1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_NVRAM_H
3#define _LINUX_NVRAM_H
4
5#include <linux/errno.h>
6#include <uapi/linux/nvram.h>
7
8#ifdef CONFIG_PPC
9#include <asm/machdep.h>
10#endif
11
12/**
13 * struct nvram_ops - NVRAM functionality made available to drivers
14 * @read: validate checksum (if any) then load a range of bytes from NVRAM
15 * @write: store a range of bytes to NVRAM then update checksum (if any)
16 * @read_byte: load a single byte from NVRAM
17 * @write_byte: store a single byte to NVRAM
18 * @get_size: return the fixed number of bytes in the NVRAM
19 *
20 * Architectures which provide an nvram ops struct need not implement all
21 * of these methods. If the NVRAM hardware can be accessed only one byte
22 * at a time then it may be sufficient to provide .read_byte and .write_byte.
23 * If the NVRAM has a checksum (and it is to be checked) the .read and
24 * .write methods can be used to implement that efficiently.
25 *
26 * Portable drivers may use the wrapper functions defined here.
27 * The nvram_read() and nvram_write() functions call the .read and .write
28 * methods when available and fall back on the .read_byte and .write_byte
29 * methods otherwise.
30 */
31
32struct nvram_ops {
33 ssize_t (*get_size)(void);
34 unsigned char (*read_byte)(int);
35 void (*write_byte)(unsigned char, int);
36 ssize_t (*read)(char *, size_t, loff_t *);
37 ssize_t (*write)(char *, size_t, loff_t *);
38#if defined(CONFIG_X86) || defined(CONFIG_M68K)
39 long (*initialize)(void);
40 long (*set_checksum)(void);
41#endif
42};
43
44extern const struct nvram_ops arch_nvram_ops;
45
46static inline ssize_t nvram_get_size(void)
47{
48#ifdef CONFIG_PPC
49 if (ppc_md.nvram_size)
50 return ppc_md.nvram_size();
51#else
52 if (arch_nvram_ops.get_size)
53 return arch_nvram_ops.get_size();
54#endif
55 return -ENODEV;
56}
57
58static inline unsigned char nvram_read_byte(int addr)
59{
60#ifdef CONFIG_PPC
61 if (ppc_md.nvram_read_val)
62 return ppc_md.nvram_read_val(addr);
63#else
64 if (arch_nvram_ops.read_byte)
65 return arch_nvram_ops.read_byte(addr);
66#endif
67 return 0xFF;
68}
69
70static inline void nvram_write_byte(unsigned char val, int addr)
71{
72#ifdef CONFIG_PPC
73 if (ppc_md.nvram_write_val)
74 ppc_md.nvram_write_val(addr, val);
75#else
76 if (arch_nvram_ops.write_byte)
77 arch_nvram_ops.write_byte(val, addr);
78#endif
79}
80
81static inline ssize_t nvram_read_bytes(char *buf, size_t count, loff_t *ppos)
82{
83 ssize_t nvram_size = nvram_get_size();
84 loff_t i;
85 char *p = buf;
86
87 if (nvram_size < 0)
88 return nvram_size;
89 for (i = *ppos; count > 0 && i < nvram_size; ++i, ++p, --count)
90 *p = nvram_read_byte(addr: i);
91 *ppos = i;
92 return p - buf;
93}
94
95static inline ssize_t nvram_write_bytes(char *buf, size_t count, loff_t *ppos)
96{
97 ssize_t nvram_size = nvram_get_size();
98 loff_t i;
99 char *p = buf;
100
101 if (nvram_size < 0)
102 return nvram_size;
103 for (i = *ppos; count > 0 && i < nvram_size; ++i, ++p, --count)
104 nvram_write_byte(val: *p, addr: i);
105 *ppos = i;
106 return p - buf;
107}
108
109static inline ssize_t nvram_read(char *buf, size_t count, loff_t *ppos)
110{
111#ifdef CONFIG_PPC
112 if (ppc_md.nvram_read)
113 return ppc_md.nvram_read(buf, count, ppos);
114#else
115 if (arch_nvram_ops.read)
116 return arch_nvram_ops.read(buf, count, ppos);
117#endif
118 return nvram_read_bytes(buf, count, ppos);
119}
120
121static inline ssize_t nvram_write(char *buf, size_t count, loff_t *ppos)
122{
123#ifdef CONFIG_PPC
124 if (ppc_md.nvram_write)
125 return ppc_md.nvram_write(buf, count, ppos);
126#else
127 if (arch_nvram_ops.write)
128 return arch_nvram_ops.write(buf, count, ppos);
129#endif
130 return nvram_write_bytes(buf, count, ppos);
131}
132
133#endif /* _LINUX_NVRAM_H */
134