include/linux/nvram.h

   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
  32 struct 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
  44 extern const struct nvram_ops arch_nvram_ops;
  45
  46 static 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
  58 static 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
  70 static 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
  81 static 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(i);
  91         *ppos = i;
  92         return p - buf;
  93 }
  94
  95 static 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(*p, i);
 105         *ppos = i;
 106         return p - buf;
 107 }
 108
 109 static 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
 121 static 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 */