On Tue, 16 Feb 2016, Arnd Bergmann wrote:

On Monday 15 February 2016 16:51:08 Stefano Stabellini wrote:

quoted

quoted

diff --git a/drivers/video/fbdev/Kconfig b/drivers/video/fbdev/Kconfig
index 8ea45a5cd806..fd3d6fd290a9 100644
--- a/drivers/video/fbdev/Kconfig
+++ b/drivers/video/fbdev/Kconfig

@@ -2241,6 +2241,7 @@ config FB_VIRTUAL
 config XEN_FBDEV_FRONTEND
      tristate "Xen virtual frame buffer support"
      depends on FB && XEN
+     depends on INPUT || !INPUT_MISC
      select FB_SYS_FILLRECT
      select FB_SYS_COPYAREA
      select FB_SYS_IMAGEBLIT

This looks very hackish. Couldn't we just do the following?

diff --git a/drivers/video/fbdev/Kconfig b/drivers/video/fbdev/Kconfig
index 8ea45a5..3c15f6d 100644
--- a/drivers/video/fbdev/Kconfig
+++ b/drivers/video/fbdev/Kconfig

@@ -2246,7 +2246,7 @@ config XEN_FBDEV_FRONTEND
        select FB_SYS_IMAGEBLIT
        select FB_SYS_FOPS
        select FB_DEFERRED_IO
-       select INPUT_XEN_KBDDEV_FRONTEND if INPUT_MISC
+       select INPUT_XEN_KBDDEV_FRONTEND if (INPUT && INPUT_MISC)
        select XEN_XENBUS_FRONTEND
        default y
        help

No, that doesn't solve the problem:

If XEN_FBDEV_FRONTEND=y, INPUT=m and INPUT_MISC=y, we would still
get INPUT_XEN_KBDDEV_FRONTEND=y, which cannot work because of INPUT=m.

INPUT_MISC already depends on INPUT, so your change has no effect
at all.

Please correct me if I am wrong, but the difference is that with this
change if INPUT=m, then the build system would ask the user whether she
wants to select INPUT_XEN_KBDDEV_FRONTEND as m or y, instead of
unconditionally set INPUT_XEN_KBDDEV_FRONTEND=y.

However it is true that if the users chooses
INPUT_XEN_KBDDEV_FRONTEND=y, then the problem persists.
Maybe we also need:

diff --git a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig
index 1f2337a..303df24 100644
--- a/drivers/input/misc/Kconfig
+++ b/drivers/input/misc/Kconfig

@@ -721,7 +721,7 @@ config INPUT_CMA3000_I2C
 
 config INPUT_XEN_KBDDEV_FRONTEND
 	tristate "Xen virtual keyboard and mouse support"
-	depends on XEN
+	depends on XEN && INPUT
 	default y
 	select XEN_XENBUS_FRONTEND
 	help

Do you have a kernel config with INPUT=m that I can use to test with?