Date:   Tue, 30 May 2017 15:50:20 +0300
From:   Oleksandr Andrushchenko <andr2000@...il.com>
To:     Dmitry Torokhov <dmitry.torokhov@...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

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?
(I guess MT_TOOL_PALM is not appropriate anyways)
>>>> +				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)
>>>> +
>>>> +		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.
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
>>>> +
>>>> +		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

View attachment "mtouch_v0_review_fixes.patch" of type "text/x-patch" (2380 bytes)

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