Re: [PATCH 2/2] xen/input: add multi-touch support

[Dmitry Torokhov]

On Fri, Apr 21, 2017 at 09:40:36AM +0300, Oleksandr Andrushchenko wrote:
> Hi, Dmitry!
> 
> On 04/21/2017 05:10 AM, Dmitry Torokhov wrote:
> >Hi Oleksandr,
> >
> >On Thu, Apr 13, 2017 at 02:38:04PM +0300, Oleksandr Andrushchenko wrote:
> >>From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> >>
> >>Extend xen_kbdfront to provide multi-touch support
> >>to unprivileged domains.
> >>
> >>Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
> >>---
> >>  drivers/input/misc/xen-kbdfront.c | 142 +++++++++++++++++++++++++++++++++++++-
> >>  1 file changed, 140 insertions(+), 2 deletions(-)
> >>
> >>diff --git a/drivers/input/misc/xen-kbdfront.c b/drivers/input/misc/xen-kbdfront.c
> >>index 01c27b4c3288..e5d064aaa237 100644
> >>--- a/drivers/input/misc/xen-kbdfront.c
> >>+++ b/drivers/input/misc/xen-kbdfront.c
> >>@@ -17,6 +17,7 @@
> >>  #include <linux/errno.h>
> >>  #include <linux/module.h>
> >>  #include <linux/input.h>
> >>+#include <linux/input/mt.h>
> >>  #include <linux/slab.h>
> >>  #include <asm/xen/hypervisor.h>
> >>@@ -34,11 +35,14 @@
> >>  struct xenkbd_info {
> >>  	struct input_dev *kbd;
> >>  	struct input_dev *ptr;
> >>+	struct input_dev *mtouch;
> >>  	struct xenkbd_page *page;
> >>  	int gref;
> >>  	int irq;
> >>  	struct xenbus_device *xbdev;
> >>  	char phys[32];
> >>+	/* current MT slot/contact ID we are injecting events in */
> >>+	int mtouch_cur_contact_id;
> >>  };
> >>  enum { KPARAM_X, KPARAM_Y, KPARAM_CNT };
> >>@@ -47,6 +51,12 @@ module_param_array(ptr_size, int, NULL, 0444);
> >>  MODULE_PARM_DESC(ptr_size,
> >>  	"Pointing device width, height in pixels (default 800,600)");
> >>+enum { KPARAM_MT_X, KPARAM_MT_Y, KPARAM_MT_CNT };
> >>+static int mtouch_size[KPARAM_MT_CNT] = { XENFB_WIDTH, XENFB_HEIGHT };
> >>+module_param_array(mtouch_size, int, NULL, 0444);
> >>+MODULE_PARM_DESC(ptr_size,
> >>+	"Multi-touch device width, height in pixels (default 800,600)");
> >>+
> >Why do you need separate module parameters for multi-touch device?
> please see below
> >
> >>  static int xenkbd_remove(struct xenbus_device *);
> >>  static int xenkbd_connect_backend(struct xenbus_device *, struct xenkbd_info *);
> >>  static void xenkbd_disconnect_backend(struct xenkbd_info *);
> >>@@ -100,6 +110,60 @@ static irqreturn_t input_handler(int rq, void *dev_id)
> >>  				input_report_rel(dev, REL_WHEEL,
> >>  						 -event->pos.rel_z);
> >>  			break;
> >>+		case XENKBD_TYPE_MTOUCH:
> >>+			dev = info->mtouch;
> >>+			if (unlikely(!dev))
> >>+				break;
> >>+			if (unlikely(event->mtouch.contact_id !=
> >>+					info->mtouch_cur_contact_id)) {
> >Why is this unlikely? Does contact ID changes once in 1000 packets or
> >even less?
> Mu assumption was that regardless of the fact that we are multi-touch
> device still single touches will come in more frequently
> But I can remove *unlikely* if my assumption is not correct

I think the normal expectation is that "unlikely" is supposed for
something that happens once in a blue moon, so I'd rather remove it.

> >>+				info->mtouch_cur_contact_id =
> >>+					event->mtouch.contact_id;
> >>+				input_mt_slot(dev, event->mtouch.contact_id);
> >>+			}
> >>+			switch (event->mtouch.event_type) {
> >>+			case XENKBD_MT_EV_DOWN:
> >>+				input_mt_report_slot_state(dev, MT_TOOL_FINGER,
> >>+							   true);

Should we establish tool event? We have MT_TOOL_PEN, etc.

