draw_fill24(&map, sb->pitch[0], drm_rect_height(clip),
                                drm_rect_width(clip), color);
        break;
        case 4:
                drm_draw_fill32(&map, sb->pitch[0], drm_rect_height(clip),
                                drm_rect_width(clip), color);
        break;
        default:
                WARN_ONCE(1, "Can't fill with pixel width %d\n", sb->format->cpp[0]);
        }
}

static unsigned int get_max_line_len(const struct drm_panic_line *lines, int len)
{
        int i;
        unsigned int max = 0;

        for (i = 0; i < len; i++)
                max = max(lines[i].len, max);
        return max;
}

/*
 * Draw a text in a rectangle on a framebuffer. The text is truncated if it overflows the rectangle
 */
static void draw_txt_rectangle(struct drm_scanout_buffer *sb,
                               const struct font_desc *font,
                               const struct drm_panic_line *msg,
                               unsigned int msg_lines,
                               bool centered,
                               struct drm_rect *clip,
                               u32 color)
{
        int i, j;
        const u8 *src;
        size_t font_pitch = DIV_ROUND_UP(font->width, 8);
        struct drm_rect rec;

        msg_lines = min(msg_lines,  drm_rect_height(clip) / font->height);
        for (i = 0; i < msg_lines; i++) {
                size_t line_len = min(msg[i].len, drm_rect_width(clip) / font->width);

                rec.y1 = clip->y1 +  i * font->height;
                rec.y2 = rec.y1 + font->height;
                rec.x1 = clip->x1;

                if (centered)
                        rec.x1 += (drm_rect_width(clip) - (line_len * font->width)) / 2;

                for (j = 0; j < line_len; j++) {
                        src = drm_draw_get_char_bitmap(font, msg[i].txt[j], font_pitch);
                        rec.x2 = rec.x1 + font->width;
                        drm_panic_blit(sb, &rec, src, font_pitch, 1, color);
                        rec.x1 += font->width;
                }
        }
}

static void drm_panic_logo_rect(struct drm_rect *rect, const struct font_desc *font)
{
        if (logo_mono) {
                drm_rect_init(rect, 0, 0, logo_mono->width, logo_mono->height);
        } else {
                int logo_width = get_max_line_len(logo_ascii, logo_ascii_lines) * font->width;

                drm_rect_init(rect, 0, 0, logo_width, logo_ascii_lines * font->height);
        }
}

static void drm_panic_logo_draw(struct drm_scanout_buffer *sb, struct drm_rect *rect,
                                const struct font_desc *font, u32 fg_color)
{
        if (rect->x2 > sb->width || rect->y2 > sb->height)
                return;

        if (logo_mono)
                drm_panic_blit(sb, rect, logo_mono->data,
                               DIV_ROUND_UP(drm_rect_width(rect), 8), 1, fg_color);
        else
                draw_txt_rectangle(sb, font, logo_ascii, logo_ascii_lines, false, rect,
                                   fg_color);
}

static void draw_panic_static_user(struct drm_scanout_buffer *sb)
{
        u32 fg_color = drm_draw_color_from_xrgb8888(CONFIG_DRM_PANIC_FOREGROUND_COLOR,
                                                    sb->format->format);
        u32 bg_color = drm_draw_color_from_xrgb8888(CONFIG_DRM_PANIC_BACKGROUND_COLOR,
                                                    sb->format->format);
        const struct font_desc *font = get_default_font(sb->width, sb->height, NULL, NULL);
        struct drm_rect r_screen, r_logo, r_msg;
        unsigned int msg_width, msg_height;

        if (!font)
                return;

        r_screen = DRM_RECT_INIT(0, 0, sb->width, sb->height);
        drm_panic_logo_rect(&r_logo, font);

        msg_width = min(get_max_line_len(panic_msg, panic_msg_lines) * font->width, sb->width);
        msg_height = min(panic_msg_lines * font->height, sb->height);
        r_msg = DRM_RECT_INIT(0, 0, msg_width, msg_height);

