drivers: char: mem: Make /dev/mem an optional device

Adds Kconfig option CONFIG_DEVMEM that allows the
/dev/mem device to be disabled.

Option defaults to /dev/mem enabled.

Signed-off-by: Rob Ward <robert.ward114@googlemail.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 12 insertions, 1 deletions

diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index efefd12a0f7b..a4af8221751e 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -6,6 +6,15 @@ menu "Character devices"
 
 source "drivers/tty/Kconfig"
 
+config DEVMEM
+        bool "/dev/mem virtual device support"
+        default y
+        help
+          Say Y here if you want to support the /dev/mem device.
+          The /dev/mem device is used to access areas of physical
+          memory.
+          When in doubt, say "Y".
+
 config DEVKMEM
         bool "/dev/kmem virtual device support"
         default y
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 4c58333b4257..7d6778437be0 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -715,7 +715,7 @@ static int open_port(struct inode *inode, struct file *filp)
 #define open_mem        open_port
 #define open_kmem       open_mem
 
-static const struct file_operations mem_fops = {
+static const struct file_operations __maybe_unused mem_fops = {
         .llseek         = memory_lseek,
         .read           = read_mem,
         .write          = write_mem,
@@ -785,7 +785,9 @@ static const struct memdev {
         const struct file_operations *fops;
         struct backing_dev_info *dev_info;
 } devlist[] = {
+#ifdef CONFIG_DEVMEM
          [1] = { "mem", 0, &mem_fops, &directly_mappable_cdev_bdi },
+#endif
 #ifdef CONFIG_DEVKMEM
          [2] = { "kmem", 0, &kmem_fops, &directly_mappable_cdev_bdi },
 #endif