The drivers/char/nvram module has previously only supported 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 suitable NVRAM. Signed-off-by: Finn Thain --- Changed since v1: - Don't bother acquiring the mutex for unimplemented ioctls. --- drivers/char/nvram.c | 71 ++++++++++++++++++++++++++++---------------------- include/linux/nvram.h | 2 + 2 files changed, 43 insertions(+), 30 deletions(-) Index: linux/drivers/char/nvram.c =================================================================== --- linux.orig/drivers/char/nvram.c 2015-08-23 20:40:59.000000000 +1000 +++ linux/drivers/char/nvram.c 2015-08-23 20:41:02.000000000 +1000 @@ -153,16 +153,25 @@ static void __nvram_set_checksum(void) __nvram_write_byte(sum & 0xff, PC_CKS_LOC + 1); } -#if 0 -void nvram_set_checksum(void) +static long nvram_set_checksum(void) { - unsigned long flags; + spin_lock_irq(&rtc_lock); + __nvram_set_checksum(); + spin_unlock_irq(&rtc_lock); + return 0; +} + +static long nvram_initialize(void) +{ + ssize_t i; - spin_lock_irqsave(&rtc_lock, flags); + 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 nvram_get_size(void) { @@ -173,6 +182,8 @@ const struct nvram_ops arch_nvram_ops = .read_byte = nvram_read_byte, .write_byte = nvram_write_byte, .get_size = nvram_get_size, + .set_checksum = nvram_set_checksum, + .initialize = nvram_initialize, }; EXPORT_SYMBOL(arch_nvram_ops); @@ -272,51 +283,51 @@ checksum_err: 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; } Index: linux/include/linux/nvram.h =================================================================== --- linux.orig/include/linux/nvram.h 2015-08-23 20:40:59.000000000 +1000 +++ linux/include/linux/nvram.h 2015-08-23 20:41:02.000000000 +1000 @@ -17,6 +17,8 @@ struct nvram_ops { unsigned char (*read_byte)(int); void (*write_byte)(unsigned char, int); ssize_t (*get_size)(void); + long (*set_checksum)(void); + long (*initialize)(void); }; extern const struct nvram_ops arch_nvram_ops;