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Subject[PATCH v9 08/22] char/nvram: Allow the set_checksum and initialize ioctls to be omitted
Date
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>
---
Changed since v8:
- Renamed nvram_* functions to avoid name collisions.
---
drivers/char/nvram.c | 70 ++++++++++++++++++++++++-------------------
include/linux/nvram.h | 2 ++
2 files changed, 42 insertions(+), 30 deletions(-)

diff --git a/drivers/char/nvram.c b/drivers/char/nvram.c
index 2df391f78986..f88ef41d0598 100644
--- a/drivers/char/nvram.c
+++ b/drivers/char/nvram.c
@@ -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_irq(&rtc_lock);
+ __nvram_set_checksum();
+ spin_unlock_irq(&rtc_lock);
+ return 0;
+}

- spin_lock_irqsave(&rtc_lock, flags);
+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_irqrestore(&rtc_lock, flags);
+ 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;
}
diff --git a/include/linux/nvram.h b/include/linux/nvram.h
index bb4ea8cc6ea6..31c763087746 100644
--- a/include/linux/nvram.h
+++ b/include/linux/nvram.h
@@ -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;
--
2.19.2
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