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;
Date:   Tue, 29 Jun 2021 16:26:49 +0530
From:   Viresh Kumar <viresh.kumar@linaro.org>
To:     Wolfram Sang <wsa@kernel.org>, Jie Deng <jie.deng@intel.com>,
        linux-i2c@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, mst@redhat.com, jasowang@redhat.com,
        andriy.shevchenko@linux.intel.com, conghui.chen@intel.com,
        arnd@arndb.de, kblaiech@mellanox.com,
        jarkko.nikula@linux.intel.com, Sergey.Semin@baikalelectronics.ru,
        rppt@kernel.org, loic.poulain@linaro.org, tali.perry1@gmail.com,
        u.kleine-koenig@pengutronix.de, bjorn.andersson@linaro.org,
        yu1.wang@intel.com, shuo.a.liu@intel.com, stefanha@redhat.com,
        pbonzini@redhat.com
Subject: Re: [PATCH v10] i2c: virtio: add a virtio i2c frontend driver
Message-ID: <20210629105649.nt63mxtiy6u7de3g@vireshk-i7>
References: <226a8d5663b7bb6f5d06ede7701eedb18d1bafa1.1616493817.git.jie.deng@intel.com>
 <YNrw4rxihFLuqLtY@ninjato>
 <20210629101627.kwc2rszborc3kvjs@vireshk-i7>
 <YNr0uDx1fv+Gjd7m@ninjato>
 <20210629103014.nlk3mpetydc4mi6l@vireshk-i7>
 <YNr5Jf3WDTH7U5b7@ninjato>
 <YNr5ZRhT3qn+e9/m@ninjato>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <YNr5ZRhT3qn+e9/m@ninjato>
User-Agent: NeoMutt/20180716-391-311a52
Precedence: bulk

On 29-06-21, 12:43, Wolfram Sang wrote:
> 
> > From the spec:
> > 
> > The case when ``length of \field{write_buf}''=0, and at the same time,
> > ``length of \field{read_buf}''=0 doesn't make any sense.
> > 
> > I mentioned this in my first reply and to my understanding I did not get
> > a reply that this has changed meanwhile.
> > 
> 
> Also, this code as mentioned before:
> 
> > +             if (!msgs[i].len)
> > +                     break;
> 
> I hope this can extended in the future to allow zero-length messages. If
> this is impossible we need to set an adapter quirk instead.

Ahh, yeah I saw these messages but I wasn't able to relate them to the
I2C_FUNC_SMBUS_QUICK thing. My bad.

Looked at Spec, Linux driver and my backends, I don't there is
anything that breaks if we allow this. So the best thing (looking
ahead) is if Jie sends a patch for spec to be modified like this.

The case when ``length of \field{write_buf}''=0, and at the same time,
``length of \field{read_buf}''=0 is called not-a-read-write request
and result for such a request is I2C device specific.

-- 
viresh