        /* Center the panic message */
        drm_rect_translate(&r_msg, (sb->width - r_msg.x2) / 2, (sb->height - r_msg.y2) / 2);

        /* Fill with the background color, and draw text on top */
        drm_panic_fill(sb, &r_screen, bg_color);

        if (!drm_rect_overlap(&r_logo, &r_msg))
                drm_panic_logo_draw(sb, &r_logo, font, fg_color);

        draw_txt_rectangle(sb, font, panic_msg, panic_msg_lines, true, &r_msg, fg_color);
}

/*
 * Draw one line of kmsg, and handle wrapping if it won't fit in the screen width.
 * Return the y-offset of the next line.
 */
static int draw_line_with_wrap(struct drm_scanout_buffer *sb, const struct font_desc *font,
                               struct drm_panic_line *line, int yoffset, u32 fg_color)
{
        int chars_per_row = sb->width / font->width;
        struct drm_rect r_txt = DRM_RECT_INIT(0, yoffset, sb->width, font->height);
        struct drm_panic_line line_wrap;

        if (line->len > chars_per_row) {
                line_wrap.len = line->len % chars_per_row;
                line_wrap.txt = line->txt + line->len - line_wrap.len;
                draw_txt_rectangle(sb, font, &line_wrap, 1, false, &r_txt, fg_color);
                r_txt.y1 -= font->height;
                if (r_txt.y1 < 0)
                        return r_txt.y1;
                while (line_wrap.txt > line->txt) {
                        line_wrap.txt -= chars_per_row;
                        line_wrap.len = chars_per_row;
                        draw_txt_rectangle(sb, font, &line_wrap, 1, false, &r_txt, fg_color);
                        r_txt.y1 -= font->height;
                        if (r_txt.y1 < 0)
                                return r_txt.y1;
                }
        } else {
                draw_txt_rectangle(sb, font, line, 1, false, &r_txt, fg_color);
                r_txt.y1 -= font->height;
        }
        return r_txt.y1;
}

/*
 * Draw the kmsg buffer to the screen, starting from the youngest message at the bottom,
 * and going up until reaching the top of the screen.
 */
static void draw_panic_static_kmsg(struct drm_scanout_buffer *sb)
{
        u32 fg_color = drm_draw_color_from_xrgb8888(CONFIG_DRM_PANIC_FOREGROUND_COLOR,
                                                    sb->format->format);
        u32 bg_color = drm_draw_color_from_xrgb8888(CONFIG_DRM_PANIC_BACKGROUND_COLOR,
                                                    sb->format->format);
        const struct font_desc *font = get_default_font(sb->width, sb->height, NULL, NULL);
        struct drm_rect r_screen = DRM_RECT_INIT(0, 0, sb->width, sb->height);
        struct kmsg_dump_iter iter;
        char kmsg_buf[512];
        size_t kmsg_len;
        struct drm_panic_line line;
        int yoffset;

        if (!font || font->width > sb->width)
                return;

        yoffset = sb->height - font->height - (sb->height % font->height) / 2;

        /* Fill with the background color, and draw text on top */
        drm_panic_fill(sb, &r_screen, bg_color);

        kmsg_dump_rewind(&iter);
        while (kmsg_dump_get_buffer(&iter, false, kmsg_buf, sizeof(kmsg_buf), &kmsg_len)) {
                char *start;
                char *end;

                /* ignore terminating NUL and newline */
                start = kmsg_buf + kmsg_len - 2;
                end = kmsg_buf + kmsg_len - 1;
                while (start > kmsg_buf && yoffset >= 0) {
                        while (start > kmsg_buf && *start != '\n')
                                start--;
                        /* don't count the newline character */
                        line.txt = start + (start == kmsg_buf ? 0 : 1);
                        line.len = end - line.txt;

                        yoffset = draw_line_with_wrap(sb, font, &line, yoffset, fg_color);
                        end = start;
                        start--;
                }
        }
}

