linux-kernel - Re: [PATCH] Input: xen-kbdfront - allow better run-time configuration

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Date:   Thu, 19 Apr 2018 14:44:19 +0300
From:   Oleksandr Andrushchenko <andr2000@...il.com>
To:     Juergen Gross <jgross@...e.com>, xen-devel@...ts.xenproject.org,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        dmitry.torokhov@...il.com, lyan@...e.com,
        boris.ostrovsky@...cle.com
Cc:     andrii_chepurnyi@...m.com,
        Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
Subject: Re: [PATCH] Input: xen-kbdfront - allow better run-time configuration

On 04/19/2018 02:25 PM, Juergen Gross wrote:
> On 18/04/18 17:04, Oleksandr Andrushchenko wrote:
>> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
>>
>> It is now only possible to control if multi-touch virtual device
>> is created or not (via the corresponding XenStore entries),
>> but keyboard and pointer devices are always created.
> Why don't you want to go that route for keyboard and mouse, too?
> Or does this really make no sense?
Well, I would prefer not to touch anything outside Linux and
this driver. And these settings seem to be implementation specific.
So, this is why introduce Linux module parameters and don't extend
the kbdif protocol.
>> In some cases this is not desirable. For example, if virtual
>> keyboard device is exposed to Android then the latter won't
>> automatically show on-screen keyboard as it expects that a
>> physical keyboard device can be used for typing.
>>
>> Make it possible to configure which virtual devices are created
>> with module parameters:
>>    - no_ptr_dev=1 if no pointer device needs to be created
>>    - no_kbd_dev=1 if no keyboard device needs to be created
>> Keep old behavior by default.
>>
>> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
>> Suggested-by: Andrii Chepurnyi <andrii_chepurnyi@...m.com>
>> Tested-by: Andrii Chepurnyi <andrii_chepurnyi@...m.com>
>> ---
>>   drivers/input/misc/xen-kbdfront.c | 159 +++++++++++++++++-------------
>>   1 file changed, 92 insertions(+), 67 deletions(-)
>>
>> diff --git a/drivers/input/misc/xen-kbdfront.c b/drivers/input/misc/xen-kbdfront.c
>> index d91f3b1c5375..a3306aad40b0 100644
>> --- a/drivers/input/misc/xen-kbdfront.c
>> +++ b/drivers/input/misc/xen-kbdfront.c
>> @@ -51,6 +51,16 @@ module_param_array(ptr_size, int, NULL, 0444);
>>   MODULE_PARM_DESC(ptr_size,
>>   	"Pointing device width, height in pixels (default 800,600)");
>>   
>> +static unsigned int no_ptr_dev;
>> +module_param(no_ptr_dev, uint, 0);
> Use type invbool instead?
Hm, better bool then? invbool will require parameter name change to
something like "with_ptr_dev" which might confuse, e.g.
default was to go with pointer device, now we have with_ptr_dev
module parameter: do I now need to set it to preserve the old behavior?
The answer is no (because of invbool), but you have to dig for it.

Will bool work for you?
>> +MODULE_PARM_DESC(no_ptr_dev,
>> +	"If set then no virtual pointing device exposed to the guest");
>> +
>> +static unsigned int no_kbd_dev;
>> +module_param(no_kbd_dev, uint, 0);
> invbool?
>
>
> Juergen