powerpc/nvram: Allow byte length reads from mmio NVRAM driver

Add a byte length read and write interface compatible with the
nvram_generic driver interface to the mmio driver.
Signed-off-by: Martyn Welch <martyn.welch@gefanuc.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/sysdev/mmio_nvram.c

@@ -53,6 +53,23 @@ static ssize_t mmio_nvram_read(char *buf, size_t count, loff_t *index)
 	return count;
 }
 
+static unsigned char mmio_nvram_read_val(int addr)
+{
+	unsigned long flags;
+	unsigned char val;
+
+	if (addr >= mmio_nvram_len)
+		return 0xff;
+
+	spin_lock_irqsave(&mmio_nvram_lock, flags);
+
+	val = ioread8(mmio_nvram_start + addr);
+
+	spin_unlock_irqrestore(&mmio_nvram_lock, flags);
+
+	return val;
+}
+
 static ssize_t mmio_nvram_write(char *buf, size_t count, loff_t *index)
 {
 	unsigned long flags;
@@ -72,6 +89,19 @@ static ssize_t mmio_nvram_write(char *buf, size_t count, loff_t *index)
 	return count;
 }
 
+void mmio_nvram_write_val(int addr, unsigned char val)
+{
+	unsigned long flags;
+
+	if (addr < mmio_nvram_len) {
+		spin_lock_irqsave(&mmio_nvram_lock, flags);
+
+		iowrite8(val, mmio_nvram_start + addr);
+
+		spin_unlock_irqrestore(&mmio_nvram_lock, flags);
+	}
+}
+
 static ssize_t mmio_nvram_get_size(void)
 {
 	return mmio_nvram_len;
@@ -114,6 +144,8 @@ int __init mmio_nvram_init(void)
 	printk(KERN_INFO "mmio NVRAM, %luk at 0x%lx mapped to %p\n",
 	       mmio_nvram_len >> 10, nvram_addr, mmio_nvram_start);
 
+	ppc_md.nvram_read_val	= mmio_nvram_read_val;
+	ppc_md.nvram_write_val	= mmio_nvram_write_val;
 	ppc_md.nvram_read	= mmio_nvram_read;
 	ppc_md.nvram_write	= mmio_nvram_write;
 	ppc_md.nvram_size	= mmio_nvram_get_size;