On 2021/7/1 14:18, Viresh Kumar wrote:
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.
OK. Let's add the following two lines to make sure that msg_buf is only
sent when the msgs len is not zero. And backend judges whether it is
a zero-length request by checking the number of elements received.
+ if (msgs[i].len) {
reqs[i].buf = i2c_get_dma_safe_msg_buf(&msgs[i], 1);
if (!reqs[i].buf)
break;
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;
+}
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