Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Content-Type: text/plain;
        charset=utf-8
Mime-Version: 1.0 (1.0)
Subject: Re: [PATCH] Staging: iio: ad7192: replaced bool in struct
From:   Matt Ranostay <matt.ranostay@konsulko.com>
In-Reply-To: <20181224095823.GA17061@himanshu-Vostro-3559>
Date:   Wed, 2 Jan 2019 13:25:27 -0800
Cc:     Amir Mahdi Ghorbanian <indigoomega021@gmail.com>, lars@metafoo.de,
        Michael.Hennerich@analog.com, jic23@kernel.org, knaack.h@gmx.de,
        pmeerw@pmeerw.net, gregkh@linuxfoundation.org,
        linux-iio@vger.kernel.org, devel@driverdev.osuosl.org,
        linux-kernel@vger.kernel.org
Content-Transfer-Encoding: quoted-printable
Message-Id: <8E720BF2-7AFC-4FFA-8FA2-5A403FD5DD1D@konsulko.com>
References: <1545434786-15220-1-git-send-email-indigoomega021@gmail.com> <20181224095823.GA17061@himanshu-Vostro-3559>
To:     Himanshu Jha <himanshujha199640@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


> On Dec 24, 2018, at 01:58, Himanshu Jha <himanshujha199640@gmail.com> wrot=
e:
>=20
>> On Fri, Dec 21, 2018 at 03:26:26PM -0800, Amir Mahdi Ghorbanian wrote:
>> Replaced bool in struct with unsigned int bitfield to conserve space and
>> more clearly define size of varibales

Important thing to note is depending on padding, alignment, and position of f=
ield it probably won=E2=80=99t save any space.

Also for internal unpacked structures it really makes little sense to save a=
 few bytes of data. Don=E2=80=99t read into that packed structures are good.=
. they usually aren=E2=80=99t :)

- Matt
>>=20
>> Signed-off-by: Amir Mahdi Ghorbanian <indigoomega021@gmail.com>
>> ---
>=20
> There was some discussion on this at Outreachy list:
> https://groups.google.com/d/msg/outreachy-kernel/xpQAl-Gn8HA/yqcQRG_qBgAJ
>=20
> I think unless you post some statistics about 'conserving' space,=20
> it is unlikely that maintainers will apply it.
>=20
> This idea was originally given by Linus and that thread of discussion=20
> is worth reading too.
>=20
>> drivers/staging/iio/adc/ad7192.h | 14 +++++++-------
>> 1 file changed, 7 insertions(+), 7 deletions(-)
>>=20
>> diff --git a/drivers/staging/iio/adc/ad7192.h b/drivers/staging/iio/adc/a=
d7192.h
>> index 7433a43..7d3e62f 100644
>> --- a/drivers/staging/iio/adc/ad7192.h
>> +++ b/drivers/staging/iio/adc/ad7192.h
>> @@ -35,13 +35,13 @@ struct ad7192_platform_data {
>>    u16        vref_mv;
>>    u8        clock_source_sel;
>>    u32        ext_clk_hz;
>> -    bool        refin2_en;
>> -    bool        rej60_en;
>> -    bool        sinc3_en;
>> -    bool        chop_en;
>> -    bool        buf_en;
>> -    bool        unipolar_en;
>> -    bool        burnout_curr_en;
>> +    unsigned int    refin2_en : 1;
>> +    unsigned int    rej60_en : 1;
>> +    unsigned int    sinc3_en : 1;
>> +    unsigned int    chop_en : 1;
>> +    unsigned int    buf_en : 1;
>> +    unsigned int    unipolar_en : 1;
>> +    unsigned int    burnout_curr_en : 1;
>> };
>>=20
>> #endif /* IIO_ADC_AD7192_H_ */
>> --=20
>> 2.7.4
>>=20
>=20
> Goodluck!
>=20
> --=20
> Himanshu Jha
> Undergraduate Student
> Department of Electronics & Communication
> Guru Tegh Bahadur Institute of Technology