1 files changed, 37 insertions, 0 deletions

diff --git a/src/touch-caps.c b/src/touch-caps.c
index 7f243c5..a51912c 100644
--- a/src/touch-caps.c
+++ b/src/touch-caps.c
@@ -21,6 +21,7 @@
  ****************************************************************************/
 
 #include <grail-touch.h>
+#include <errno.h>
 #include <math.h>
 
 /* see mtdev-mapping.h */
@@ -29,6 +30,42 @@
 #define MTDEV_ORIENTATION       4
 #define MTDEV_PRESSURE          10
 
+#define SYSCALL(call) while (((call) == -1) && (errno == EINTR))
+
+static const int bits_per_long = 8 * sizeof(long);
+
+static inline int nlongs(int nbit)
+{
+        return (nbit + bits_per_long - 1) / bits_per_long;
+}
+
+static inline int getbit(const unsigned long *map, int key)
+{
+        return (map[key / bits_per_long] >> (key % bits_per_long)) & 0x01;
+}
+
+int touch_caps_is_supported(struct touch_dev *dev, int fd)
+{
+        unsigned long keybits[nlongs(KEY_MAX)];
+        unsigned long absbits[nlongs(ABS_MAX)];
+        int rc;
+
+        if (dev->mtdev.caps.has_mtdata)
+                return 1;
+
+        SYSCALL(rc = ioctl(fd, EVIOCGBIT(EV_KEY, sizeof(keybits)), keybits));
+        if (rc < 0)
+                return 0;
+        SYSCALL(rc = ioctl(fd, EVIOCGBIT(EV_ABS, sizeof(absbits)), absbits));
+        if (rc < 0)
+                return 0;
+
+        return getbit(absbits, ABS_X) &&
+                getbit(absbits, ABS_Y) &&
+                getbit(keybits, BTN_TOUCH) &&
+                getbit(keybits, BTN_TOOL_DOUBLETAP);
+}
+
 void touch_caps_init(struct touch_dev *dev)
 {
         const struct mtdev_caps *mt = &dev->mtdev.caps;