> >>+				input_event(dev, EV_ABS, ABS_MT_POSITION_X,
> >>+					    event->mtouch.u.pos.abs_x);
> >>+				input_event(dev, EV_ABS, ABS_MT_POSITION_Y,
> >>+					    event->mtouch.u.pos.abs_y);
> >>+				input_event(dev, EV_ABS, ABS_X,
> >>+					    event->mtouch.u.pos.abs_x);
> >>+				input_event(dev, EV_ABS, ABS_Y,
> >>+					    event->mtouch.u.pos.abs_y);
> >>+				break;
> >>+			case XENKBD_MT_EV_UP:
> >>+				input_mt_report_slot_state(dev, MT_TOOL_FINGER,
> >>+							   false);
> >>+				break;
> >>+			case XENKBD_MT_EV_MOTION:
> >>+				input_event(dev, EV_ABS, ABS_MT_POSITION_X,
> >>+					    event->mtouch.u.pos.abs_x);
> >>+				input_event(dev, EV_ABS, ABS_MT_POSITION_Y,
> >>+					    event->mtouch.u.pos.abs_y);
> >>+				input_event(dev, EV_ABS, ABS_X,
> >>+					    event->mtouch.u.pos.abs_x);
> >>+				input_event(dev, EV_ABS, ABS_Y,
> >>+					    event->mtouch.u.pos.abs_y);
> >>+				break;
> >>+			case XENKBD_MT_EV_SYN:
> >>+				input_mt_sync_frame(dev);
> >>+				break;
> >>+			case XENKBD_MT_EV_SHAPE:
> >>+				input_event(dev, EV_ABS, ABS_MT_TOUCH_MAJOR,
> >>+					    event->mtouch.u.shape.major);
> >>+				input_event(dev, EV_ABS, ABS_MT_TOUCH_MINOR,
> >>+					    event->mtouch.u.shape.minor);
> >>+				break;
> >>+			case XENKBD_MT_EV_ORIENT:
> >>+				input_event(dev, EV_ABS, ABS_MT_ORIENTATION,
> >>+					    event->mtouch.u.orientation);
> >>+				break;
> >>+			}
> >>+			/* only report syn when requested */
> >>+			if (event->mtouch.event_type != XENKBD_MT_EV_SYN)
> >>+				dev = NULL;
> >>  		}
> >>  		if (dev)
> >>  			input_sync(dev);
> >>@@ -115,9 +179,9 @@ static int xenkbd_probe(struct xenbus_device *dev,
> >>  				  const struct xenbus_device_id *id)
> >>  {
> >>  	int ret, i;
> >>-	unsigned int abs;
> >>+	unsigned int abs, touch;
> >>  	struct xenkbd_info *info;
> >>-	struct input_dev *kbd, *ptr;
> >>+	struct input_dev *kbd, *ptr, *mtouch;
> >>  	info = kzalloc(sizeof(*info), GFP_KERNEL);
> >>  	if (!info) {
> >>@@ -152,6 +216,17 @@ static int xenkbd_probe(struct xenbus_device *dev,
> >>  		}
> >>  	}
> >>+	touch = xenbus_read_unsigned(dev->nodename,
> >>+				     XENKBD_FIELD_FEAT_MTOUCH, 0);
> >>+	if (touch) {
> >>+		ret = xenbus_write(XBT_NIL, dev->nodename,
> >>+				   XENKBD_FIELD_REQ_MTOUCH, "1");
> >>+		if (ret) {
> >>+			pr_warning("xenkbd: can't request multi-touch");
> >>+			touch = 0;
> >>+		}
> >>+	}
> >>+
> >>  	/* keyboard */
> >>  	kbd = input_allocate_device();
> >>  	if (!kbd)
> >>@@ -208,6 +283,67 @@ static int xenkbd_probe(struct xenbus_device *dev,
> >>  	}
> >>  	info->ptr = ptr;
> >>+	/* multi-touch device */
> >>+	if (touch) {
> >>+		int num_cont, width, height;
> >>+
> >>+		mtouch = input_allocate_device();
> >>+		if (!mtouch)
> >>+			goto error_nomem;
> >>+
> >>+		num_cont = xenbus_read_unsigned(info->xbdev->nodename,
> >>+						XENKBD_FIELD_MT_NUM_CONTACTS,
> >>+						1);

Should we refuse MT devices with number of contacts less than 2?

