UIO: Add alignment warnings for uio-mem

This patch adds an "offset" attribute for UIO mappings. It shows the
difference between the actual start address of the memory and the start
address of the page.

Signed-off-by: Hans J. Koch <hjk@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 8 insertions, 0 deletions

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index 9ac22c7c3854..557e73ef5884 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -67,6 +67,11 @@ static ssize_t map_size_show(struct uio_mem *mem, char *buf)
         return sprintf(buf, "0x%lx\n", mem->size);
 }
 
+static ssize_t map_offset_show(struct uio_mem *mem, char *buf)
+{
+        return sprintf(buf, "0x%lx\n", mem->addr & ~PAGE_MASK);
+}
+
 struct uio_sysfs_entry {
         struct attribute attr;
         ssize_t (*show)(struct uio_mem *, char *);
@@ -77,10 +82,13 @@ static struct uio_sysfs_entry addr_attribute =
         __ATTR(addr, S_IRUGO, map_addr_show, NULL);
 static struct uio_sysfs_entry size_attribute =
         __ATTR(size, S_IRUGO, map_size_show, NULL);
+static struct uio_sysfs_entry offset_attribute =
+        __ATTR(offset, S_IRUGO, map_offset_show, NULL);
 
 static struct attribute *attrs[] = {
         &addr_attribute.attr,
         &size_attribute.attr,
+        &offset_attribute.attr,
         NULL,   /* need to NULL terminate the list of attributes */
 };