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Date: Wed, 7 Jun 2017 10:15:13 +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!
I would appreciate your comments on the below
On 05/31/2017 12:06 PM, Oleksandr Andrushchenko wrote:
> Hi, Dmitry!
>
> On 05/30/2017 07:37 PM, Dmitry Torokhov wrote:
>> 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?
> But it is a finger :) we are multi-touch, not multi pen
>
> Besides, that, if I am about to implement pen support
> (which I still not convinced we really need), how will I
> do that?
> My understanding is that I need 2 different slots to report
> the same coordinates for finger and pen. This is because
> input_mt_report_slot_state has a check that if tool has
> changed for the current slot then a new tracking ID is set.
> Do I also need to allocate twice more slots, so I can
> report 2 * num_contacts events simultaneously (one for finger
> and another for pen)?
> That said, I believe we can start with multi-touch support
> and if need be then add pen support as a separate change,
> does that make sense for you?
>>
>>> (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.
> the protocol used between guest and host is a generic one,
> not using Linux types/constants/events.
> So, no PALM/TOOL support is in place
>>>>>>> + 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).
> yes, if embedded system (which is my target) has evtest
> but it definitely does have ioctl though
>>>>>>> +
>>>>>>> + 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.
> done, thank you
>>>>>>> +
>>>>>>> + 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?
> there is a ring buffer between host and guest,
> so there is always a possibility (rather small I believe)
> that the buffer overruns. Do you think I need INPUT_MT_DROP_UNUSED or
> we can live without it?
>>
>> 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
>>>
>>
> Thank you,
> Oleksandr
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