m68k/atari: Implement arch_nvram_ops struct

By implementing an arch_nvram_ops struct, a platform can re-use the
drivers/char/nvram.c module without needing any arch-specific code
in that module. Atari does so here.
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

arch/m68k/atari/nvram.c

@@ -74,6 +74,55 @@ static void __nvram_set_checksum(void)
 	__nvram_write_byte(sum, ATARI_CKS_LOC + 1);
 }
 
+static ssize_t atari_nvram_read(char *buf, size_t count, loff_t *ppos)
+{
+	char *p = buf;
+	loff_t i;
+
+	spin_lock_irq(&rtc_lock);
+	if (!__nvram_check_checksum()) {
+		spin_unlock_irq(&rtc_lock);
+		return -EIO;
+	}
+	for (i = *ppos; count > 0 && i < NVRAM_BYTES; --count, ++i, ++p)
+		*p = __nvram_read_byte(i);
+	spin_unlock_irq(&rtc_lock);
+
+	*ppos = i;
+	return p - buf;
+}
+
+static ssize_t atari_nvram_write(char *buf, size_t count, loff_t *ppos)
+{
+	char *p = buf;
+	loff_t i;
+
+	spin_lock_irq(&rtc_lock);
+	if (!__nvram_check_checksum()) {
+		spin_unlock_irq(&rtc_lock);
+		return -EIO;
+	}
+	for (i = *ppos; count > 0 && i < NVRAM_BYTES; --count, ++i, ++p)
+		__nvram_write_byte(*p, i);
+	__nvram_set_checksum();
+	spin_unlock_irq(&rtc_lock);
+
+	*ppos = i;
+	return p - buf;
+}
+
+static ssize_t atari_nvram_get_size(void)
+{
+	return NVRAM_BYTES;
+}
+
+const struct nvram_ops arch_nvram_ops = {
+	.read           = atari_nvram_read,
+	.write          = atari_nvram_write,
+	.get_size       = atari_nvram_get_size,
+};
+EXPORT_SYMBOL(arch_nvram_ops);
+
 #ifdef CONFIG_PROC_FS
 static struct {
 	unsigned char val;

include/linux/nvram.h

@@ -5,8 +5,18 @@
 #include <linux/errno.h>
 #include <uapi/linux/nvram.h>
 
+struct nvram_ops {
+	ssize_t         (*get_size)(void);
+	ssize_t         (*read)(char *, size_t, loff_t *);
+	ssize_t         (*write)(char *, size_t, loff_t *);
+};
+
+extern const struct nvram_ops arch_nvram_ops;
+
 static inline ssize_t nvram_get_size(void)
 {
+	if (arch_nvram_ops.get_size)
+		return arch_nvram_ops.get_size();
 	return -ENODEV;
 }
 
@@ -21,11 +31,15 @@ static inline void nvram_write_byte(unsigned char val, int addr)
 
 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 -ENODEV;
 }
 
 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 -ENODEV;
 }