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

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Message-ID: <1e01448f-52f6-3d39-6794-d140637fdcc3@intel.com>
Date:   Tue, 2 Mar 2021 13:21:25 +0800
From:   Jie Deng <jie.deng@...el.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     linux-i2c@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, mst@...hat.com, wsa@...nel.org,
        jasowang@...hat.com, wsa+renesas@...g-engineering.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
Subject: Re: [PATCH v5] i2c: virtio: add a virtio i2c frontend driver


On 2021/3/2 12:42, Viresh Kumar wrote:
> On 01-03-21, 14:41, Jie Deng wrote:
>> +static int virtio_i2c_send_reqs(struct virtqueue *vq,
>> +				struct virtio_i2c_req *reqs,
>> +				struct i2c_msg *msgs, int nr)
>> +{
>> +	struct scatterlist *sgs[3], out_hdr, msg_buf, in_hdr;
>> +	int i, outcnt, incnt, err = 0;
>> +	u8 *buf;
>> +
>> +	for (i = 0; i < nr; i++) {
>> +		if (!msgs[i].len)
>> +			break;
>> +
>> +		reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1);
> And this won't work for 10 bit addressing right? Don't we support that
> in kernel ?
>
>  From Spec:
>
> \begin{tabular}{ |l||l|l|l|l|l|l|l|l|l|l|l|l|l|l|l|l| }
> \hline
> Bits           & 15 & 14 & 13 & 12 & 11 & 10 & 9  & 8  & 7  & 6  & 5  & 4  & 3  & 2  & 1  & 0 \\
> \hline
> 7-bit address  & 0  & 0  & 0  & 0  & 0  & 0  & 0  & 0  & A6 & A5 & A4 & A3 & A2 & A1 & A0 & 0 \\
> \hline
> 10-bit address & A7 & A6 & A5 & A4 & A3 & A2 & A1 & A0 & 1  & 1  & 1  & 1  & 0  & A9 & A8 & 0 \\
> \hline
> \end{tabular}
Currently, to make things simple, this driver only supports 7 bit mode.
It doesn't declare "I2C_FUNC_10BIT_ADDR" in the functionality.
We may add in the future according to the need.