> >>+		width = xenbus_read_unsigned(info->xbdev->nodename,
> >>+					     XENKBD_FIELD_MT_WIDTH,
> >>+					     XENFB_WIDTH);
> >>+		height = xenbus_read_unsigned(info->xbdev->nodename,
> >>+					      XENKBD_FIELD_MT_HEIGHT,
> >>+					      XENFB_HEIGHT);
> >Curious why you need separate parameters here too...
> This is because mt parameters are different from ptr
> in a way that they are configurable per front driver's
> instance rather than per backend, e.g. in XenStore:
> 
> /local/domain/0/backend/vkbd/1/0/width = "1920"
> /local/domain/0/backend/vkbd/1/0/height = "1080"
> 
> /local/domain/1/device/vkbd/0/multi-touch-width = "1920"
> /local/domain/1/device/vkbd/0/multi-touch-height = "1080"
> /local/domain/1/device/vkbd/0/multi-touch-num-contacts = "10"
> 
> /local/domain/1/device/vkbd/1/multi-touch-width = "800"
> /local/domain/1/device/vkbd/1/multi-touch-height = "600"
> /local/domain/1/device/vkbd/1/multi-touch-num-contacts = "3"
> 
> The main reason for such configuration is that you can
> configure multiple mt input devices even for the same guest
> with different resolutions which may not match those
> configured for ptr.
> (In my use-case I use new displif protocol [1] in conjunction
> with mt input devices and the corresponding backend is not
> QEMU's xenfb)

I see.

> 
> As to module parameters, I added those to be consistent with
> ptr device. Do you think we can live without them and
> do you want me to remove them?

Yes, I think we better. I am also confused by the way you are handling
the module parameters. It looks to me you update them with data passed
from the backend, but never use the data...

> >>+
> >>+		mtouch->name = "Xen Virtual Multi-touch";
> >>+		mtouch->phys = info->phys;
> >>+		mtouch->id.bustype = BUS_PCI;
> >>+		mtouch->id.vendor = 0x5853;
> >>+		mtouch->id.product = 0xfffd;
> >>+
> >>+		__set_bit(EV_ABS, mtouch->evbit);
> >>+		__set_bit(EV_KEY, mtouch->evbit);
> >>+		__set_bit(BTN_TOUCH, mtouch->keybit);
> >>+
> >>+		input_set_abs_params(mtouch, ABS_X,
> >>+				     0, width, 0, 0);
> >>+		input_set_abs_params(mtouch, ABS_Y,
> >>+				     0, height, 0, 0);
> >>+		input_set_abs_params(mtouch, ABS_PRESSURE,
> >>+				     0, 255, 0, 0);
> >>+
> >>+		input_set_abs_params(mtouch, ABS_MT_TOUCH_MAJOR,
> >>+				     0, 255, 0, 0);
> >>+		input_set_abs_params(mtouch, ABS_MT_POSITION_X,
> >>+				     0, width, 0, 0);
> >>+		input_set_abs_params(mtouch, ABS_MT_POSITION_Y,
> >>+				     0, height, 0, 0);
> >>+		input_set_abs_params(mtouch, ABS_MT_PRESSURE,
> >>+				     0, 255, 0, 0);
> >>+
> >>+		input_mt_init_slots(mtouch, num_cont, 0);

We need error handling here. Also, it would be nice if we set INPUT_MT_*
flags here, so that userspace had better chance of figuring how to
handle the device.

> >>+
> >>+		mtouch_size[KPARAM_MT_X] = width;
> >>+		mtouch_size[KPARAM_MT_Y] = height;
> >>+		info->mtouch_cur_contact_id = -1;
> >>+
> >>+		ret = input_register_device(mtouch);
> >>+		if (ret) {
> >>+			input_free_device(mtouch);
> >>+			xenbus_dev_fatal(info->xbdev, ret,
> >>+					 "input_register_device(mtouch)");
> >>+			goto error;
> >>+		}
> >>+		info->mtouch_cur_contact_id = -1;
> >>+		info->mtouch = mtouch;
> >>+	}
> >>+
> >>  	ret = xenkbd_connect_backend(dev, info);
> >>  	if (ret < 0)
> >>  		goto error;
> >>@@ -240,6 +376,8 @@ static int xenkbd_remove(struct xenbus_device *dev)
> >>  		input_unregister_device(info->kbd);
> >>  	if (info->ptr)
> >>  		input_unregister_device(info->ptr);
> >>+	if (info->mtouch)
> >>+		input_unregister_device(info->mtouch);
> >>  	free_page((unsigned long)info->page);
> >>  	kfree(info);
> >>  	return 0;
> >>-- 
> >>2.7.4
> >>


Thanks.

-- 
Dmitry