linux-kernel - Re: [PATCH 3/13] drivers/media/tuners/qt1010.c: use macros for i2c

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Date:	Mon, 08 Oct 2012 16:13:52 +1100
From:	Ryan Mallon <rmallon@...il.com>
To:	Julia Lawall <julia.lawall@...6.fr>
CC:	Antti Palosaari <crope@....fi>, kernel-janitors@...r.kernel.org,
	shubhrajyoti@...com, Mauro Carvalho Chehab <mchehab@...radead.org>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/13] drivers/media/tuners/qt1010.c: use macros for i2c_msg
 initialization

On 08/10/12 16:05, Julia Lawall wrote:
> On Mon, 8 Oct 2012, Ryan Mallon wrote:
> 
>> On 08/10/12 02:38, Julia Lawall wrote:
>>> From: Julia Lawall <Julia.Lawall@...6.fr>
>>>
>>> Introduce use of I2c_MSG_READ/WRITE/OP, for readability.
>>>
>>> A length expressed as an explicit constant is also re-expressed as
>>> the size
>>> of the buffer, when this is possible.
>>>
>>> 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/qt1010.c |   10 ++++------
>>>  1 file changed, 4 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/media/tuners/qt1010.c
>>> b/drivers/media/tuners/qt1010.c
>>> index bc419f8..37ff254 100644
>>> --- a/drivers/media/tuners/qt1010.c
>>> +++ b/drivers/media/tuners/qt1010.c
>>> @@ -25,10 +25,8 @@
>>>  static int qt1010_readreg(struct qt1010_priv *priv, u8 reg, u8 *val)
>>>  {
>>>      struct i2c_msg msg[2] = {
>>> -        { .addr = priv->cfg->i2c_address,
>>> -          .flags = 0, .buf = &reg, .len = 1 },
>>> -        { .addr = priv->cfg->i2c_address,
>>> -          .flags = I2C_M_RD, .buf = val, .len = 1 },
>>> +        I2C_MSG_WRITE(priv->cfg->i2c_address, &reg, sizeof(reg)),
>>> +        I2C_MSG_READ(priv->cfg->i2c_address, val, 1),
>>
>> This is a bit inconsistent. For single length values we should either
>> consistently use sizeof(val) or 1. This has both.
> 
> val is a pointer.  It does not have size 1.

Sorry, I mean either:

	I2C_MSG_WRITE(priv->cfg->i2c_address, &reg, sizeof(reg)),
	I2C_MSG_READ(priv->cfg->i2c_address, val, sizeof(*val)),

or:

	I2C_MSG_WRITE(priv->cfg->i2c_address, &reg, 1),
	I2C_MSG_READ(priv->cfg->i2c_address, val, 1),

~Ryan

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