On 2021/7/29 13:47, Viresh Kumar wrote:
On 29-07-21, 13:39, Jie Deng wrote:
Well, then can we also add a flag to mark the zero-length request.
I think it will be convenient for backend developers.
Hmm, I think that information is already present at the device since
only two elements will be present in the received request, one out
buffer and one in buffer. And since the middle (data) buffer is not
present, the device can easily know that it is a zero-length request.
I don't see a real advantage of adding a flag for this.
The number of descriptors required for a request will not be fixed.
If there is a descriptor sequence in the virtqueue, then you may need a
state machine
to parse the sequence. For example, when you have
WR RR ZR
O O I O I I O I
* WR:(write request), RR (read request), ZR (zero request), O: output
descriptor, I: input descriptor
When you encounter "O I" combination, you have to read the element after
it to distinguish
RR and ZR. Will this bring unnecessary difficulties for the backend coding ?
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