linux-kernel - Re: [PATCH 2/3] Input: of_touchscreen - fix setting max values on X/Y axis

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <559F832E.9080205@ti.com>
Date:	Fri, 10 Jul 2015 11:32:46 +0300
From:	Roger Quadros <rogerq@...com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:	<linux-input@...r.kernel.org>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Sebastian Reichel <sre@...nel.org>,
	Pavel Machek <pavel@....cz>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] Input: of_touchscreen - fix setting max values on
 X/Y axis

On 09/07/15 21:16, Dmitry Torokhov wrote:
> On Thu, Jul 09, 2015 at 11:32:11AM +0300, Roger Quadros wrote:
>> Dmitry,
>>
>> On 08/07/15 18:08, Dmitry Torokhov wrote:
>>> On Wed, Jul 08, 2015 at 10:59:04AM +0300, Roger Quadros wrote:
>>>> Dmitry,
>>>>
>>>> On 07/07/15 19:25, Dmitry Torokhov wrote:
>>>>> Hi Roger,
>>>>>
>>>>> On Tue, Jul 07, 2015 at 12:37:31PM +0300, Roger Quadros wrote:
>>>>>> Hi Dmitry,
>>>>>>
>>>>>> On 07/07/15 03:27, Dmitry Torokhov wrote:
>>>>>>> The binding specification says that "touchscreen-size-x" and "-y" specify
>>>>>>> horizontal and vertical resolution of the touchscreen and therefore maximum
>>>>>>> absolute coordinates should be reduced by 1 since we are starting with 0.
>>>>>>>
>>>>>>> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
>>>>>>> ---
>>>>>>>  drivers/input/touchscreen/of_touchscreen.c | 10 ++++++----
>>>>>>>  1 file changed, 6 insertions(+), 4 deletions(-)
>>>>>>>
>>>>>>> diff --git a/drivers/input/touchscreen/of_touchscreen.c b/drivers/input/touchscreen/of_touchscreen.c
>>>>>>> index 759cf4b..50bc0f2 100644
>>>>>>> --- a/drivers/input/touchscreen/of_touchscreen.c
>>>>>>> +++ b/drivers/input/touchscreen/of_touchscreen.c
>>>>>>> @@ -71,23 +71,25 @@ void touchscreen_parse_of_params(struct input_dev *dev, bool multitouch)
>>>>>>>
>>>>>>>  	axis = multitouch ? ABS_MT_POSITION_X : ABS_X;
>>>>>>>  	data_present = touchscreen_get_prop_u32(np, "touchscreen-size-x",
>>>>>>> -						input_abs_get_max(dev, axis),
>>>>>>> +						input_abs_get_max(dev,
>>>>>>> +								  axis) + 1,
>>>>>>
>>>>>> Why do we need to pass default_value to touchscreen_get_prop_u32()?
>>>>>> If the property doesn't exist we are not updating the parameter
>>>>>> anyway right?
>>>>>
>>>>> The binding can specify max, fuzz, both, or neither. If only one is
>>>>> specified we do not want to "undo" whatever the driver did (for example
>>>>
>>>> why not? At least that is not what touchscreen_parse_properties() does.
>>>> It will update the touchscreen params if any one of the DT property
>>>> is present.
>>>
>>> Yes, but while keeping the old properties (max, fuzz) intact if they
>>> have not been specified in dts. That is why we are passing default value
>>> to touchscreen_get_prop_u32.
>>>
>>>>
>>>>> tsc2005 sets up the default maximums before trying to parse OF), so we
>>>>> fetch the current value and pass it on as default one.
>>>>
>>>> This is what would happen in tsc2005 case
>>>>
>>>> -driver first sets ABS_X_max to 0xfff and ABS_Y_max to 0xfff.
>>>> -calls touchscreen_parse_properties()
>>>> -which calls touchscreen_get_prop_u32(dev, "touchscreen-size-x",
>>>> 0xfff+1, &maximum)
>>>> -if DT properties are missing, touchscreen_get_prop_u32() changes
>>>> ABS_X_max to 0x1000 and returns false.
>>>> - as data_present is false we don't do a -1 and so we have ABS_X_max
>>>> changed to 0x1000.
>>>
>>> If data_present is false we do not call input_set_abs_params() at all
>>> ans so nothing changes in input device settings.  Now, if fuzz would be
>>
>> You are right. I missed the fact that we don't call input_set_abs_params()
>> in data_present is false case hence my confusion.
>>
>>> set up (but size was not) we would be calling input_set_abs_params(),
>>> but given that we subtract 1 from maximum returned by
>>> touchscreen_get_prop_u32() we'd be setting input_set_abs_params(input,
>>> ABS_X, 0, 0x1000 - 1, fuzz) thus preserving 0xfff value set by the
>>> driver.
>>>
>>>>
>>>> This doesn't look right.
>>>>
>>>> So IMO default_value parameter can be removed from
>>>> touchscreen_get_prop_u32() to make things simpler.
>>>>
>>>> If the property doesn't exist it will not change *value and return false.
>>>
>>> But it will change if one of the properties set. For example, if you set
>>> fuzz but not size.
>>
>> Yes. Thanks for explaining :).
> 
> No problem. Can I put you down as "reviewed-by" on the of_touchscreen
> changes then?

Yes please.
For all 3 patches.

Reviewed-by: Roger Quadros <rogerq@...com>

cheers,
-roger
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/