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char/nvram: Allow the set_checksum and initialize ioctls to be omitted

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The drivers/char/nvram.c module has previously supported only RTC "CMOS"
NVRAM, for which it provides appropriate checksum ioctls. Make these
ioctls optional so the module can be re-used with other kinds of NVRAM.

The ops struct methods that implement the ioctls now return error
codes so that a multi-platform kernel binary can do the right thing when
running on hardware without a suitable NVRAM.

Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Finn Thain 2019-01-15 15:18:56 +11:00 committed by Greg Kroah-Hartman
parent d5bbb5021c
commit 2d58636e0a
2 changed files with 43 additions and 31 deletions
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72
drivers/char/nvram.c
View file

@ -136,16 +136,25 @@ static void __nvram_set_checksum(void)
__nvram_write_byte(sum & 0xff, PC_CKS_LOC + 1);
}
#if 0
void nvram_set_checksum(void)
static long pc_nvram_set_checksum(void)
{
unsigned long flags;
spin_lock_irqsave(&rtc_lock, flags);
spin_lock_irq(&rtc_lock);
__nvram_set_checksum();
spin_unlock_irqrestore(&rtc_lock, flags);
spin_unlock_irq(&rtc_lock);
return 0;
}
static long pc_nvram_initialize(void)
{
ssize_t i;
spin_lock_irq(&rtc_lock);
for (i = 0; i < NVRAM_BYTES; ++i)
__nvram_write_byte(0, i);
__nvram_set_checksum();
spin_unlock_irq(&rtc_lock);
return 0;
}
#endif /* 0 */
static ssize_t pc_nvram_get_size(void)
{
@ -156,6 +165,8 @@ const struct nvram_ops arch_nvram_ops = {
.read_byte = pc_nvram_read_byte,
.write_byte = pc_nvram_write_byte,
.get_size = pc_nvram_get_size,
.set_checksum = pc_nvram_set_checksum,
.initialize = pc_nvram_initialize,
};
EXPORT_SYMBOL(arch_nvram_ops);
#endif /* CONFIG_X86 */
@ -241,51 +252,50 @@ static ssize_t nvram_misc_write(struct file *file, const char __user *buf,
static long nvram_misc_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
{
int i;
long ret = -ENOTTY;
switch (cmd) {
case NVRAM_INIT:
/* initialize NVRAM contents and checksum */
if (!capable(CAP_SYS_ADMIN))
return -EACCES;
mutex_lock(&nvram_mutex);
spin_lock_irq(&rtc_lock);
for (i = 0; i < NVRAM_BYTES; ++i)
__nvram_write_byte(0, i);
__nvram_set_checksum();
spin_unlock_irq(&rtc_lock);
mutex_unlock(&nvram_mutex);
return 0;
if (arch_nvram_ops.initialize != NULL) {
mutex_lock(&nvram_mutex);
ret = arch_nvram_ops.initialize();
mutex_unlock(&nvram_mutex);
}
break;
case NVRAM_SETCKS:
/* just set checksum, contents unchanged (maybe useful after
* checksum garbaged somehow...) */
if (!capable(CAP_SYS_ADMIN))
return -EACCES;
mutex_lock(&nvram_mutex);
spin_lock_irq(&rtc_lock);
__nvram_set_checksum();
spin_unlock_irq(&rtc_lock);
mutex_unlock(&nvram_mutex);
return 0;
default:
return -ENOTTY;
if (arch_nvram_ops.set_checksum != NULL) {
mutex_lock(&nvram_mutex);
ret = arch_nvram_ops.set_checksum();
mutex_unlock(&nvram_mutex);
}
break;
}
return ret;
}
static int nvram_misc_open(struct inode *inode, struct file *file)
{
spin_lock(&nvram_state_lock);
/* Prevent multiple readers/writers if desired. */
if ((nvram_open_cnt && (file->f_flags & O_EXCL)) ||
(nvram_open_mode & NVRAM_EXCL) ||
((file->f_mode & FMODE_WRITE) && (nvram_open_mode & NVRAM_WRITE))) {
(nvram_open_mode & NVRAM_EXCL)) {
spin_unlock(&nvram_state_lock);
return -EBUSY;
}
/* Prevent multiple writers if the set_checksum ioctl is implemented. */
if ((arch_nvram_ops.set_checksum != NULL) &&
(file->f_mode & FMODE_WRITE) && (nvram_open_mode & NVRAM_WRITE)) {
spin_unlock(&nvram_state_lock);
return -EBUSY;
}

2
include/linux/nvram.h
View file

@ -31,6 +31,8 @@ struct nvram_ops {
void (*write_byte)(unsigned char, int);
ssize_t (*read)(char *, size_t, loff_t *);
ssize_t (*write)(char *, size_t, loff_t *);
long (*initialize)(void);
long (*set_checksum)(void);
};
extern const struct nvram_ops arch_nvram_ops;