+/*
+ * All these chips have at least 64 bytes of address space, shared by
+ * RTC registers and NVRAM. Most of those bytes of NVRAM are used
+ * by boot firmware. Modern chips have 128 or 256 bytes.
+ */
+
+#define NVRAM_OFFSET (RTC_REG_D + 1)
+
+static ssize_t
+cmos_nvram_read(struct kobject *kobj, struct bin_attribute *attr,
+ char *buf, loff_t off, size_t count)
+{
+ int retval;
+
+ if (unlikely(off >= attr->size))
+ return 0;
+ if (unlikely(off < 0))
+ return -EINVAL;
+ if ((off + count) > attr->size)
+ count = attr->size - off;
+
+ off += NVRAM_OFFSET;
+ spin_lock_irq(&rtc_lock);
+ for (retval = 0; count; count--, off++, retval++) {
+ if (off < 128)
+ *buf++ = CMOS_READ(off);
+ else if (can_bank2)
+ *buf++ = cmos_read_bank2(off);
+ else
+ break;
+ }
+ spin_unlock_irq(&rtc_lock);
+
+ return retval;
+}
+
+static ssize_t
+cmos_nvram_write(struct kobject *kobj, struct bin_attribute *attr,
+ char *buf, loff_t off, size_t count)
+{
+ struct cmos_rtc *cmos;
+ int retval;
+
+ cmos = dev_get_drvdata(container_of(kobj, struct device, kobj));
+ if (unlikely(off >= attr->size))
+ return -EFBIG;
+ if (unlikely(off < 0))
+ return -EINVAL;
+ if ((off + count) > attr->size)
+ count = attr->size - off;
+
+ /* NOTE: on at least PCs and Ataris, the boot firmware uses a
+ * checksum on part of the NVRAM data. That's currently ignored
+ * here. If userspace is smart enough to know what fields of
+ * NVRAM to update, updating checksums is also part of its job.
+ */
+ off += NVRAM_OFFSET;
+ spin_lock_irq(&rtc_lock);
+ for (retval = 0; count; count--, off++, retval++) {
+ /* don't trash RTC registers */
+ if (off == cmos->day_alrm
+ || off == cmos->mon_alrm
+ || off == cmos->century)
+ buf++;
+ else if (off < 128)
+ CMOS_WRITE(*buf++, off);
+ else if (can_bank2)
+ cmos_write_bank2(*buf++, off);
+ else
+ break;
+ }
+ spin_unlock_irq(&rtc_lock);
+
+ return retval;
+}
+
+static struct bin_attribute nvram = {
+ .attr = {
+ .name = "nvram",
+ .mode = S_IRUGO | S_IWUSR,
+ },
+
+ .read = cmos_nvram_read,
+ .write = cmos_nvram_write,
+ /* size gets set up later */
+};
+
+/*----------------------------------------------------------------*/
+