Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v7 27/34] i2c: tegra: Check errors for both positive and
 negative values
To:     Thierry Reding <thierry.reding@gmail.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>
Cc:     Jonathan Hunter <jonathanh@nvidia.com>,
        Laxman Dewangan <ldewangan@nvidia.com>,
        Wolfram Sang <wsa@the-dreams.de>,
        =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= <mirq-linux@rere.qmqm.pl>,
        linux-i2c <linux-i2c@vger.kernel.org>,
        linux-tegra@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
References: <20200908224006.25636-1-digetx@gmail.com>
 <20200908224006.25636-28-digetx@gmail.com> <20200917120955.GF3515672@ulmo>
 <CAHp75VdEoLAMvQWb1_p8ydROmY9p7KCqFGarRsgM8p8nDhyY7g@mail.gmail.com>
 <20200921112425.GK3950626@ulmo>
From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <0d18c64c-8765-a840-f963-ba6a205f0e6a@gmail.com>
Date:   Mon, 21 Sep 2020 17:13:34 +0300
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.10.0
MIME-Version: 1.0
In-Reply-To: <20200921112425.GK3950626@ulmo>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Precedence: bulk

21.09.2020 14:24, Thierry Reding пишет:
> On Thu, Sep 17, 2020 at 04:50:06PM +0300, Andy Shevchenko wrote:
>> On Thu, Sep 17, 2020 at 3:09 PM Thierry Reding <thierry.reding@gmail.com> wrote:
>>> On Wed, Sep 09, 2020 at 01:39:59AM +0300, Dmitry Osipenko wrote:
>>
>>> Why? All of these functions "return 0 on success or a negative error
>>> code on failure", don't they?
>>
>> And what is the point of having ' < 0' in all those cases?
> 
> It's explicitly checking for the documented error cases. And you'll
> occasionally have a function that can return non-zero on success.
> Testing for < 0 is the safest way to check for failure in the majority
> of cases.

If you're testing only for negative errors, then it means that you will
miss wrong positive errors, potentially setting machine on fire :) This
is not an often problem for kernel, but this is a problem that I
experienced with userspace more than one time.

Anyways, this patch also makes the errors checking consistent across the
whole driver and it makes the code look cleaner, so I'll prefer to keep
this patch as-is.