Re: [PATCH v5] i2c: virtio: add a virtio i2c frontend driver

From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Jie Deng <jie.deng@intel.com>,
	linux-i2c@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org, mst@redhat.com, wsa@kernel.org,
	jasowang@redhat.com, wsa+renesas@sang-engineering.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
Subject: Re: [PATCH v5] i2c: virtio: add a virtio i2c frontend driver
Date: Mon, 1 Mar 2021 14:10:09 +0200	[thread overview]
Message-ID: <YDzZocYCA8UC1FCW@smile.fi.intel.com> (raw)
In-Reply-To: <YDzZdc9+6hEvIDS1@smile.fi.intel.com>

On Mon, Mar 01, 2021 at 02:09:25PM +0200, Andy Shevchenko wrote:
> On Mon, Mar 01, 2021 at 05:24:41PM +0530, Viresh Kumar wrote:
> > On 01-03-21, 14:41, Jie Deng wrote:
> > > +/**
> > > + * struct virtio_i2c_req - the virtio I2C request structure
> > > + * @out_hdr: the OUT header of the virtio I2C message
> > > + * @write_buf: contains one I2C segment being written to the device
> > > + * @read_buf: contains one I2C segment being read from the device
> > > + * @in_hdr: the IN header of the virtio I2C message
> > > + */
> > > +struct virtio_i2c_req {
> > > +	struct virtio_i2c_out_hdr out_hdr;
> > > +	u8 *write_buf;
> > > +	u8 *read_buf;
> > > +	struct virtio_i2c_in_hdr in_hdr;
> > > +};
> > 
> > I am not able to appreciate the use of write/read bufs here as we
> > aren't trying to read/write data in the same transaction. Why do we
> > have two bufs here as well as in specs ?
> 
> I²C and SMBus support bidirectional transfers as well. I think two buffers is
> the right thing to do.

Strictly speaking "half duplex".

-- 
With Best Regards,
Andy Shevchenko