On 22-10-21, 14:51, Jie Deng wrote: > > + if (!virtio_has_feature(vdev, VIRTIO_I2C_F_ZERO_LENGTH_REQUEST)) { > > + dev_err(&vdev->dev, "Zero-length request feature is mandatory\n"); > > + return -EINVAL; > > > It might be better to return -EOPNOTSUPP ? Maybe that or one of these: #define EBADE 52 /* Invalid exchange */ #define EPROTO 71 /* Protocol error */ #define EPFNOSUPPORT 96 /* Protocol family not supported */ #define ECONNREFUSED 111 /* Connection refused */ Arnd, any suggestions ? This is about the mandatory feature not being offered by the device. -- viresh