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

[Viresh Kumar]

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 ?

What about this on top of your patch ?

---
 drivers/i2c/busses/i2c-virtio.c | 31 +++++++++++--------------------
 include/uapi/linux/virtio_i2c.h |  3 +--
 2 files changed, 12 insertions(+), 22 deletions(-)

diff --git a/drivers/i2c/busses/i2c-virtio.c b/drivers/i2c/busses/i2c-virtio.c
index 8c8bc9545418..e71ab1d2c83f 100644
--- a/drivers/i2c/busses/i2c-virtio.c
+++ b/drivers/i2c/busses/i2c-virtio.c
@@ -67,14 +67,13 @@ static int virtio_i2c_send_reqs(struct virtqueue *vq,
                if (!buf)
                        break;
 
+               reqs[i].buf = buf;
+               sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len);
+
                if (msgs[i].flags & I2C_M_RD) {
-                       reqs[i].read_buf = buf;
-                       sg_init_one(&msg_buf, reqs[i].read_buf, msgs[i].len);
                        sgs[outcnt + incnt++] = &msg_buf;
                } else {
-                       reqs[i].write_buf = buf;
-                       memcpy(reqs[i].write_buf, msgs[i].buf, msgs[i].len);
-                       sg_init_one(&msg_buf, reqs[i].write_buf, msgs[i].len);
+                       memcpy(reqs[i].buf, msgs[i].buf, msgs[i].len);
                        sgs[outcnt++] = &msg_buf;
                }
 
@@ -84,13 +83,8 @@ static int virtio_i2c_send_reqs(struct virtqueue *vq,
                err = virtqueue_add_sgs(vq, sgs, outcnt, incnt, &reqs[i], 
GFP_KERNEL);
                if (err < 0) {
                        pr_err("failed to add msg[%d] to virtqueue.\n", i);
-                       if (msgs[i].flags & I2C_M_RD) {
-                               kfree(reqs[i].read_buf);
-                               reqs[i].read_buf = NULL;
-                       } else {
-                               kfree(reqs[i].write_buf);
-                               reqs[i].write_buf = NULL;
-                       }
+                       kfree(reqs[i].buf);
+                       reqs[i].buf = NULL;
                        break;
                }
        }
@@ -118,14 +112,11 @@ static int virtio_i2c_complete_reqs(struct virtqueue *vq,
                        break;
                }
 
-               if (msgs[i].flags & I2C_M_RD) {
-                       memcpy(msgs[i].buf, req->read_buf, msgs[i].len);
-                       kfree(req->read_buf);
-                       req->read_buf = NULL;
-               } else {
-                       kfree(req->write_buf);
-                       req->write_buf = NULL;
-               }
+               if (msgs[i].flags & I2C_M_RD)
+                       memcpy(msgs[i].buf, req->buf, msgs[i].len);
+
+               kfree(req->buf);
+               req->buf = NULL;
        }
 
        return i;
diff --git a/include/uapi/linux/virtio_i2c.h b/include/uapi/linux/virtio_i2c.h
index 92febf0c527e..61f0086ac75b 100644
--- a/include/uapi/linux/virtio_i2c.h
+++ b/include/uapi/linux/virtio_i2c.h
@@ -48,8 +48,7 @@ struct virtio_i2c_in_hdr {
  */
 struct virtio_i2c_req {
        struct virtio_i2c_out_hdr out_hdr;
-       u8 *write_buf;
-       u8 *read_buf;
+       u8 *buf;
        struct virtio_i2c_in_hdr in_hdr;
 };
 
-- 
viresh