1 files changed, 117 insertions, 12 deletions

diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index 29cf1457ca10..ab455ddb16cf 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -393,6 +393,80 @@ static const struct rtc_class_ops cmos_rtc_ops = {
 
 /*----------------------------------------------------------------*/
 
+/*
+ * 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 ((off + count) > attr->size)
+                count = attr->size - off;
+
+        spin_lock_irq(&rtc_lock);
+        for (retval = 0, off += NVRAM_OFFSET; count--; retval++, off++)
+                *buf++ = CMOS_READ(off);
+        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 ((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.
+         */
+        spin_lock_irq(&rtc_lock);
+        for (retval = 0, off += NVRAM_OFFSET; count--; retval++, off++) {
+                /* don't trash RTC registers */
+                if (off == cmos->day_alrm
+                                || off == cmos->mon_alrm
+                                || off == cmos->century)
+                        buf++;
+                else
+                        CMOS_WRITE(*buf++, off);
+        }
+        spin_unlock_irq(&rtc_lock);
+
+        return retval;
+}
+
+static struct bin_attribute nvram = {
+        .attr = {
+                .name   = "nvram",
+                .mode   = S_IRUGO | S_IWUSR,
+                .owner  = THIS_MODULE,
+        },
+
+        .read   = cmos_nvram_read,
+        .write  = cmos_nvram_write,
+        /* size gets set up later */
+};
+
+/*----------------------------------------------------------------*/
+
 static struct cmos_rtc  cmos_rtc;
 
 static irqreturn_t cmos_interrupt(int irq, void *p)
@@ -412,11 +486,9 @@ static irqreturn_t cmos_interrupt(int irq, void *p)
 }
 
 #ifdef  CONFIG_PNP
-#define is_pnp()        1
 #define INITSECTION
 
 #else
-#define is_pnp()        0
 #define INITSECTION     __init
 #endif
 
@@ -426,6 +498,7 @@ cmos_do_probe(struct device *dev, struct resource *ports, int rtc_irq)
         struct cmos_rtc_board_info      *info = dev->platform_data;
         int                             retval = 0;
         unsigned char                   rtc_control;
+        unsigned                        address_space;
 
         /* there can be only one ... */
         if (cmos_rtc.dev)
@@ -450,15 +523,36 @@ cmos_do_probe(struct device *dev, struct resource *ports, int rtc_irq)
         cmos_rtc.irq = rtc_irq;
         cmos_rtc.iomem = ports;
 
+        /* Heuristic to deduce NVRAM size ... do what the legacy NVRAM
+         * driver did, but don't reject unknown configs.   Old hardware
+         * won't address 128 bytes, and for now we ignore the way newer
+         * chips can address 256 bytes (using two more i/o ports).
+         */
+#if     defined(CONFIG_ATARI)
+        address_space = 64;
+#elif defined(__i386__) || defined(__x86_64__) || defined(__arm__)
+        address_space = 128;
+#else
+#warning Assuming 128 bytes of RTC+NVRAM address space, not 64 bytes.
+        address_space = 128;
+#endif
+
         /* For ACPI systems extension info comes from the FADT.  On others,
          * board specific setup provides it as appropriate.  Systems where
          * the alarm IRQ isn't automatically a wakeup IRQ (like ACPI, and
          * some almost-clones) can provide hooks to make that behave.
+         *
+         * Note that ACPI doesn't preclude putting these registers into
+         * "extended" areas of the chip, including some that we won't yet
+         * expect CMOS_READ and friends to handle.
          */
         if (info) {
-                cmos_rtc.day_alrm = info->rtc_day_alarm;
-                cmos_rtc.mon_alrm = info->rtc_mon_alarm;
-                cmos_rtc.century = info->rtc_century;
+                if (info->rtc_day_alarm && info->rtc_day_alarm < 128)
+                        cmos_rtc.day_alrm = info->rtc_day_alarm;
+                if (info->rtc_mon_alarm && info->rtc_mon_alarm < 128)
+                        cmos_rtc.mon_alrm = info->rtc_mon_alarm;
+                if (info->rtc_century && info->rtc_century < 128)
+                        cmos_rtc.century = info->rtc_century;
 
                 if (info->wake_on && info->wake_off) {
                         cmos_rtc.wake_on = info->wake_on;
@@ -518,10 +612,13 @@ cmos_do_probe(struct device *dev, struct resource *ports, int rtc_irq)
                 goto cleanup1;
         }
 
-        /* REVISIT optionally make 50 or 114 bytes NVRAM available,
-         * like rtc-ds1553, rtc-ds1742 ... this will often include
-         * registers for century, and day/month alarm.
-         */
+        /* export at least the first block of NVRAM */
+        nvram.size = address_space - NVRAM_OFFSET;
+        retval = sysfs_create_bin_file(&dev->kobj, &nvram);
+        if (retval < 0) {
+                dev_dbg(dev, "can't create nvram file? %d\n", retval);
+                goto cleanup2;
+        }
 
         pr_info("%s: alarms up to one %s%s\n",
                         cmos_rtc.rtc->dev.bus_id,
@@ -536,6 +633,9 @@ cmos_do_probe(struct device *dev, struct resource *ports, int rtc_irq)
 
         return 0;
 
+cleanup2:
+        if (is_valid_irq(rtc_irq))
+                free_irq(rtc_irq, cmos_rtc.rtc);
 cleanup1:
         cmos_rtc.dev = NULL;
         rtc_device_unregister(cmos_rtc.rtc);
@@ -563,6 +663,8 @@ static void __exit cmos_do_remove(struct device *dev)
 
         cmos_do_shutdown();
 
+        sysfs_remove_bin_file(&dev->kobj, &nvram);
+
         if (is_valid_irq(cmos->irq))
                 free_irq(cmos->irq, cmos->rtc);
 
@@ -659,9 +761,12 @@ static int cmos_resume(struct device *dev)
 
 /*----------------------------------------------------------------*/
 
-/* The "CMOS" RTC normally lives on the platform_bus.  On ACPI systems,
- * the device node will always be created as a PNPACPI device.  Plus
- * pre-ACPI PCs probably list it in the PNPBIOS tables.
+/* On non-x86 systems, a "CMOS" RTC lives most naturally on platform_bus.
+ * ACPI systems always list these as PNPACPI devices, and pre-ACPI PCs
+ * probably list them in similar PNPBIOS tables; so PNP is more common.
+ *
+ * We don't use legacy "poke at the hardware" probing.  Ancient PCs that
+ * predate even PNPBIOS should set up platform_bus devices.
  */
 
 #ifdef  CONFIG_PNP