On Sat, 29 Dec 2018, Arnd Bergmann wrote:

quoted

--- a/drivers/char/nvram.c
+++ b/drivers/char/nvram.c

@@ -48,6 +48,10 @@
 #include <linux/mutex.h>
 #include <linux/pagemap.h>

+#ifdef CONFIG_PPC
+#include <asm/nvram.h>
+#include <asm/machdep.h>
+#endif

 static DEFINE_MUTEX(nvram_mutex);
 static DEFINE_SPINLOCK(nvram_state_lock);

@@ -331,6 +335,37 @@ static long nvram_misc_ioctl(struct file *file, unsigned int cmd,
        long ret = -ENOTTY;

        switch (cmd) {
+#ifdef CONFIG_PPC
+       case OBSOLETE_PMAC_NVRAM_GET_OFFSET:
+               pr_warn("nvram: Using obsolete PMAC_NVRAM_GET_OFFSET ioctl\n");
+               /* fall through */
+       case IOC_NVRAM_GET_OFFSET:
+               ret = -EINVAL;
+#ifdef CONFIG_PPC_PMAC

I think it would make be nicer here to keep the ppc bits in arch/ppc,
and instead add a .ioctl() callback to nvram_ops.

The problem with having an nvram_ops.ioctl() method is the code in the 
!PPC branch. That code would get duplicated because it's needed by both 
X86 and M68K, to implement the checksum ioctls.

quoted

@@ -369,12 +405,14 @@ static int nvram_misc_open(struct inode *inode, struct file *file)
                return -EBUSY;
        }

+#ifndef CONFIG_PPC
        /* 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;
        }
+#endif

diff --git a/include/linux/nvram.h b/include/linux/nvram.h
index b7bfaec60a43..24a57675dba1 100644
--- a/include/linux/nvram.h
+++ b/include/linux/nvram.h

@@ -18,8 +18,12 @@ struct nvram_ops {
        unsigned char   (*read_byte)(int);
        void            (*write_byte)(unsigned char, int);
        ssize_t         (*get_size)(void);
+#ifdef CONFIG_PPC
+       long            (*sync)(void);
+#else
        long            (*set_checksum)(void);
        long            (*initialize)(void);
+#endif
 };

Maybe just leave all entries visible here, and avoid the above #ifdef checks.

The #ifdef isn't there just to save a few bytes, though it does do that. 
It's really meant to cause a build failure when I mess up somewhere. But 
I'm happy to change it if you can see a reason to do so (?)

-- 

       Arnd