linux-kernel - Re: [Xen-devel] [PATCH v2] xen, input: try to read screen resolution for xen-kbdfront

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Date:   Mon, 30 Jan 2017 13:27:29 +0200
From:   Oleksandr Andrushchenko <andr2000@...il.com>
To:     Juergen Gross <jgross@...e.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        xen-devel@...ts.xenproject.org
Subject: Re: [Xen-devel] [PATCH v2] xen, input: try to read screen resolution
 for xen-kbdfront

On 01/30/2017 01:23 PM, Juergen Gross wrote:
> On 27/01/17 17:10, Dmitry Torokhov wrote:
>> On January 27, 2017 12:31:19 AM PST, Juergen Gross <jgross@...e.com> wrote:
>>> On 27/01/17 09:26, Oleksandr Andrushchenko wrote:
>>>> On 01/27/2017 10:14 AM, Juergen Gross wrote:
>>>>> On 27/01/17 08:53, Oleksandr Andrushchenko wrote:
>>>>>> On 01/27/2017 09:46 AM, Juergen Gross wrote:
>>>>>>> On 27/01/17 08:21, Oleksandr Andrushchenko wrote:
>>>>>>>> On 01/27/2017 09:12 AM, Juergen Gross wrote:
>>>>>>>>> Instead of using the default resolution of 800*600 for the
>>> pointing
>>>>>>>>> device of xen-kbdfront try to read the resolution of the
>>> (virtual)
>>>>>>>>> framebuffer device. Use the default as fallback only.
>>>>>>>>>
>>>>>>>>> Signed-off-by: Juergen Gross <jgross@...e.com>
>>>>>>>>> ---
>>>>>>>>> V2: get framebuffer resolution only if CONFIG_FB (Dmitry
>>> Torokhov)
>>>>>>>>> ---
>>>>>>>>>      drivers/input/misc/xen-kbdfront.c | 15 ++++++++++++---
>>>>>>>>>      1 file changed, 12 insertions(+), 3 deletions(-)
>>>>>>>>>
>>>>>>>>> diff --git a/drivers/input/misc/xen-kbdfront.c
>>>>>>>>> b/drivers/input/misc/xen-kbdfront.c
>>>>>>>>> index 3900875..3aae9b4 100644
>>>>>>>>> --- a/drivers/input/misc/xen-kbdfront.c
>>>>>>>>> +++ b/drivers/input/misc/xen-kbdfront.c
>>>>>>>>> @@ -16,6 +16,7 @@
>>>>>>>>>      #include <linux/kernel.h>
>>>>>>>>>      #include <linux/errno.h>
>>>>>>>>>      #include <linux/module.h>
>>>>>>>>> +#include <linux/fb.h>
>>>>>>>>>      #include <linux/input.h>
>>>>>>>>>      #include <linux/slab.h>
>>>>>>>>>      @@ -108,7 +109,7 @@ static irqreturn_t input_handler(int rq,
>>> void
>>>>>>>>> *dev_id)
>>>>>>>>>      static int xenkbd_probe(struct xenbus_device *dev,
>>>>>>>>>                        const struct xenbus_device_id *id)
>>>>>>>>>      {
>>>>>>>>> -    int ret, i;
>>>>>>>>> +    int ret, i, width, height;
>>>>>>>>>          unsigned int abs;
>>>>>>>>>          struct xenkbd_info *info;
>>>>>>>>>          struct input_dev *kbd, *ptr;
>>>>>>>>> @@ -173,9 +174,17 @@ static int xenkbd_probe(struct
>>> xenbus_device
>>>>>>>>> *dev,
>>>>>>>>>          ptr->id.product = 0xfffe;
>>>>>>>>>            if (abs) {
>>>>>>>>> +        width = XENFB_WIDTH;
>>>>>>>>> +        height = XENFB_HEIGHT;
>>>>>>>>> +#ifdef CONFIG_FB
>>>>>>>>> +        if (registered_fb[0]) {
>>>>>>>> This still will not help if FB gets registered after kbd+ptr
>>>>>>> Hmm, so you think I should add a call to fb_register_client() to
>>> get
>>>>>>> events for new registered framebuffer devices?
>>>>>> yes, but also pay attention to CONFIG_FB_NOTIFY: you may still
>>>>>> end up w/o notification.
>>>>> Okay, that's not worse than today.
>>>> agree
>>>>>>> This would probably work. I'll have a try.
>>>>>>>
>>>>>>>
>>>>>>> Thanks,
>>>>>>>
>>>>>>> Juergen
>>>>>> My bigger concern here is that we try to tie keyboard and pointer
>>> device
>>>>>> to the framebuffer. IMO, these are independent parts of the system
>>> and
>>>>>> the relation
>>>>>> depends on the use-case. One can have graphics enabled w/o
>>> framebuffer
>>>>>> at all, e.g.
>>>>>> DRM/KMS + OpenGLES + Weston + kbd + ptr...
>>>>> Again: that's a use case which will work as today. The current
>>> defaults
>>>>> are being used.
>>>>>
>>>>> The question is whether we should add a module parameter switching
>>> off
>>>>> the automatic adaption of the resolution as there might be use cases
>>>>> where we don't want this feature.
>>>> I think for those who doesn't want this resolution there is
>>>> still a possibility to change it on backend's XenbusStateConnected
>>>> So, no need for module parameter, IMO
>>> Fine.
>>>
>>> I'll send V3 soon.
>> How about you do the axis adjustment from userspace (udev rule), and leave kernel as is?
> Hmm, is this a good idea?
>
> I'd need a udev rule to trigger when either the pointing device or a
> new frame buffer is showing up. In both cases I need to read the
> geometry of the frame buffer (in case it exists) and set the geometry
> of the pointing device (in case it exists) to the same values. This
> seems to be much more complicated than the required changes in the
> driver.
>
> I could be wrong, of course, especially as I'm no expert in writing
> udev rules. :-)
And you may also end up with thin Dom0 w/o udev at all...
>
> Juergen