Re: [virtio-comment] [PATCH v5] virtio-i2c: add the device specification

[Jie Deng <jie.deng@intel.com>]

On 2020/12/23 6:31, Michael S. Tsirkin wrote:

> On Tue, Dec 22, 2020 at 12:29:09PM +0100, Cornelia Huck wrote:
> > Is there any reason why we need to infer the type of the request by
> > checking some lengths? Can't we just specify explicit flags for read
> > and write? What am I missing?
> >       
> Point is descriptors already have flags for read/write.
> If there is a read buffer and length > sizeof virtio_i2c_in_hdr then
> we know it's a read request.
> If there is a write buffer and length > sizeof virtio_i2c_out_hdr then
> we know it's a write request.
> If both then both.
>
> All this is known before buffer itself is consumed, which is nice.
>
> Putting this info in flags will duplicate info which is often
> a source of errors.
>
>     
    Sent the v6 with field written/read
    removed.
    
>       
>