linux-kernel - Re: [PATCH v3 2/3] i2c: add support for Diolan DLN-2 USB-I2C adapter

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Message-ID: <CAE1zotJomxwAJA3aXm9MHnHd5Pg9V=K7XaptOPWkArV0jio4DQ@mail.gmail.com>
Date:	Mon, 8 Sep 2014 20:15:07 +0300
From:	Octavian Purdila <octavian.purdila@...el.com>
To:	Johan Hovold <johan@...nel.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Alexandre Courbot <gnurou@...il.com>, wsa@...-dreams.de,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Lee Jones <lee.jones@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Daniel Baluta <daniel.baluta@...el.com>,
	Laurentiu Palcu <laurentiu.palcu@...el.com>,
	linux-usb@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>,
	linux-gpio@...r.kernel.org, linux-i2c@...r.kernel.org
Subject: Re: [PATCH v3 2/3] i2c: add support for Diolan DLN-2 USB-I2C adapter

On Mon, Sep 8, 2014 at 7:30 PM, Johan Hovold <johan@...nel.org> wrote:
> On Mon, Sep 08, 2014 at 06:57:29PM +0300, Octavian Purdila wrote:
>> On Mon, Sep 8, 2014 at 5:44 PM, Johan Hovold <johan@...nel.org> wrote:
>>
>> <snip>
>>
>> Hi Johan,
>>
>> Again, thanks for the detailed review, I am addressing your review
>> comments as we speak. Some questions below.
>>
>> <snip>
>>
>> > > +     int ret, len;
>> > > +     struct tx_data {
>> > > +             u8 port;
>> > > +             u8 addr;
>> > > +             u8 mem_addr_len;
>> > > +             __le32 mem_addr;
>> > > +             __le16 buf_len;
>> > > +             u8 buf[DLN2_I2C_MAX_XFER_SIZE];
>> > > +     } __packed tx;
>> >
>> > Allocate these buffers dynamically (possibly at probe).
>> >
>>
>> I double checked this, and DLN2_I2C_MAX_XFER_SIZE should actually be <
>> 64 as the USB endpoint configuration max packet size is 64. In this
>> case, can we keep it on the stack?
>
> It's better to lift that restriction and allocate it dynamically. Using
> larger buffers (> EP size) is also more efficient.
>
>> <snip>
>>
>> > > +     int ret, buf_len, rx_len = sizeof(rx);
>> >
>> > Again, one declaration per line.
>>
>> AFAICS there are many places where declaration on the same line
>> (initialization included) are used. When did this became a coding
>> style issue?
>
> It's ugly, hurts readability, and can also obfuscate the fact that your
> function really needs to be refactored.
>
> And it's in the CodingStyle:
>
>         "To this end, use just one data declaration per line (no commas
>         for multiple data declarations)."
>

OK, I always thought that was for when declaring structures/unions.
Just one more question on this subject: is the following allowed:

int ret, len;

or should it be:

int ret;
int len;
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