From: Jie Deng <jie.deng@intel.com>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: linux-i2c@vger.kernel.org,
virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org, wsa@kernel.org,
wsa+renesas@sang-engineering.com, mst@redhat.com, arnd@arndb.de,
jasowang@redhat.com, andriy.shevchenko@linux.intel.com,
yu1.wang@intel.com, shuo.a.liu@intel.com, conghui.chen@intel.com,
stefanha@redhat.com
Subject: Re: [PATCH v11] i2c: virtio: add a virtio i2c frontend driver
Date: Thu, 1 Jul 2021 14:10:48 +0800 [thread overview]
Message-ID: <cb35472d-f79e-f3f8-405f-35c699d897a1@intel.com> (raw)
In-Reply-To: <20210701040436.p7kega6rzeqz5tlm@vireshk-i7>
On 2021/7/1 12:04, Viresh Kumar wrote:
> On 01-07-21, 11:24, Jie Deng wrote:
>> Changes v10 -> v11
>> - Remove vi->adap.class = I2C_CLASS_DEPRECATED.
>> - Use #ifdef CONFIG_PM_SLEEP to replace the "__maybe_unused".
>> - Remove "struct mutex lock" in "struct virtio_i2c".
>> - Support zero-length request.
>> - Remove unnecessary logs.
>> - Remove vi->adap.timeout = HZ / 10, just use the default value.
>> - Use BIT(0) to define VIRTIO_I2C_FLAGS_FAIL_NEXT.
>> - Add the virtio_device index to adapter's naming mechanism.
> Thanks Jie.
>
> I hope you are going to send a fix for specification as well (for the
> zero-length request) ?
Yes. I will send that fix once this patch get merged.
>
>> diff --git a/drivers/i2c/busses/i2c-virtio.c b/drivers/i2c/busses/i2c-virtio.c
>> +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;
>> +
>> + for (i = 0; i < nr; i++) {
>> + /*
>> + * Only 7-bit mode supported for this moment. For the address format,
>> + * Please check the Virtio I2C Specification.
>> + */
>> + reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1);
>> +
>> + if (i != nr - 1)
>> + reqs[i].out_hdr.flags = cpu_to_le32(VIRTIO_I2C_FLAGS_FAIL_NEXT);
>> +
>> + outcnt = incnt = 0;
>> + sg_init_one(&out_hdr, &reqs[i].out_hdr, sizeof(reqs[i].out_hdr));
>> + sgs[outcnt++] = &out_hdr;
>> +
>> + reqs[i].buf = i2c_get_dma_safe_msg_buf(&msgs[i], 1);
>> + if (!reqs[i].buf)
>> + break;
>> +
>> + sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len);
> The len can be zero here for zero-length transfers.
>
>> +
>> + if (msgs[i].flags & I2C_M_RD)
>> + sgs[outcnt + incnt++] = &msg_buf;
>> + else
>> + sgs[outcnt++] = &msg_buf;
>> +
>> + sg_init_one(&in_hdr, &reqs[i].in_hdr, sizeof(reqs[i].in_hdr));
>> + sgs[outcnt + incnt++] = &in_hdr;
> Why are we still sending the msg_buf if the length is 0? Sending the
> buffer makes sense if you have some data to send, but otherwise it is
> just an extra sg element, which isn't required to be sent.
I think a fixed number of sgs will make things easier to develop backend.
If you prefer to parse the number of descriptors instead of using the
msg length to
distinguish the zero-length request from other requests, I'm OK to set a
limit.
if (!msgs[i].len) {
sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len);
if (msgs[i].flags & I2C_M_RD)
sgs[outcnt + incnt++] = &msg_buf;
else
sgs[outcnt++] = &msg_buf;
}
>
>> +#ifdef CONFIG_PM_SLEEP
>> +static int virtio_i2c_freeze(struct virtio_device *vdev)
>> +{
>> + virtio_i2c_del_vqs(vdev);
>> + return 0;
>> +}
>> +
>> +static int virtio_i2c_restore(struct virtio_device *vdev)
>> +{
>> + return virtio_i2c_setup_vqs(vdev->priv);
>> +}
>> +#endif
>> +
>> +static struct virtio_driver virtio_i2c_driver = {
>> + .id_table = id_table,
>> + .probe = virtio_i2c_probe,
>> + .remove = virtio_i2c_remove,
>> + .driver = {
>> + .name = "i2c_virtio",
>> + },
>> +#ifdef CONFIG_PM_SLEEP
> You could avoid this pair of ifdef by creating dummy versions of below
> routines for !CONFIG_PM_SLEEP case. Up to you.
Thank you. I'd like to keep the same.
next prev parent reply other threads:[~2021-07-01 6:11 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-01 3:24 [PATCH v11] i2c: virtio: add a virtio i2c frontend driver Jie Deng
2021-07-01 4:04 ` Viresh Kumar
2021-07-01 6:10 ` Jie Deng [this message]
2021-07-01 6:18 ` Viresh Kumar
2021-07-02 3:36 ` Jie Deng
2021-07-02 4:56 ` Viresh Kumar
2021-07-01 19:24 ` Wolfram Sang
2021-07-02 4:55 ` Viresh Kumar
2021-07-02 6:22 ` Wolfram Sang
2021-07-02 6:52 ` Jie Deng
2021-07-02 6:56 ` Viresh Kumar
2021-07-02 7:11 ` Wolfram Sang
2021-07-02 7:15 ` Jie Deng
2021-07-02 7:21 ` Viresh Kumar
2021-07-02 7:36 ` Wolfram Sang
2021-07-01 8:50 ` kernel test robot
2021-07-01 10:00 ` kernel test robot
2021-07-02 3:12 ` Jie Deng
2021-07-02 6:38 ` [kbuild-all] " Rong Chen
2021-07-01 10:45 ` Andy Shevchenko
2021-07-02 1:05 ` Jie Deng
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