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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_NVRAM_H
#define _LINUX_NVRAM_H
#include <linux/errno.h>
#include <uapi/linux/nvram.h>
/**
* struct nvram_ops - NVRAM functionality made available to drivers
* @read: validate checksum (if any) then load a range of bytes from NVRAM
* @write: store a range of bytes to NVRAM then update checksum (if any)
* @read_byte: load a single byte from NVRAM
* @write_byte: store a single byte to NVRAM
* @get_size: return the fixed number of bytes in the NVRAM
*
* Architectures which provide an nvram ops struct need not implement all
* of these methods. If the NVRAM hardware can be accessed only one byte
* at a time then it may be sufficient to provide .read_byte and .write_byte.
* If the NVRAM has a checksum (and it is to be checked) the .read and
* .write methods can be used to implement that efficiently.
*
* Portable drivers may use the wrapper functions defined here.
* The nvram_read() and nvram_write() functions call the .read and .write
* methods when available and fall back on the .read_byte and .write_byte
* methods otherwise.
*/
struct nvram_ops {
ssize_t (*get_size)(void);
unsigned char (*read_byte)(int);
void (*write_byte)(unsigned char, int);
ssize_t (*read)(char *, size_t, loff_t *);
ssize_t (*write)(char *, size_t, loff_t *);
#if defined(CONFIG_X86) || defined(CONFIG_M68K)
long (*initialize)(void);
long (*set_checksum)(void);
#endif
};
extern const struct nvram_ops arch_nvram_ops;
static inline ssize_t nvram_get_size(void)
{
#ifdef CONFIG_PPC
#else
if (arch_nvram_ops.get_size)
return arch_nvram_ops.get_size();
#endif
return -ENODEV;
}
static inline unsigned char nvram_read_byte(int addr)
{
#ifdef CONFIG_PPC
#else
if (arch_nvram_ops.read_byte)
return arch_nvram_ops.read_byte(addr);
#endif
return 0xFF;
}
static inline void nvram_write_byte(unsigned char val, int addr)
{
#ifdef CONFIG_PPC
#else
if (arch_nvram_ops.write_byte)
arch_nvram_ops.write_byte(val, addr);
#endif
}
static inline ssize_t nvram_read_bytes(char *buf, size_t count, loff_t *ppos)
{
ssize_t nvram_size = nvram_get_size();
loff_t i;
char *p = buf;
if (nvram_size < 0)
return nvram_size;
for (i = *ppos; count > 0 && i < nvram_size; ++i, ++p, --count)
*p = nvram_read_byte(i);
*ppos = i;
return p - buf;
}
static inline ssize_t nvram_write_bytes(char *buf, size_t count, loff_t *ppos)
{
ssize_t nvram_size = nvram_get_size();
loff_t i;
char *p = buf;
if (nvram_size < 0)
return nvram_size;
for (i = *ppos; count > 0 && i < nvram_size; ++i, ++p, --count)
nvram_write_byte(*p, i);
*ppos = i;
return p - buf;
}
static inline ssize_t nvram_read(char *buf, size_t count, loff_t *ppos)
{
if (arch_nvram_ops.read)
return arch_nvram_ops.read(buf, count, ppos);
return nvram_read_bytes(buf, count, ppos);
}
static inline ssize_t nvram_write(char *buf, size_t count, loff_t *ppos)
{
if (arch_nvram_ops.write)
return arch_nvram_ops.write(buf, count, ppos);
return nvram_write_bytes(buf, count, ppos);
}
#endif /* _LINUX_NVRAM_H */
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