watchdog: Add a simple mmap() stub for shwdt.
In some applications people have expressed a need for an mmap() method,
so we implement a simple stub for this that maps back a page with the
counter in it.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/drivers/char/watchdog/shwdt.c b/drivers/char/watchdog/shwdt.c
index 7c39f39..e5b8c64 100644
--- a/drivers/char/watchdog/shwdt.c
+++ b/drivers/char/watchdog/shwdt.c
@@ -27,7 +27,7 @@
#include <linux/notifier.h>
#include <linux/ioport.h>
#include <linux/fs.h>
-
+#include <linux/mm.h>
#include <asm/io.h>
#include <asm/uaccess.h>
#include <asm/watchdog.h>
@@ -258,6 +258,55 @@
}
/**
+ * sh_wdt_mmap - map WDT/CPG registers into userspace
+ * @file: file structure for the device
+ * @vma: VMA to map the registers into
+ *
+ * A simple mmap() implementation for the corner cases where the counter
+ * needs to be mapped in userspace directly. Due to the relatively small
+ * size of the area, neighbouring registers not necessarily tied to the
+ * CPG will also be accessible through the register page, so this remains
+ * configurable for users that really know what they're doing.
+ *
+ * Additionaly, the register page maps in the CPG register base relative
+ * to the nearest page-aligned boundary, which requires that userspace do
+ * the appropriate CPU subtype math for calculating the page offset for
+ * the counter value.
+ */
+static int sh_wdt_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ int ret = -ENOSYS;
+
+#ifdef CONFIG_SH_WDT_MMAP
+ unsigned long addr;
+
+ /* Only support the simple cases where we map in a register page. */
+ if (((vma->vm_end - vma->vm_start) != PAGE_SIZE) || vma->vm_pgoff)
+ return -EINVAL;
+
+ /*
+ * Pick WTCNT as the start, it's usually the first register after the
+ * FRQCR, and neither one are generally page-aligned out of the box.
+ */
+ addr = WTCNT & ~(PAGE_SIZE - 1);
+
+ vma->vm_flags |= VM_IO;
+ vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+
+ if (io_remap_pfn_range(vma, vma->vm_start, addr >> PAGE_SHIFT,
+ PAGE_SIZE, vma->vm_page_prot)) {
+ printk(KERN_ERR PFX "%s: io_remap_pfn_range failed\n",
+ __FUNCTION__);
+ return -EAGAIN;
+ }
+
+ ret = 0;
+#endif
+
+ return ret;
+}
+
+/**
* sh_wdt_ioctl - Query Device
* @inode: inode of device
* @file: file handle of device
@@ -342,6 +391,7 @@
.ioctl = sh_wdt_ioctl,
.open = sh_wdt_open,
.release = sh_wdt_close,
+ .mmap = sh_wdt_mmap,
};
static struct watchdog_info sh_wdt_info = {