linux-kernel - Re: [Xen-devel] [PATCH 1/2] xen, input: add xen-kbdfront module parameter for setting resolution

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Message-ID: <0d7df625-27a1-0c1e-49f3-e1d44c09a787@gmail.com>
Date:   Mon, 10 Apr 2017 17:18:20 +0300
From:   Oleksandr Andrushchenko <andr2000@...il.com>
To:     Juergen Gross <jgross@...e.com>, linux-kernel@...r.kernel.org,
        xen-devel@...ts.xenproject.org, linux-input@...r.kernel.org
Cc:     dmitry.torokhov@...il.com
Subject: Re: [Xen-devel] [PATCH 1/2] xen, input: add xen-kbdfront module
 parameter for setting resolution

On 04/10/2017 05:11 PM, Juergen Gross wrote:
> On 10/04/17 16:00, Oleksandr Andrushchenko wrote:
>>
>> On 04/10/2017 04:50 PM, Juergen Gross wrote:
>>> On 10/04/17 15:44, Oleksandr Andrushchenko wrote:
>>>> Hi, Juergen!
>>>>
>>>> On 03/21/2017 07:19 PM, Juergen Gross wrote:
>>>>> Add a parameter for setting the resolution of xen-kbdfront in order to
>>>>> be able to cope with a (virtual) frame buffer of arbitrary resolution.
>>>>>
>>>>> Signed-off-by: Juergen Gross <jgross@...e.com>
>>>>> ---
>>>>>     drivers/input/misc/xen-kbdfront.c | 10 ++++++++--
>>>>>     1 file changed, 8 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/drivers/input/misc/xen-kbdfront.c
>>>>> b/drivers/input/misc/xen-kbdfront.c
>>>>> index 3900875..2df5678 100644
>>>>> --- a/drivers/input/misc/xen-kbdfront.c
>>>>> +++ b/drivers/input/misc/xen-kbdfront.c
>>>>> @@ -41,6 +41,12 @@ struct xenkbd_info {
>>>>>         char phys[32];
>>>>>     };
>>>>>     +enum { KPARAM_WIDTH, KPARAM_HEIGHT, KPARAM_CNT };
>>>>> +static int size[KPARAM_CNT] = { XENFB_WIDTH, XENFB_HEIGHT };
>>>>> +module_param_array(size, int, NULL, 0444);
>>>> is this by intention that you use 0444 here?
>>>> It means read-only, thus one cannot change these,
>>>> so what is the point of the module parameters then?
>>> You can see the settings in sysfs.
>> this is good so we can see actual width/height
>> used by the pv driver
>>> The values are settable via boot parameter.
>> but then, if one has other values set in XenStore,
>> these will/may be overridden, making it inconsistent,
>> e.g. values loaded at start as module parameters
>> (*size* array) is not going to be updated on
>> XenbusStateInitWait/XenbusStateConnected. So, we'll
>> end up with wrong parameters shown via sysfs
>> one more question is why do we need module parameters
>> if the same can be read from XenStore?
> Because up to now nobody is setting the Xenstore values. This is
> something I'm planning to do for Xen 4.10.
ah, good to know. btw, if you are about to add
width/height for the pointer device will you also add
the same for multi-touch?
>   Up to then we need a
> workaround.
>
> But you are right: The module parameters should be updated with
> the values read from Xenstore.
>
>
> Juergen