Message-ID: <20170530163708.GA12922@dtor-ws>
Date:   Tue, 30 May 2017 09:37:08 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Oleksandr Andrushchenko <andr2000@...il.com>
Cc:     xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        linux-input@...r.kernel.org, joculator@...il.com, al1img@...il.com,
        vlad.babchuk@...il.com, andrii.anisov@...il.com,
        olekstysh@...il.com, boris.ostrovsky@...cle.com, jgross@...e.com,
        Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
Subject: Re: [PATCH 2/2] xen/input: add multi-touch support

On Tue, May 30, 2017 at 03:50:20PM +0300, Oleksandr Andrushchenko wrote:
> Hi, Dmitry!
> 
> On 05/30/2017 08:51 AM, Dmitry Torokhov wrote:
> >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@...m.com>
> >>>>
> >>>>Extend xen_kbdfront to provide multi-touch support
> >>>>to unprivileged domains.
> >>>>
> >>>>Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
> >>>>---
> >>>>  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.
> >
> agree, removed "unlikely"
> >>>>+				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.
> I think that for multi-touch MT_TOOL_FINGER is enough
> any reason we would also want MT_TOOL_PEN here?

Why would not you? Let's say you have a drawing application running in
guest that can make use of tool types. Why would not you want to tell it
that the tool user is currently using is in fact a pen and not finger?

> (I guess MT_TOOL_PALM is not appropriate anyways)

Depends on if you do straight pass-through from the host side or not. If
you stack does palm rejection before passing the data through then you
would not see MT_TOOL_PALM in guest.

> >>>>+				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?
> we can, but I see no harm in 1. what is more, this may
> allow guests to emulate more pointing devices
> but, if you insist, then I will add appropriate code to
> reject if number of contacts is less then 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...
> I have removed module parameters (the only use of those
> was to be able to see configured width and height on
> guest side, but this is minor)

evtest would show it to you. Or you can query input device yourself
(EVIOCGABS iotcl).

> >>>>+
> >>>>+		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);

Please make it
		input_set_capability(mtouch, EV_KEY, BTN_TOUCH);

and drop all __set_bit()s.

> >>>>+
> >>>>+		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.
> done
> >  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.
> done, I will use INPUT_MT_DIRECT | INPUT_MT_DROP_UNUSED

Does that mean that your backend does not reliably report release of
contacts?

Thanks.

> >>>>+
> >>>>+		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.
> >
> 
> For your convenience I am attaching the changes I am about
> to put into v1 of the series:
>  - remove unlikely
>  - remove module parameters
>  - error handling for input_mt_init_slots
>  - let userspace better chance of figuring how to handle the device
> 
> Thank you,
> Oleksandr

> From e76506c55846e2bb4ccbafa430642e368643e51d Mon Sep 17 00:00:00 2001
> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
> Date: Tue, 30 May 2017 14:49:58 +0300
> Subject: [PATCH] Fix: remove unlikely Fix: remove module paramters Fix: error
>  handling for input_mt_init_slots Fix: let userspace better chance of figuring
>  how to handle the device
> 
> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
> ---
>  drivers/input/misc/xen-kbdfront.c | 21 ++++++++++-----------
>  1 file changed, 10 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/input/misc/xen-kbdfront.c b/drivers/input/misc/xen-kbdfront.c
> index 8266ef948a06..273d786a19cd 100644
> --- a/drivers/input/misc/xen-kbdfront.c
> +++ b/drivers/input/misc/xen-kbdfront.c
> @@ -51,12 +51,6 @@ 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)");
> -
>  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 *);
> @@ -114,8 +108,8 @@ static irqreturn_t input_handler(int rq, void *dev_id)
>  			dev = info->mtouch;
>  			if (unlikely(!dev))
>  				break;
> -			if (unlikely(event->mtouch.contact_id !=
> -					info->mtouch_cur_contact_id)) {
> +			if (event->mtouch.contact_id !=
> +					info->mtouch_cur_contact_id) {
>  				info->mtouch_cur_contact_id =
>  					event->mtouch.contact_id;
>  				input_mt_slot(dev, event->mtouch.contact_id);
> @@ -327,10 +321,15 @@ static int xenkbd_probe(struct xenbus_device *dev,
>  		input_set_abs_params(mtouch, ABS_MT_PRESSURE,
>  				     0, 255, 0, 0);
>  
> -		input_mt_init_slots(mtouch, num_cont, 0);
> +		ret = input_mt_init_slots(mtouch, num_cont,
> +				INPUT_MT_DIRECT | INPUT_MT_DROP_UNUSED);
> +		if (ret) {
> +			input_free_device(mtouch);
> +			xenbus_dev_fatal(info->xbdev, ret,
> +					 "input_mt_init_slots");
> +			goto error;
> +		}
>  
> -		mtouch_size[KPARAM_MT_X] = width;
> -		mtouch_size[KPARAM_MT_Y] = height;
>  		info->mtouch_cur_contact_id = -1;
>  
>  		ret = input_register_device(mtouch);
> -- 
> 2.7.4
> 


-- 
Dmitry

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