#if defined(CONFIG_DRM_PANIC_SCREEN_QR_CODE)
/*
 * It is unwise to allocate memory in the panic callback, so the buffers are
 * pre-allocated. Only 2 buffers and the zlib workspace are needed.
 * Two buffers are enough, using the following buffer usage:
 * 1) kmsg messages are dumped in buffer1
 * 2) kmsg is zlib-compressed into buffer2
 * 3) compressed kmsg is encoded as QR-code Numeric stream in buffer1
 * 4) QR-code image is generated in buffer2
 * The Max QR code size is V40, 177x177, 4071 bytes for image, 2956 bytes for
 * data segments.
 *
 * Typically, ~7500 bytes of kmsg, are compressed into 2800 bytes, which fits in
 * a V40 QR-code (177x177).
 *
 * If CONFIG_DRM_PANIC_SCREEN_QR_CODE_URL is not set, the kmsg data will be put
 * directly in the QR code.
 * 1) kmsg messages are dumped in buffer1
 * 2) kmsg message is encoded as byte stream in buffer2
 * 3) QR-code image is generated in buffer1
 */

static uint panic_qr_version = CONFIG_DRM_PANIC_SCREEN_QR_VERSION;
module_param(panic_qr_version, uint, 0644);
MODULE_PARM_DESC(panic_qr_version, "maximum version (size) of the QR code");

#define MAX_QR_DATA 2956
#define MAX_ZLIB_RATIO 3
#define QR_BUFFER1_SIZE (MAX_ZLIB_RATIO * MAX_QR_DATA) /* Must also be > 4071  */
#define QR_BUFFER2_SIZE 4096
#define QR_MARGIN       4       /* 4 modules of foreground color around the qr code */

/* Compression parameters */
#define COMPR_LEVEL 6
#define WINDOW_BITS 12
#define MEM_LEVEL 4

static char *qrbuf1;
static char *qrbuf2;
static struct z_stream_s stream;

static void __init drm_panic_qr_init(void)
{
        qrbuf1 = kmalloc(QR_BUFFER1_SIZE, GFP_KERNEL);
        qrbuf2 = kmalloc(QR_BUFFER2_SIZE, GFP_KERNEL);
        stream.workspace = kmalloc(zlib_deflate_workspacesize(WINDOW_BITS, MEM_LEVEL),
                                   GFP_KERNEL);
}

static void drm_panic_qr_exit(void)
{
        kfree(qrbuf1);
        qrbuf1 = NULL;
        kfree(qrbuf2);
        qrbuf2 = NULL;
        kfree(stream.workspace);
        stream.workspace = NULL;
}

static int drm_panic_get_qr_code_url(u8 **qr_image)
{
        struct kmsg_dump_iter iter;
        char url[256];
        size_t kmsg_len, max_kmsg_size;
        char *kmsg;
        int max_qr_data_size, url_len;

        url_len = snprintf(url, sizeof(url), CONFIG_DRM_PANIC_SCREEN_QR_CODE_URL "?a=%s&v=%s&z=",
                           utsname()->machine, utsname()->release);

        max_qr_data_size = drm_panic_qr_max_data_size(panic_qr_version, url_len);
        max_kmsg_size = min(MAX_ZLIB_RATIO * max_qr_data_size, QR_BUFFER1_SIZE);

        /* get kmsg to buffer 1 */
        kmsg_dump_rewind(&iter);
        kmsg_dump_get_buffer(&iter, false, qrbuf1, max_kmsg_size, &kmsg_len);

        if (!kmsg_len)
                return -ENODATA;
        kmsg = qrbuf1;

try_again:
        if (zlib_deflateInit2(&stream, COMPR_LEVEL, Z_DEFLATED, WINDOW_BITS,
                              MEM_LEVEL, Z_DEFAULT_STRATEGY) != Z_OK)
                return -EINVAL;

        stream.next_in = kmsg;
        stream.avail_in = kmsg_len;
        stream.total_in = 0;
        stream.next_out = qrbuf2;
        stream.avail_out = QR_BUFFER2_SIZE;
        stream.total_out = 0;

        if (zlib_deflate(&stream, Z_FINISH) != Z_STREAM_END)
                return -EINVAL;

        if (zlib_deflateEnd(&stream) != Z_OK)
                return -EINVAL;

        if (stream.total_out > max_qr_data_size) {
                /* too much data for the QR code, so skip the first line and try again */
                kmsg = strchr(kmsg, '\n');
                if (!kmsg)
                        return -EINVAL;
                /* skip the first \n */
                kmsg += 1;
                kmsg_len = strlen(kmsg);
                goto try_again;
        }
        *qr_image = qrbuf2;

