linux-kernel - Re: [PATCH 2/2] i2c: dln2: simplify return flow for dln2_i2c

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Date:	Wed, 12 Nov 2014 11:39:43 +0100
From:	Johan Hovold <johan@...nel.org>
To:	Julia Lawall <julia.lawall@...6.fr>
Cc:	Octavian Purdila <octavian.purdila@...el.com>,
	Johan Hovold <johan@...nel.org>,
	Lee Jones <lee.jones@...aro.org>,
	Laurentiu Palcu <laurentiu.palcu@...el.com>,
	Wolfram Sang <wsa@...-dreams.de>,
	linux-i2c <linux-i2c@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] i2c: dln2: simplify return flow for dln2_i2c_enable

On Tue, Nov 11, 2014 at 05:20:37PM +0100, Julia Lawall wrote:
> On Tue, 11 Nov 2014, Octavian Purdila wrote:
> 
> > On Tue, Nov 11, 2014 at 2:26 PM, Johan Hovold <johan@...nel.org> wrote:
> > > On Tue, Nov 11, 2014 at 02:20:57PM +0200, Octavian Purdila wrote:
> > >> This fixes the following kbuild test robot warning:
> > >>
> > >> >> drivers/i2c/busses/i2c-dln2.c:70:1-4: WARNING: end returns can be simplified if negative or 0 value
> > >>
> > >> Reported-by: kbuild test robot <fengguang.wu@...el.com>
> > >> Reported-by: Julia Lawall <julia.lawall@...6.fr>
> > >>
> > >> Signed-off-by: Octavian Purdila <octavian.purdila@...el.com>
> > >> ---
> > >>  drivers/i2c/busses/i2c-dln2.c | 7 +------
> > >>  1 file changed, 1 insertion(+), 6 deletions(-)
> > >>
> > >> diff --git a/drivers/i2c/busses/i2c-dln2.c b/drivers/i2c/busses/i2c-dln2.c
> > >> index 010a5fa..b3fb86a 100644
> > >> --- a/drivers/i2c/busses/i2c-dln2.c
> > >> +++ b/drivers/i2c/busses/i2c-dln2.c
> > >> @@ -54,7 +54,6 @@ struct dln2_i2c {
> > >>
> > >>  static int dln2_i2c_enable(struct dln2_i2c *dln2, bool enable)
> > >>  {
> > >> -     int ret;
> > >>       u16 cmd;
> > >>       struct {
> > >>               u8 port;
> > >> @@ -67,11 +66,7 @@ static int dln2_i2c_enable(struct dln2_i2c *dln2, bool enable)
> > >>       else
> > >>               cmd = DLN2_I2C_DISABLE;
> > >>
> > >> -     ret = dln2_transfer_tx(dln2->pdev, cmd, &tx, sizeof(tx));
> > >> -     if (ret < 0)
> > >> -             return ret;
> > >> -
> > >> -     return 0;
> > >> +     return dln2_transfer_tx(dln2->pdev, cmd, &tx, sizeof(tx));
> > >
> > > This looks like a bogus warning. It's not generally equivalent (ret > 0)
> > > and is not mandated by any style guide lines.
> > >
> > 
> > In this particular it should be equivalent (with the previous fix) and
> > it saves 5 lines, so I think its worth it.
> 
> It's marked as a warning because it is not generally equivalent.  But 
> there may be many cases where it is equivalent, and in this case the 
> documentation for the function said that it should have been.  So I think 
> that the warning is useful.

I still think "warning" is too strong, "hint" would perhaps be more
appropriate, if at all needed.

Sure we can save four lines of code this way, but we also hide the
return value of the function so that instead of just looking at the
function itself I now have to look at the documentation of the final
function call (and hope it is up to date) to figure out the return
value (e.g. it may return the number of bytes transfered on success).

I also believe using a temporary is preferred for purely aesthetic
reasons in case the final function call has enough parameters that it
needs to use continuation lines.

Johan
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