[PATCH] fb: udl: fix build without CONFIG_FB_DEFERRED_IO

[Arnd Bergmann <arnd@arndb.de>]

A cleanup in v4.8 dropped several dependencies, but caused the udl driver
to fail building when CONFIG_FB_DEFERRED_IO is not set:

drivers/gpu/drm/udl/udl_fb.c: In function 'udl_fb_open':
drivers/gpu/drm/udl/udl_fb.c:206:23: error: 'struct fb_info' has no member named 'fbdefio'
  if (fb_defio && (info->fbdefio == NULL)) {
                       ^~

This adds an #ifdef check around the code that fails. We know this
is safe because it always checks info->fbdefio for being non-NULL,
and that member is not defined here.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: c0f0c177b5a9 ("drm/udl: make fbdev support really optional")
---
 drivers/gpu/drm/udl/udl_fb.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/udl/udl_fb.c b/drivers/gpu/drm/udl/udl_fb.c
index d5df555aeba0..fec47733e57e 100644
--- a/drivers/gpu/drm/udl/udl_fb.c
+++ b/drivers/gpu/drm/udl/udl_fb.c
@@ -24,11 +24,14 @@
 
 #define DL_DEFIO_WRITE_DELAY    (HZ/20) /* fb_deferred_io.delay in jiffies */
 
-static int fb_defio = 0;  /* Optionally enable experimental fb_defio mmap support */
 static int fb_bpp = 16;
 
 module_param(fb_bpp, int, S_IWUSR | S_IRUSR | S_IWGRP | S_IRGRP);
+
+#ifdef CONFIG_FB_DEFERRED_IO
+static int fb_defio = 0;  /* Optionally enable experimental fb_defio mmap support */
 module_param(fb_defio, int, S_IWUSR | S_IRUSR | S_IWGRP | S_IRGRP);
+#endif
 
 struct udl_fbdev {
 	struct drm_fb_helper helper;
@@ -203,6 +206,7 @@ static int udl_fb_open(struct fb_info *info, int user)
 
 	ufbdev->fb_count++;
 
+#ifdef CONFIG_FB_DEFERRED_IO
 	if (fb_defio && (info->fbdefio == NULL)) {
 		/* enable defio at last moment if not disabled by client */
 
@@ -218,6 +222,7 @@ static int udl_fb_open(struct fb_info *info, int user)
 		info->fbdefio = fbdefio;
 		fb_deferred_io_init(info);
 	}
+#endif
 
 	pr_notice("open /dev/fb%d user=%d fb_info=%p count=%d\n",
 		  info->node, user, info, ufbdev->fb_count);
@@ -235,12 +240,14 @@ static int udl_fb_release(struct fb_info *info, int user)
 
 	ufbdev->fb_count--;
 
+#ifdef CONFIG_FB_DEFERRED_IO
 	if ((ufbdev->fb_count == 0) && (info->fbdefio)) {
 		fb_deferred_io_cleanup(info);
 		kfree(info->fbdefio);
 		info->fbdefio = NULL;
 		info->fbops->fb_mmap = udl_fb_mmap;
 	}
+#endif
 
 	pr_warn("released /dev/fb%d user=%d count=%d\n",
 		info->node, user, ufbdev->fb_count);
-- 
2.9.0