From a3922cf7f02feac88a80995cef5e843aafdd970b Mon Sep 17 00:00:00 2001

From: Peter Hutterer <peter.hutterer@who-t.net>

Date: Wed, 1 Jun 2016 14:38:54 +1000

Subject: [PATCH xserver] Allow compile-time selection of a fallback input

 driver

A new --with-fallback-input-driver=foo option allows selecting a

fallback driver for the server if the driver configured for the device

is not found.  Note that this only applies when the device has a driver

assigned and that module fails to load, devices without a driver are

ignored as usual.

This avoids the situation where a configuration assigns e.g. the

synaptics driver but that driver is not available on the system,

resulting in a dead device. A fallback driver can at least provides some

functionality.

This becomes more important as we move towards making other driver true

leaf nodes that can be installed/uninstalled as requested. Specifically,

wacom and synaptics, a config that assigns either driver should be

viable even when the driver itself is not (yet) installed on the system.

It is up to the distributions to make sure that the fallback driver is

always installed. The fallback driver can be disabled with

--without-fallback-input-driver and is disabled by default on non-Linux

systems because we don't have generic drivers on those platforms.

Default driver on Linux is libinput, evdev is the only other serious

candidate here.

Sample log output:

[  3274.421] (II) config/udev: Adding input device SynPS/2 Synaptics TouchPad (/dev/input/event4)

[  3274.421] (**) SynPS/2 Synaptics TouchPad: Applying InputClass "touchpad weird driver"

[  3274.421] (II) LoadModule: "banana"

[  3274.422] (WW) Warning, couldn't open module banana

[  3274.422] (II) UnloadModule: "banana"

[  3274.422] (II) Unloading banana

[  3274.422] (EE) Failed to load module "banana" (module does not exist, 0)

[  3274.422] (EE) No input driver matching `banana'

[  3274.422] (II) Falling back to input driver `libinput'

.. server proceeds to assign libinput, init the device, world peace and rainbows

everywhere, truly what a sight. Shame about the banana though.

Reviewed-by: Adam Jackson <ajax@redhat.com>

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

(cherry picked from commit c69bd15e00aea2610834d05f63777f9bf20eca34)

---

 configure.ac                   | 19 +++++++++++++++++++

 hw/xfree86/common/xf86Xinput.c | 39 +++++++++++++++++++++++++++++++--------

 include/xorg-config.h.in       |  3 +++

 3 files changed, 53 insertions(+), 8 deletions(-)

diff --git a/configure.ac b/configure.ac

index 868e859..dea8edd 100644

--- a/configure.ac

+++ b/configure.ac

@@ -493,6 +493,25 @@ AC_ARG_ENABLE(listen-local,  AS_HELP_STRING([--disable-listen-local],

                                             [Listen on local by default (default:enabled)]),

                                 [LISTEN_LOCAL=$enableval], [LISTEN_LOCAL=yes])

+case $host_os in

+    linux*)

+        FALLBACK_INPUT_DRIVER="libinput"

+        ;;

+    *)

+        FALLBACK_INPUT_DRIVER=""

+        ;;

+esac

+AC_ARG_WITH(fallback-input-driver,

+            AC_HELP_STRING([--with-fallback-input-driver=$FALLBACK_INPUT_DRIVER],

+                           [Input driver fallback if the requested driver for a device is unavailable]),

+                           [ FALLBACK_INPUT_DRIVER=$withval ], [])

+if test "x$FALLBACK_INPUT_DRIVER" = "xno"; then

+    FALLBACK_INPUT_DRIVER=""

+fi

+AC_MSG_CHECKING([for fallback input driver])

+AC_MSG_RESULT([$FALLBACK_INPUT_DRIVER])

+AC_DEFINE_UNQUOTED(FALLBACK_INPUT_DRIVER, ["$FALLBACK_INPUT_DRIVER"], [ Fallback input driver ])

+

 dnl Determine font path

 XORG_FONTROOTDIR

 XORG_FONTSUBDIR(FONTMISCDIR, fontmiscdir, misc)

diff --git a/hw/xfree86/common/xf86Xinput.c b/hw/xfree86/common/xf86Xinput.c

index c56a2b9..44f4818 100644

--- a/hw/xfree86/common/xf86Xinput.c

+++ b/hw/xfree86/common/xf86Xinput.c

@@ -819,6 +819,22 @@ xf86stat(const char *path, int *maj, int *min)

     *min = minor(st.st_rdev);

 }

+static inline InputDriverPtr

+xf86LoadInputDriver(const char *driver_name)

+{

+    InputDriverPtr drv = NULL;

+

+    /* Memory leak for every attached device if we don't

+     * test if the module is already loaded first */

+    drv = xf86LookupInputDriver(driver_name);

+    if (!drv) {

+        if (xf86LoadOneModule(driver_name, NULL))

+            drv = xf86LookupInputDriver(driver_name);

+    }

+

+    return drv;

+}

+

 /**

  * Create a new input device, activate and enable it.

  *

@@ -845,16 +861,23 @@ xf86NewInputDevice(InputInfoPtr pInfo, DeviceIntPtr *pdev, BOOL enable)

     int rval;

     char *path = NULL;

-    /* Memory leak for every attached device if we don't

-     * test if the module is already loaded first */

-    drv = xf86LookupInputDriver(pInfo->driver);

-    if (!drv)

-        if (xf86LoadOneModule(pInfo->driver, NULL))

-            drv = xf86LookupInputDriver(pInfo->driver);

+    drv = xf86LoadInputDriver(pInfo->driver);

     if (!drv) {

         xf86Msg(X_ERROR, "No input driver matching `%s'\n", pInfo->driver);

-        rval = BadName;

-        goto unwind;

+

+        if (strlen(FALLBACK_INPUT_DRIVER) > 0) {

+            xf86Msg(X_INFO, "Falling back to input driver `%s'\n",

+                    FALLBACK_INPUT_DRIVER);

+            drv = xf86LoadInputDriver(FALLBACK_INPUT_DRIVER);

+            if (drv) {

+                free(pInfo->driver);

+                pInfo->driver = strdup(FALLBACK_INPUT_DRIVER);

+            }

+        }

+        if (!drv) {

+            rval = BadName;

+            goto unwind;

+        }

     }

     path = xf86CheckStrOption(pInfo->options, "Device", NULL);

diff --git a/include/xorg-config.h.in b/include/xorg-config.h.in

index 7c03126..2e2da45 100644

--- a/include/xorg-config.h.in

+++ b/include/xorg-config.h.in

@@ -151,4 +151,7 @@

 /* Support APM/ACPI power management in the server */

 #undef XF86PM

+/* Fallback input driver if the assigned driver fails */

+#undef FALLBACK_INPUT_DRIVER

+

 #endif /* _XORG_CONFIG_H_ */

-- 

2.7.4