On 09-07-21, 10:25, Jie Deng wrote: > Add an I2C bus driver for virtio para-virtualization. > > The controller can be emulated by the backend driver in > any device model software by following the virtio protocol. > > The device specification can be found on > https://lists.oasis-open.org/archives/virtio-comment/202101/msg00008.html. > > By following the specification, people may implement different > backend drivers to emulate different controllers according to > their needs. > > Co-developed-by: Conghui Chen <conghui.chen@xxxxxxxxx> > Signed-off-by: Conghui Chen <conghui.chen@xxxxxxxxx> > Signed-off-by: Jie Deng <jie.deng@xxxxxxxxx> > --- > Changes v13 -> v14 > - Put the headers in virtio_i2c.h in alphabetical order. > - Dropped I2C_FUNC_SMBUS_QUICK support. > - Dropped few unnecessary variables and checks. > - Use "num" everywhere instead of num or nr, to be consistent. > - Added few comments which make the design more clear. Thanks a lot for following this up so far :) > +static int virtio_i2c_prepare_reqs(struct virtqueue *vq, > + struct virtio_i2c_req *reqs, > + struct i2c_msg *msgs, int num) > +{ > + struct scatterlist *sgs[3], out_hdr, msg_buf, in_hdr; > + int i; > + > + for (i = 0; i < num; i++) { > + int outcnt = 0, incnt = 0; > + > + /* > + * We don't support 0 length messages and so masked out > + * I2C_FUNC_SMBUS_QUICK in virtio_i2c_func(). > + */ > + if (!msgs[i].len) > + break; > + > + /* > + * Only 7-bit mode supported for this moment. For the address > + * format, Please check the Virtio I2C Specification. > + */ > + reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1); > + > + if (i != num - 1) > + reqs[i].out_hdr.flags = cpu_to_le32(VIRTIO_I2C_FLAGS_FAIL_NEXT); > + > + sg_init_one(&out_hdr, &reqs[i].out_hdr, sizeof(reqs[i].out_hdr)); > + sgs[outcnt++] = &out_hdr; > + > + 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; > + > + sg_init_one(&in_hdr, &reqs[i].in_hdr, sizeof(reqs[i].in_hdr)); > + sgs[outcnt + incnt++] = &in_hdr; > + > + if (virtqueue_add_sgs(vq, sgs, outcnt, incnt, &reqs[i], GFP_KERNEL)) { > + i2c_put_dma_safe_msg_buf(reqs[i].buf, &msgs[i], false); > + break; > + } > + } > + > + return i; > +} Wolfram, in case you wonder why we don't error out early as discussed earlier, then ... > +static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, > + int num) > +{ ... > + /* > + * For the case where count < num, i.e. we weren't able to queue all the > + * msgs, ideally we should abort right away and return early, but some > + * of the messages are already sent to the remote I2C controller and the > + * virtqueue will be left in undefined state in that case. We kick the > + * remote here to clear the virtqueue, so we can try another set of > + * messages later on. > + */ ... here is the reasoning for that. Please see if you can still get it merged into 5.14-rc1/2. Thanks. Reviewed-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx> Tested-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx> -- viresh _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
