linux-kernel - Re: [PATCH v1] input: make use of the input_set

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Date:	Wed, 07 Jan 2015 10:41:24 +0100
From:	Olliver Schinagl <oliver@...inagl.nl>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:	Olliver Schinagl <oliver+list@...inagl.nl>,
	Wolfram Sang <wsa@...-dreams.de>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Jingoo Han <jg1.han@...sung.com>,
	"David S. Miller" <davem@...emloft.net>,
	Sam Ravnborg <sam@...nborg.org>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] input: make use of the input_set_capability helper

HEy Dmitry,

On 07-01-15 09:26, Dmitry Torokhov wrote:
> On Wed, Jan 07, 2015 at 09:19:28AM +0100, Olliver Schinagl wrote:
>> Hey Dmitry,
>>
>> On 07-01-15 08:57, Dmitry Torokhov wrote:
>>> Hi Olliver,
>>>
>>> On Wed, Jan 07, 2015 at 08:31:06AM +0100, Olliver Schinagl wrote:
>>>> From: Olliver Schinagl <oliver@...inagl.nl>
>>>>
>>>> Almost all of the speaker drivers under input manipulate the ev bits
>>>> directly, which is not needed, as there is a helper available.
>>>>
>>>> This patch makes use of the helper for the speaker drivers.
>>>>
>>>> Signed-off-by: Olliver Schinagl <oliver@...inagl.nl>
>>>> ---
>>>>   drivers/input/misc/cm109.c         | 4 ++--
>>>>   drivers/input/misc/ixp4xx-beeper.c | 5 ++---
>>>>   drivers/input/misc/m68kspkr.c      | 5 ++---
>>>>   drivers/input/misc/pcspkr.c        | 5 ++---
>>>>   drivers/input/misc/pwm-beeper.c    | 5 +----
>>>>   drivers/input/misc/sparcspkr.c     | 6 ++----
>>>>   6 files changed, 11 insertions(+), 19 deletions(-)
>>>>
>>>> diff --git a/drivers/input/misc/cm109.c b/drivers/input/misc/cm109.c
>>>> index 9365535..8e41070 100644
>>>> --- a/drivers/input/misc/cm109.c
>>>> +++ b/drivers/input/misc/cm109.c
>>>> @@ -767,10 +767,10 @@ static int cm109_usb_probe(struct usb_interface *intf,
>>>>   	input_dev->keycodesize = sizeof(unsigned char);
>>>>   	input_dev->keycodemax = ARRAY_SIZE(dev->keymap);
>>>> -	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_SND);
>>>> -	input_dev->sndbit[0] = BIT_MASK(SND_BELL) | BIT_MASK(SND_TONE);
>>>> +	input_set_capability(input_dev, EV_SND, SND_BELL | SND_TONE);
>>> No, input_set_capability() takes single event code, not bitmask. The
>>> fact that it works for these 2 values of SND events is pure coincidence
>>> (the old code wasn't much better though).
> Ah, not, it does not work at all. Instead of setting bits 1 and 2 your
> code sets bit 3 in dev->sndbit.
>
>> What do you suggest we should do then? Fix input_set_capability to
>> take bit masks? or multiline events?
>> I'm not sure why __set_bits() wouldn't work for bitmasks, could you
>> educate me?
> Call it once per event:
>
> 	input_set_capability(input_dev, EV_SND, SND_BELL);
> 	input_set_capability(input_dev, EV_SND, SND_TONE);
roger, done
>
>>>>   	/* register available key events */
>>>> +	input_dev->evbit[0] = BIT_MASK(EV_KEY);
>>> Would prefer __set_bit(EV_KEY, input_dev->evbit); here instead.
>> I only moved the EV_KEY bit from above to its appropiate place here.
> The original code was setting combination of bits; here we set single
> one and __set_bit() is cleaner IMO.
The documentation contradicts this actually, it says to use set_bit() 
first, but favors the direct writing as above as it is 'shorter in some 
cases'.

Furthermore, I'm a little confused as what the purpose of 
input_set_capability() is, if we use set_bits (or __set_bits) here. It 
appears we use set_bits here because it is manipulating several entries 
in the array (well atleast index 0) and set_input_capability() doesn't 
handle arrays? But when I look at struct input_dev, all those entries 
are arrays, including sndbit. So we only use set_input_capabilities when 
manipulating index 0 when its the only one? Feels a little strange to 
me, but probably is my lack of knowledge herin, so appologies for that.

Olliver
>
>> I can change this one (and others) to use __set_bit() for now for
>> v2?
> Yes, please.
>
> Thanks.
>

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