        /* generate qr code image in buffer2 */
        return drm_panic_qr_generate(url, qrbuf2, stream.total_out, QR_BUFFER2_SIZE,
                                     qrbuf1, QR_BUFFER1_SIZE);
}

static int drm_panic_get_qr_code_raw(u8 **qr_image)
{
        struct kmsg_dump_iter iter;
        size_t kmsg_len;
        size_t max_kmsg_size = min(drm_panic_qr_max_data_size(panic_qr_version, 0),
                                   QR_BUFFER1_SIZE);

        kmsg_dump_rewind(&iter);
        kmsg_dump_get_buffer(&iter, false, qrbuf1, max_kmsg_size, &kmsg_len);
        if (!kmsg_len)
                return -ENODATA;

        *qr_image = qrbuf1;
        return drm_panic_qr_generate(NULL, qrbuf1, kmsg_len, QR_BUFFER1_SIZE,
                                     qrbuf2, QR_BUFFER2_SIZE);
}

static int drm_panic_get_qr_code(u8 **qr_image)
{
        if (strlen(CONFIG_DRM_PANIC_SCREEN_QR_CODE_URL) > 0)
                return drm_panic_get_qr_code_url(qr_image);
        else
                return drm_panic_get_qr_code_raw(qr_image);
}

/*
 * Draw the panic message at the center of the screen, with a QR Code
 */
static int _draw_panic_static_qr_code(struct drm_scanout_buffer *sb)
{
        u32 fg_color = drm_draw_color_from_xrgb8888(CONFIG_DRM_PANIC_FOREGROUND_COLOR,
                                                    sb->format->format);
        u32 bg_color = drm_draw_color_from_xrgb8888(CONFIG_DRM_PANIC_BACKGROUND_COLOR,
                                                    sb->format->format);
        const struct font_desc *font = get_default_font(sb->width, sb->height, NULL, NULL);
        struct drm_rect r_screen, r_logo, r_msg, r_qr, r_qr_canvas;
        unsigned int max_qr_size, scale;
        unsigned int msg_width, msg_height;
        int qr_width, qr_canvas_width, qr_pitch, v_margin;
        u8 *qr_image;

        if (!font || !qrbuf1 || !qrbuf2 || !stream.workspace)
                return -ENOMEM;

        r_screen = DRM_RECT_INIT(0, 0, sb->width, sb->height);

        drm_panic_logo_rect(&r_logo, font);

        msg_width = min(get_max_line_len(panic_msg, panic_msg_lines) * font->width, sb->width);
        msg_height = min(panic_msg_lines * font->height, sb->height);
        r_msg = DRM_RECT_INIT(0, 0, msg_width, msg_height);

        max_qr_size = min(3 * sb->width / 4, 3 * sb->height / 4);

        qr_width = drm_panic_get_qr_code(&qr_image);
        if (qr_width <= 0)
                return -ENOSPC;

        qr_canvas_width = qr_width + QR_MARGIN * 2;
        scale = max_qr_size / qr_canvas_width;
        /* QR code is not readable if not scaled at least by 2 */
        if (scale < 2)
                return -ENOSPC;

        pr_debug("QR width %d and scale %d\n", qr_width, scale);
        r_qr_canvas = DRM_RECT_INIT(0, 0, qr_canvas_width * scale, qr_canvas_width * scale);

        v_margin = sb->height - drm_rect_height(&r_qr_canvas) - drm_rect_height(&r_msg);
        if (v_margin < 0)
                return -ENOSPC;
        v_margin /= 5;

        drm_rect_translate(&r_qr_canvas, (sb->width - r_qr_canvas.x2) / 2, 2 * v_margin);
        r_qr = DRM_RECT_INIT(r_qr_canvas.x1 + QR_MARGIN * scale, r_qr_canvas.y1 + QR_MARGIN * scale,
                             qr_width * scale, qr_width * scale);

