Input: uinput - add new UINPUT_DEV_SETUP and UI_ABS_SETUP ioctl

This adds two new ioctls, UINPUT_DEV_SETUP and UI_ABS_SETUP, that replaces
the old device setup method (by write()'ing "struct uinput_user_dev" to the
node). The old method is not easily extendable and requires huge payloads.
Furthermore, overloading write() without properly versioned objects is
error-prone.

Therefore, we introduce two new ioctls to replace the old method. These
ioctls support all features of the old method, plus a "resolution" field
for absinfo. Furthermore, it's properly forward-compatible to new ABS codes
and a growing "struct input_absinfo" structure.

UI_ABS_SETUP also allows user-space to skip unknown axes if not set. There
is no need to copy the whole array temporarily into the kernel, but instead
the caller issues several ioctl where we copy each value manually.

Signed-off-by: David Herrmann <[e-mail]>
Signed-off-by: Benjamin Tissoires <[e-mail]>
Reviewed-by: David Herrmann <[e-mail]>
Signed-off-by: Dmitry Torokhov <[e-mail]>

drivers/input/misc/uinput.c

···
 	return 0;
 }
 
-static int uinput_setup_device(struct uinput_device *udev,
-			       const char __user *buffer, size_t count)
+static int uinput_dev_setup(struct uinput_device *udev,
+			    struct uinput_setup __user *arg)
+{
+	struct uinput_setup setup;
+	struct input_dev *dev;
+	int retval;
+
+	if (udev->state == UIST_CREATED)
+		return -EINVAL;
+
+	if (copy_from_user(&setup, arg, sizeof(setup)))
+		return -EFAULT;
+
+	if (!setup.name[0])
+		return -EINVAL;
+
+	dev = udev->dev;
+	dev->id = setup.id;
+	udev->ff_effects_max = setup.ff_effects_max;
+
+	kfree(dev->name);
+	dev->name = kstrndup(setup.name, UINPUT_MAX_NAME_SIZE, GFP_KERNEL);
+	if (!dev->name)
+		return -ENOMEM;
+
+	retval = uinput_validate_absbits(dev);
+	if (retval < 0)
+		return retval;
+
+	udev->state = UIST_SETUP_COMPLETE;
+	return 0;
+}
+
+static int uinput_abs_setup(struct uinput_device *udev,
+			    struct uinput_setup __user *arg, size_t size)
+{
+	struct uinput_abs_setup setup = {};
+	struct input_dev *dev;
+
+	if (size > sizeof(setup))
+		return -E2BIG;
+
+	if (udev->state == UIST_CREATED)
+		return -EINVAL;
+
+	if (copy_from_user(&setup, arg, size))
+		return -EFAULT;
+
+	if (setup.code > ABS_MAX)
+		return -ERANGE;
+
+	dev = udev->dev;
+
+	input_alloc_absinfo(dev);
+	if (!dev->absinfo)
+		return -ENOMEM;
+
+	set_bit(setup.code, dev->absbit);
+	dev->absinfo[setup.code] = setup.absinfo;
+
+	/*
+	 * We restore the state to UIST_NEW_DEVICE because the user has to call
+	 * UI_DEV_SETUP in the last place before UI_DEV_CREATE to check the
+	 * validity of the absbits.
+	 */
+	udev->state = UIST_NEW_DEVICE;
+	return 0;
+}
+
+/* legacy setup via write() */
+static int uinput_setup_device_legacy(struct uinput_device *udev,
+				      const char __user *buffer, size_t count)
 {
 	struct uinput_user_dev	*user_dev;
 	struct input_dev	*dev;
···
 
 	retval = udev->state == UIST_CREATED ?
 			uinput_inject_events(udev, buffer, count) :
-			uinput_setup_device(udev, buffer, count);
+			uinput_setup_device_legacy(udev, buffer, count);
 
 	mutex_unlock(&udev->mutex);
 
···
 			uinput_destroy_device(udev);
 			goto out;
 
+		case UI_DEV_SETUP:
+			retval = uinput_dev_setup(udev, p);
+			goto out;
+
+		/* UI_ABS_SETUP is handled in the variable size ioctls */
+
 		case UI_SET_EVBIT:
 			retval = uinput_set_bit(arg, evbit, EV_MAX);
 			goto out;
···
 		}
 		name = dev_name(&udev->dev->dev);
 		retval = uinput_str_to_user(p, name, size);
+		goto out;
+
+	case UI_ABS_SETUP & ~IOCSIZE_MASK:
+		retval = uinput_abs_setup(udev, p, size);
 		goto out;
 	}
 

include/linux/uinput.h

···
  * Author: Aristeu Sergio Rozanski Filho <[e-mail]>
  *
  * Changes/Revisions:
+ *	0.5	08/13/2015 (David Herrmann <[e-mail]> &
+ *			    Benjamin Tissoires <[e-mail]>)
+ *		- add UI_DEV_SETUP ioctl
+ *		- add UI_ABS_SETUP ioctl
+ *		- add UI_GET_VERSION ioctl
  *	0.4	01/09/2014 (Benjamin Tissoires <[e-mail]>)
  *		- add UI_GET_SYSNAME ioctl
  *	0.3	24/05/2006 (Anssi Hannula <anssi.hannulagmail.com>)

