Staging: udlfb: explicit dependencies and warnings

Specify Kconfig dependencies, and include warnings for building as a module

udlfb is dependent on FB_DEFERRED_IO, FB_SYS_*, and FB_MODE_HELPERS

Because many kernels do not include defio (which cannot be built
as a module), yet users want to be able to build udlfb as a module later,
udlfb has ifdefs and these dependency warnings to help udlfb build with or
without certain dependencies, but also print warnings for any lost function.

Even though this kind of flexibility isn't common, we've gotten feedback
from a significant portion of users that they were frustrated without it.

Signed-off-by: Bernie Thompson <bernie@plugable.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/staging/udlfb/udlfb.c b/drivers/staging/udlfb/udlfb.c
index 939b8faba0ff..baad03a8a873 100644
--- a/drivers/staging/udlfb/udlfb.c
+++ b/drivers/staging/udlfb/udlfb.c
@@ -56,6 +56,20 @@ static struct usb_device_id id_table[] = {
 };
 MODULE_DEVICE_TABLE(usb, id_table);
 
+#ifndef CONFIG_FB_DEFERRED_IO
+#warning message "kernel FB_DEFFERRED_IO option to support generic fbdev apps"
+#endif
+
+#ifndef CONFIG_FB_SYS_IMAGEBLIT
+#ifndef CONFIG_FB_SYS_IMAGEBLIT_MODULE
+#warning message "FB_SYS_* in kernel or module option to support fb console"
+#endif
+#endif
+
+#ifndef CONFIG_FB_MODE_HELPERS
+#warning message "kernel FB_MODE_HELPERS required. Expect build break"
+#endif
+
 /* dlfb keeps a list of urbs for efficient bulk transfers */
 static void dlfb_urb_completion(struct urb *urb);
 static struct urb *dlfb_get_urb(struct dlfb_data *dev);