        /* Center the panic message */
        drm_rect_translate(&r_msg, (sb->width - r_msg.x2) / 2,
                           3 * v_margin + drm_rect_height(&r_qr_canvas));

        /* Fill with the background color, and draw text on top */
        drm_panic_fill(sb, &r_screen, bg_color);

        if (!drm_rect_overlap(&r_logo, &r_msg) && !drm_rect_overlap(&r_logo, &r_qr_canvas))
                drm_panic_logo_draw(sb, &r_logo, font, fg_color);

        draw_txt_rectangle(sb, font, panic_msg, panic_msg_lines, true, &r_msg, fg_color);

        /* Draw the qr code */
        qr_pitch = DIV_ROUND_UP(qr_width, 8);
        drm_panic_fill(sb, &r_qr_canvas, fg_color);
        drm_panic_fill(sb, &r_qr, bg_color);
        drm_panic_blit(sb, &r_qr, qr_image, qr_pitch, scale, fg_color);
        return 0;
}

static void draw_panic_static_qr_code(struct drm_scanout_buffer *sb)
{
        if (_draw_panic_static_qr_code(sb))
                draw_panic_static_user(sb);
}
#else
static void draw_panic_static_qr_code(struct drm_scanout_buffer *sb)
{
        draw_panic_static_user(sb);
}

static void drm_panic_qr_init(void) {};
static void drm_panic_qr_exit(void) {};
#endif

/*
 * drm_panic_is_format_supported()
 * @format: a fourcc color code
 * Returns: true if supported, false otherwise.
 *
 * Check if drm_panic will be able to use this color format.
 */
static bool drm_panic_is_format_supported(const struct drm_format_info *format)
{
        if (format->num_planes != 1)
                return false;
        return drm_draw_color_from_xrgb8888(0xffffff, format->format) != 0;
}

static void draw_panic_dispatch(struct drm_scanout_buffer *sb)
{
        if (!strcmp(drm_panic_screen, "kmsg")) {
                draw_panic_static_kmsg(sb);
        } else if (!strcmp(drm_panic_screen, "qr_code")) {
                draw_panic_static_qr_code(sb);
        } else {
                draw_panic_static_user(sb);
        }
}

static void drm_panic_set_description(const char *description)
{
        u32 len;

        if (description) {
                struct drm_panic_line *desc_line = &panic_msg[panic_msg_lines - 1];

                desc_line->txt = description;
                len = strlen(description);
                /* ignore the last newline character */
                if (len && description[len - 1] == '\n')
                        len -= 1;
                desc_line->len = len;
        }
}

static void drm_panic_clear_description(void)
{
        struct drm_panic_line *desc_line = &panic_msg[panic_msg_lines - 1];

        desc_line->len = 0;
        desc_line->txt = NULL;
}

static void draw_panic_plane(struct drm_plane *plane, const char *description)
{
        struct drm_scanout_buffer sb = { };
        int ret;
        unsigned long flags;

        if (!drm_panic_trylock(plane->dev, flags))
                return;

        ret = plane->helper_private->get_scanout_buffer(plane, &sb);

        if (ret || !drm_panic_is_format_supported(sb.format))
                goto unlock;

