Re: [PATCH V2] virtio: i2c: Allow zero-length transactions

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

On 2021/8/17 18:43, Viresh Kumar wrote:
> On 17-08-21, 02:47, Michael S. Tsirkin wrote:
> > On Tue, Aug 17, 2021 at 09:23:24AM +0530, Viresh Kumar wrote:
> > > On 16-08-21, 10:45, Michael S. Tsirkin wrote:
> > > > So I wonder. What if we allow zero-length buffers in virtio? Would that
> > > > address the need?
> > OK, so yea. Let's split this up please.
> Just to make sure I understand what you asked for, we are looking for
> something on these lines ? And the kernel side will still send an 'sg'
> element and call sg_init_one(sg, NULL, 0) ?


From the perspective of specificationïI think we can allow zero-length 
buffers in virtio.

we can use the len of descriptor to see if it is a zero-length buffer.

But for a specific implementation, I don't think "NULL" can be passed to 
this API.

There is a check "BUG_ON(!virt_addr_valid(buf))" in it.