Re: [PATCH v11] i2c: virtio: add a virtio i2c frontend driver

From: Viresh Kumar
Date: Thu Jul 01 2021 - 02:18:53 EST

On 01-07-21, 14:10, Jie Deng wrote:
> I think a fixed number of sgs will make things easier to develop backend.

Yeah, but it looks awkward to send a message buffer which isn't used
at all. From protocol's point of view, it just looks wrong/buggy.

The backend can just look at the number of elements received, they
can either be 2 (in case of zero-length) transfer, or 3 (for
read/write) and any other number is invalid.

> 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.

My concern is more about the specification here first.

> 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
> > 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.