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Subject[RFC][PATCH] input: Introduce device information ioctl
Date
Today, userspace sets up an input device based on the data it emits.
This is not always enough; a tablet and a touchscreen may emit exactly
the same data, for instance, but the former should be set up with a
pointer whereas the latter does not need to. Recently, a new type of
touchpad has emerged where the buttons are under the pad, which changes
handling logic without changing the emitted data. This patch introduces
a new ioctl, EVIOCGDEVINFO, which allows userspace to extract information
about the device resulting in proper setup.

Suggested-by: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Cc: Ping Cheng <pingc@wacom.com>
Cc: Chris Bagwell <chris@cnpbagwell.com>
---
Hi all,
Here is a patch attempting to formulate Dmitry's device type idea. It
compiles, but further testing awaits a general consesus on the device
types and capabilities to start out with. Are the ones listed here apt
for the job?

Cheers,
Henrik

drivers/input/evdev.c | 6 ++++++
include/linux/input.h | 34 ++++++++++++++++++++++++++++++++++
2 files changed, 40 insertions(+), 0 deletions(-)
diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index e3f7fc6..db78592 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -632,6 +632,12 @@ static long evdev_do_ioctl(struct file *file, unsigned int cmd,
return -EFAULT;
return 0;

+ case EVIOCGDEVINFO:
+ if (copy_to_user(p, &dev->devinfo,
+ sizeof(struct input_devinfo)))
+ return -EFAULT;
+ return 0;
+
case EVIOCGREP:
if (!test_bit(EV_REP, dev->evbit))
return -ENOSYS;
diff --git a/include/linux/input.h b/include/linux/input.h
index 6ef4446..8c58d2a 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -57,6 +57,21 @@ struct input_absinfo {
};

/**
+ * struct input_devinfo - device information via EVIOCGDEVINFO ioctl
+ * @types: bitmask of types (DEVTYPE_*) matching this device
+ * @capabilities: bitmask of capabilities (DEVCAPS_*) of this device
+ *
+ * This struct provides information about the device needed for
+ * automatic setup in userspace, such as if the device is direct
+ * (touchscreen) or indirect (touchpad), and if there are other
+ * special considerations, such as the touchpad also being a button.
+ */
+struct input_devinfo {
+ __u32 types;
+ __u32 capabilities;
+};
+
+/**
* struct input_keymap_entry - used by EVIOCGKEYCODE/EVIOCSKEYCODE ioctls
* @scancode: scancode represented in machine-endian form.
* @len: length of the scancode that resides in @scancode buffer.
@@ -91,6 +106,7 @@ struct input_keymap_entry {
#define EVIOCGNAME(len) _IOC(_IOC_READ, 'E', 0x06, len) /* get device name */
#define EVIOCGPHYS(len) _IOC(_IOC_READ, 'E', 0x07, len) /* get physical location */
#define EVIOCGUNIQ(len) _IOC(_IOC_READ, 'E', 0x08, len) /* get unique identifier */
+#define EVIOCGDEVINFO _IOR('E', 0x09, struct input_devinfo) /* get device information */

#define EVIOCGKEY(len) _IOC(_IOC_READ, 'E', 0x18, len) /* get global key state */
#define EVIOCGLED(len) _IOC(_IOC_READ, 'E', 0x19, len) /* get all LEDs */
@@ -108,6 +124,23 @@ struct input_keymap_entry {
#define EVIOCGRAB _IOW('E', 0x90, int) /* Grab/Release device */

/*
+ * Device types
+ */
+
+#define DEVTYPE_KEYBOARD 0
+#define DEVTYPE_MOUSE 1
+#define DEVTYPE_JOYSTICK 2
+#define DEVTYPE_TOUCHPAD 3
+#define DEVTYPE_TABLET 4
+#define DEVTYPE_TOUCHSCREEN 5
+
+/*
+ * Device capabilities
+ */
+
+#define DEVCAPS_PAD_IS_BUTTON 1
+
+/*
* Event types
*/

@@ -1177,6 +1210,7 @@ struct input_dev {
const char *phys;
const char *uniq;
struct input_id id;
+ struct input_devinfo devinfo;

unsigned long evbit[BITS_TO_LONGS(EV_CNT)];
unsigned long keybit[BITS_TO_LONGS(KEY_CNT)];
--
1.7.1


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