linux-kernel - Re: [PATCH 13/13] drivers/media/tuners/e4000.c: use macros for i2c

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Date:	Sun, 07 Oct 2012 19:13:24 +0200
From:	walter harms <wharms@....de>
To:	Julia Lawall <julia.lawall@...6.fr>
CC:	Antti Palosaari <crope@....fi>, kernel-janitors@...r.kernel.org,
	rmallon@...il.com, shubhrajyoti@...com,
	Mauro Carvalho Chehab <mchehab@...radead.org>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 13/13] drivers/media/tuners/e4000.c: use macros for i2c_msg
 initialization



Am 07.10.2012 18:44, schrieb Julia Lawall:
> On Sun, 7 Oct 2012, walter harms wrote:
> 
>>
>>
>> Am 07.10.2012 17:38, schrieb Julia Lawall:
>>> From: Julia Lawall <Julia.Lawall@...6.fr>
>>>
>>> Introduce use of I2c_MSG_READ/WRITE/OP, for readability.
>>>
>>> In the second i2c_msg structure, a length expressed as an explicit
>>> constant
>>> is also re-expressed as the size of the buffer, reg.
>>>
>>> A simplified version of the semantic patch that makes this change is as
>>> follows: (http://coccinelle.lip6.fr/)
>>>
>>> // <smpl>
>>> @@
>>> expression a,b,c;
>>> identifier x;
>>> @@
>>>
>>> struct i2c_msg x =
>>> - {.addr = a, .buf = b, .len = c, .flags = I2C_M_RD}
>>> + I2C_MSG_READ(a,b,c)
>>>  ;
>>>
>>> @@
>>> expression a,b,c;
>>> identifier x;
>>> @@
>>>
>>> struct i2c_msg x =
>>> - {.addr = a, .buf = b, .len = c, .flags = 0}
>>> + I2C_MSG_WRITE(a,b,c)
>>>  ;
>>>
>>> @@
>>> expression a,b,c,d;
>>> identifier x;
>>> @@
>>>
>>> struct i2c_msg x =
>>> - {.addr = a, .buf = b, .len = c, .flags = d}
>>> + I2C_MSG_OP(a,b,c,d)
>>>  ;
>>> // </smpl>
>>>
>>> Signed-off-by: Julia Lawall <Julia.Lawall@...6.fr>
>>>
>>> ---
>>>  drivers/media/tuners/e4000.c |   20 +++-----------------
>>>  1 file changed, 3 insertions(+), 17 deletions(-)
>>>
>>> diff --git a/drivers/media/tuners/e4000.c b/drivers/media/tuners/e4000.c
>>> index 1b33ed3..8f182fc 100644
>>> --- a/drivers/media/tuners/e4000.c
>>> +++ b/drivers/media/tuners/e4000.c
>>> @@ -26,12 +26,7 @@ static int e4000_wr_regs(struct e4000_priv *priv,
>>> u8 reg, u8 *val, int len)
>>>      int ret;
>>>      u8 buf[1 + len];
>>>      struct i2c_msg msg[1] = {
>>> -        {
>>> -            .addr = priv->cfg->i2c_addr,
>>> -            .flags = 0,
>>> -            .len = sizeof(buf),
>>> -            .buf = buf,
>>> -        }
>>> +        I2C_MSG_WRITE(priv->cfg->i2c_addr, buf, sizeof(buf))
>>>      };
>>>
>>
>> Any reason why struct i2c_msg is an array ?
> 
> I assumed that it looked more harmonious with the other uses of
> i2c_transfer, which takes as arguments an array and the number of elements.
> 
> But there are some files that instead use i2c_transfer(priv->i2c, &msg, 1).
> I can change them all to do that if that is preferred.  But maybe I will
> wait a little bit to see if there are other issues to address at the
> same time.
> 
> thanks,
> julia
> 

Hi Julia,
please be aware i am not the maintainer only a distant watcher :)

do you really thing that a macro is appropriate here ? I feel uneasy about it
but i can not offer an other solution.

nothing to worry about,
just my 2 cents.

re,
 wh


>>
>> re,
>> wh
>>
>>>      buf[0] = reg;
>>> @@ -54,17 +49,8 @@ static int e4000_rd_regs(struct e4000_priv *priv,
>>> u8 reg, u8 *val, int len)
>>>      int ret;
>>>      u8 buf[len];
>>>      struct i2c_msg msg[2] = {
>>> -        {
>>> -            .addr = priv->cfg->i2c_addr,
>>> -            .flags = 0,
>>> -            .len = 1,
>>> -            .buf = &reg,
>>> -        }, {
>>> -            .addr = priv->cfg->i2c_addr,
>>> -            .flags = I2C_M_RD,
>>> -            .len = sizeof(buf),
>>> -            .buf = buf,
>>> -        }
>>> +        I2C_MSG_WRITE(priv->cfg->i2c_addr, &reg, sizeof(reg)),
>>> +        I2C_MSG_READ(priv->cfg->i2c_addr, buf, sizeof(buf))
>>>      };
>>>
>>>      ret = i2c_transfer(priv->i2c, msg, 2);
>>>
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> 
> 
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