include/uapi/linux/uinput.h

···
  * Author: Aristeu Sergio Rozanski Filho <[e-mail]>
  *
  * Changes/Revisions:
+ *	0.5	08/13/2015 (David Herrmann <[e-mail]> &
+ *			    Benjamin Tissoires <[e-mail]>)
+ *		- add UI_DEV_SETUP ioctl
+ *		- add UI_ABS_SETUP ioctl
+ *		- add UI_GET_VERSION ioctl
  *	0.4	01/09/2014 (Benjamin Tissoires <[e-mail]>)
  *		- add UI_GET_SYSNAME ioctl
  *	0.3	24/05/2006 (Anssi Hannula <anssi.hannulagmail.com>)
···
 #include <linux/types.h>
 #include <linux/input.h>
 
-#define UINPUT_VERSION		4
-
+#define UINPUT_VERSION		5
+#define UINPUT_MAX_NAME_SIZE	80
 
 struct uinput_ff_upload {
 	__u32			request_id;
···
 #define UINPUT_IOCTL_BASE	'U'
 #define UI_DEV_CREATE		_IO(UINPUT_IOCTL_BASE, 1)
 #define UI_DEV_DESTROY		_IO(UINPUT_IOCTL_BASE, 2)
+
+struct uinput_setup {
+	struct input_id id;
+	char name[UINPUT_MAX_NAME_SIZE];
+	__u32 ff_effects_max;
+};
+
+/**
+ * UI_DEV_SETUP - Set device parameters for setup
+ *
+ * This ioctl sets parameters for the input device to be created. It must be
+ * issued *before* calling UI_DEV_CREATE or it will fail. This ioctl supersedes
+ * the old "struct uinput_user_dev" method, which wrote this data via write().
+ * To actually set the absolute axes, you also need to call the ioctl
+ * UI_ABS_SETUP *before* calling this ioctl.
+ *
+ * This ioctl takes a "struct uinput_setup" object as argument. The fields of
+ * this object are as follows:
+ *              id: See the description of "struct input_id". This field is
+ *                  copied unchanged into the new device.
+ *            name: This is used unchanged as name for the new device.
+ *  ff_effects_max: This limits the maximum numbers of force-feedback effects.
+ *                  See below for a description of FF with uinput.
+ *
+ * This ioctl can be called multiple times and will overwrite previous values.
+ * If this ioctl fails with -EINVAL, you're recommended to use the old
+ * "uinput_user_dev" method via write() as fallback, in case you run on an old
+ * kernel that does not support this ioctl.
+ *
+ * This ioctl may fail with -EINVAL if it is not supported or if you passed
+ * incorrect values, -ENOMEM if the kernel runs out of memory or -EFAULT if the
+ * passed uinput_setup object cannot be read/written.
+ * If this call fails, partial data may have already been applied to the
+ * internal device.
+ */
+#define UI_DEV_SETUP _IOW(UINPUT_IOCTL_BASE, 3, struct uinput_setup)
+
+struct uinput_abs_setup {
+	__u16  code; /* axis code */
+	/* __u16 filler; */
+	struct input_absinfo absinfo;
+};
+
+/**
+ * UI_ABS_SETUP - Set absolute axis information for the device to setup
+ *
+ * This ioctl sets one absolute axis information for the input device to be
+ * created. It must be issued *before* calling UI_DEV_SETUP and UI_DEV_CREATE
+ * for every absolute axis the device exports.
+ * This ioctl supersedes the old "struct uinput_user_dev" method, which wrote
+ * part of this data and the content of UI_DEV_SETUP via write().
+ *
+ * This ioctl takes a "struct uinput_abs_setup" object as argument. The fields
+ * of this object are as follows:
+ *            code: The corresponding input code associated with this axis
+ *                  (ABS_X, ABS_Y, etc...)
+ *         absinfo: See "struct input_absinfo" for a description of this field.
+ *                  This field is copied unchanged into the kernel for the
+ *                  specified axis. If the axis is not enabled via
+ *                  UI_SET_ABSBIT, this ioctl will enable it.
+ *
+ * This ioctl can be called multiple times and will overwrite previous values.
+ * If this ioctl fails with -EINVAL, you're recommended to use the old
+ * "uinput_user_dev" method via write() as fallback, in case you run on an old
+ * kernel that does not support this ioctl.
+ *
+ * This ioctl may fail with -EINVAL if it is not supported or if you passed
+ * incorrect values, -ENOMEM if the kernel runs out of memory or -EFAULT if the
+ * passed uinput_setup object cannot be read/written.
+ * If this call fails, partial data may have already been applied to the
+ * internal device.
+ */
+#define UI_ABS_SETUP _IOW(UINPUT_IOCTL_BASE, 4, struct uinput_abs_setup)
 
 #define UI_SET_EVBIT		_IOW(UINPUT_IOCTL_BASE, 100, int)
 #define UI_SET_KEYBIT		_IOW(UINPUT_IOCTL_BASE, 101, int)
···
 #define UI_FF_UPLOAD		1
 #define UI_FF_ERASE		2
 
-#define UINPUT_MAX_NAME_SIZE	80
 struct uinput_user_dev {
 	char name[UINPUT_MAX_NAME_SIZE];
 	struct input_id id;