linux-kernel - Re: [PATCH v10] i2c: virtio: add a virtio i2c frontend driver

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Message-ID: <20210629105649.nt63mxtiy6u7de3g@vireshk-i7>
Date:   Tue, 29 Jun 2021 16:26:49 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Wolfram Sang <wsa@...nel.org>, Jie Deng <jie.deng@...el.com>,
        linux-i2c@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, mst@...hat.com, jasowang@...hat.com,
        andriy.shevchenko@...ux.intel.com, conghui.chen@...el.com,
        arnd@...db.de, kblaiech@...lanox.com,
        jarkko.nikula@...ux.intel.com, Sergey.Semin@...kalelectronics.ru,
        rppt@...nel.org, loic.poulain@...aro.org, tali.perry1@...il.com,
        u.kleine-koenig@...gutronix.de, bjorn.andersson@...aro.org,
        yu1.wang@...el.com, shuo.a.liu@...el.com, stefanha@...hat.com,
        pbonzini@...hat.com
Subject: Re: [PATCH v10] i2c: virtio: add a virtio i2c frontend driver

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