1/* SPDX-License-Identifier: GPL-2.0 or MIT */
2
3/*
4 * Copyright (c) 2024 Intel
5 * Copyright (c) 2024 Red Hat
6 */
7
8#ifndef __DRM_PANIC_H__
9#define __DRM_PANIC_H__
10
11#include <linux/module.h>
12#include <linux/types.h>
13#include <linux/iosys-map.h>
14
15#include <drm/drm_device.h>
16#include <drm/drm_fourcc.h>
17
18/**
19 * struct drm_scanout_buffer - DRM scanout buffer
20 *
21 * This structure holds the information necessary for drm_panic to draw the
22 * panic screen, and display it.
23 */
24struct drm_scanout_buffer {
25 /**
26 * @format:
27 *
28 * drm format of the scanout buffer.
29 */
30 const struct drm_format_info *format;
31
32 /**
33 * @map:
34 *
35 * Virtual address of the scanout buffer, either in memory or iomem.
36 * The scanout buffer should be in linear format, and can be directly
37 * sent to the display hardware. Tearing is not an issue for the panic
38 * screen.
39 */
40 struct iosys_map map[DRM_FORMAT_MAX_PLANES];
41
42 /**
43 * @pages: Optional, if the scanout buffer is not mapped, set this field
44 * to the array of pages of the scanout buffer. The panic code will use
45 * kmap_local_page_try_from_panic() to map one page at a time to write
46 * all the pixels. This array shouldn't be allocated from the
47 * get_scanoutbuffer() callback.
48 * The scanout buffer should be in linear format.
49 */
50 struct page **pages;
51
52 /**
53 * @width: Width of the scanout buffer, in pixels.
54 */
55 unsigned int width;
56
57 /**
58 * @height: Height of the scanout buffer, in pixels.
59 */
60 unsigned int height;
61
62 /**
63 * @pitch: Length in bytes between the start of two consecutive lines.
64 */
65 unsigned int pitch[DRM_FORMAT_MAX_PLANES];
66
67 /**
68 * @set_pixel: Optional function, to set a pixel color on the
69 * framebuffer. It allows to handle special tiling format inside the
70 * driver. It takes precedence over the @map and @pages fields.
71 */
72 void (*set_pixel)(struct drm_scanout_buffer *sb, unsigned int x,
73 unsigned int y, u32 color);
74
75 /**
76 * @private: private pointer that you can use in the callbacks
77 * set_pixel()
78 */
79 void *private;
80
81};
82
83#ifdef CONFIG_DRM_PANIC
84
85/**
86 * drm_panic_trylock - try to enter the panic printing critical section
87 * @dev: struct drm_device
88 * @flags: unsigned long irq flags you need to pass to the unlock() counterpart
89 *
90 * This function must be called by any panic printing code. The panic printing
91 * attempt must be aborted if the trylock fails.
92 *
93 * Panic printing code can make the following assumptions while holding the
94 * panic lock:
95 *
96 * - Anything protected by drm_panic_lock() and drm_panic_unlock() pairs is safe
97 * to access.
98 *
99 * - Furthermore the panic printing code only registers in drm_dev_unregister()
100 * and gets removed in drm_dev_unregister(). This allows the panic code to
101 * safely access any state which is invariant in between these two function
102 * calls, like the list of planes &drm_mode_config.plane_list or most of the
103 * struct drm_plane structure.
104 *
105 * Specifically thanks to the protection around plane updates in
106 * drm_atomic_helper_swap_state() the following additional guarantees hold:
107 *
108 * - It is safe to deference the drm_plane.state pointer.
109 *
110 * - Anything in struct drm_plane_state or the driver's subclass thereof which
111 * stays invariant after the atomic check code has finished is safe to access.
112 * Specifically this includes the reference counted pointers to framebuffer
113 * and buffer objects.
114 *
115 * - Anything set up by &drm_plane_helper_funcs.fb_prepare and cleaned up
116 * &drm_plane_helper_funcs.fb_cleanup is safe to access, as long as it stays
117 * invariant between these two calls. This also means that for drivers using
118 * dynamic buffer management the framebuffer is pinned, and therefer all
119 * relevant datastructures can be accessed without taking any further locks
120 * (which would be impossible in panic context anyway).
121 *
122 * - Importantly, software and hardware state set up by
123 * &drm_plane_helper_funcs.begin_fb_access and
124 * &drm_plane_helper_funcs.end_fb_access is not safe to access.
125 *
126 * Drivers must not make any assumptions about the actual state of the hardware,
127 * unless they explicitly protected these hardware access with drm_panic_lock()
128 * and drm_panic_unlock().
129 *
130 * Return:
131 * %0 when failing to acquire the raw spinlock, nonzero on success.
132 */
133#define drm_panic_trylock(dev, flags) \
134 raw_spin_trylock_irqsave(&(dev)->mode_config.panic_lock, flags)
135
136/**
137 * drm_panic_lock - protect panic printing relevant state
138 * @dev: struct drm_device
139 * @flags: unsigned long irq flags you need to pass to the unlock() counterpart
140 *
141 * This function must be called to protect software and hardware state that the
142 * panic printing code must be able to rely on. The protected sections must be
143 * as small as possible. It uses the irqsave/irqrestore variant, and can be
144 * called from irq handler. Examples include:
145 *
146 * - Access to peek/poke or other similar registers, if that is the way the
147 * driver prints the pixels into the scanout buffer at panic time.
148 *
149 * - Updates to pointers like &drm_plane.state, allowing the panic handler to
150 * safely deference these. This is done in drm_atomic_helper_swap_state().
151 *
152 * - An state that isn't invariant and that the driver must be able to access
153 * during panic printing.
154 */
155
156#define drm_panic_lock(dev, flags) \
157 raw_spin_lock_irqsave(&(dev)->mode_config.panic_lock, flags)
158
159/**
160 * drm_panic_unlock - end of the panic printing critical section
161 * @dev: struct drm_device
162 * @flags: irq flags that were returned when acquiring the lock
163 *
164 * Unlocks the raw spinlock acquired by either drm_panic_lock() or
165 * drm_panic_trylock().
166 */
167#define drm_panic_unlock(dev, flags) \
168 raw_spin_unlock_irqrestore(&(dev)->mode_config.panic_lock, flags)
169
170#else
171
172static inline bool drm_panic_trylock(struct drm_device *dev, unsigned long flags)
173{
174 return true;
175}
176
177static inline void drm_panic_lock(struct drm_device *dev, unsigned long flags) {}
178static inline void drm_panic_unlock(struct drm_device *dev, unsigned long flags) {}
179
180#endif
181
182#if defined(CONFIG_DRM_PANIC_SCREEN_QR_CODE)
183size_t drm_panic_qr_max_data_size(u8 version, size_t url_len);
184
185u8 drm_panic_qr_generate(const char *url, u8 *data, size_t data_len, size_t data_size,
186 u8 *tmp, size_t tmp_size);
187#endif
188
189#endif /* __DRM_PANIC_H__ */
190

source code of linux/include/drm/drm_panic.h