        /* One of these should be set, or it can't draw pixels */
        if (!sb.set_pixel && !sb.pages && iosys_map_is_null(&sb.map[0]))
                goto unlock;

        drm_panic_set_description(description);

        draw_panic_dispatch(&sb);
        if (plane->helper_private->panic_flush)
                plane->helper_private->panic_flush(plane);

        drm_panic_clear_description();

unlock:
        drm_panic_unlock(plane->dev, flags);
}

static struct drm_plane *to_drm_plane(struct kmsg_dumper *kd)
{
        return container_of(kd, struct drm_plane, kmsg_panic);
}

static void drm_panic(struct kmsg_dumper *dumper, struct kmsg_dump_detail *detail)
{
        struct drm_plane *plane = to_drm_plane(dumper);

        if (detail->reason == KMSG_DUMP_PANIC)
                draw_panic_plane(plane, detail->description);
}


/*
 * DEBUG FS, This is currently unsafe.
 * Create one file per plane, so it's possible to debug one plane at a time.
 * TODO: It would be better to emulate an NMI context.
 */
#ifdef CONFIG_DRM_PANIC_DEBUG
#include <linux/debugfs.h>

static ssize_t debugfs_trigger_write(struct file *file, const char __user *user_buf,
                                     size_t count, loff_t *ppos)
{
        bool run;

        if (kstrtobool_from_user(user_buf, count, &run) == 0 && run) {
                struct drm_plane *plane = file->private_data;

                draw_panic_plane(plane, "Test from debugfs");
        }
        return count;
}

static const struct file_operations dbg_drm_panic_ops = {
        .owner = THIS_MODULE,
        .write = debugfs_trigger_write,
        .open = simple_open,
};

static void debugfs_register_plane(struct drm_plane *plane, int index)
{
        char fname[32];

        snprintf(fname, 32, "drm_panic_plane_%d", index);
        debugfs_create_file(fname, 0200, plane->dev->debugfs_root,
                            plane, &dbg_drm_panic_ops);
}
#else
static void debugfs_register_plane(struct drm_plane *plane, int index) {}
#endif /* CONFIG_DRM_PANIC_DEBUG */

/**
 * drm_panic_is_enabled
 * @dev: the drm device that may supports drm_panic
 *
 * returns true if the drm device supports drm_panic
 */
bool drm_panic_is_enabled(struct drm_device *dev)
{
        struct drm_plane *plane;

        if (!dev->mode_config.num_total_plane)
                return false;

        drm_for_each_plane(plane, dev)
                if (plane->helper_private && plane->helper_private->get_scanout_buffer)
                        return true;
        return false;
}
EXPORT_SYMBOL(drm_panic_is_enabled);

/**
 * drm_panic_register() - Initialize DRM panic for a device
 * @dev: the drm device on which the panic screen will be displayed.
 */
void drm_panic_register(struct drm_device *dev)
{
        struct drm_plane *plane;
        int registered_plane = 0;

        if (!dev->mode_config.num_total_plane)
                return;

        drm_for_each_plane(plane, dev) {
                if (!plane->helper_private || !plane->helper_private->get_scanout_buffer)
                        continue;
                plane->kmsg_panic.dump = drm_panic;
                plane->kmsg_panic.max_reason = KMSG_DUMP_PANIC;
                if (kmsg_dump_register(&plane->kmsg_panic))
                        drm_warn(dev, "Failed to register panic handler\n");
                else {
                        debugfs_register_plane(plane, registered_plane);
                        registered_plane++;
                }
        }
        if (registered_plane)
                drm_info(dev, "Registered %d planes with drm panic\n", registered_plane);
}

/**
 * drm_panic_unregister()
 * @dev: the drm device previously registered.
 */
void drm_panic_unregister(struct drm_device *dev)
{
        struct drm_plane *plane;

        if (!dev->mode_config.num_total_plane)
                return;

        drm_for_each_plane(plane, dev) {
                if (!plane->helper_private || !plane->helper_private->get_scanout_buffer)
                        continue;
                kmsg_dump_unregister(&plane->kmsg_panic);
        }
}

/**
 * drm_panic_init() - initialize DRM panic.
 */
void __init drm_panic_init(void)
{
        drm_panic_qr_init();
}

/**
 * drm_panic_exit() - Free the resources taken by drm_panic_exit()
 */
void drm_panic_exit(void)
{
        drm_panic_qr_exit();
}