On 25-03-21, 17:16, Arnd Bergmann wrote:
> On Wed, Mar 24, 2021 at 8:33 AM Viresh Kumar <viresh.ku...@linaro.org> wrote:
>
> > +static uint8_t vi2c_xfer(VuDev *dev, struct i2c_msg *msg)
> > +{
> > + VuI2c *i2c = container_of(dev, VuI2c, dev.parent);
> > + struct i2c_rdwr_ioctl_data data;
> > + VI2cAdapter *adapter;
> > +
> > + adapter = vi2c_find_adapter(i2c, msg->addr);
> > + if (!adapter) {
> > + g_printerr("Failed to find adapter for address: %x\n", msg->addr);
> > + return VIRTIO_I2C_MSG_ERR;
> > + }
> > +
> > + data.nmsgs = 1;
> > + data.msgs = msg;
> > +
> > + if (ioctl(adapter->fd, I2C_RDWR, &data) < 0) {
> > + g_printerr("Failed to transfer data to address %x : %d\n",
> > msg->addr, errno);
> > + return VIRTIO_I2C_MSG_ERR;
> > + }
>
> As you found during testing, this doesn't work for host kernels
> that only implement the SMBUS protocol. Since most i2c clients
> only need simple register read/write operations, I think you should
> at least handle the common ones (and one two byte read/write)
> here to make it more useful.
I am thinking if that is what we really want to support, then
shouldn't the i2c virtio spec be updated first to support SMBUS type
transfers as well?
> > +static void vi2c_handle_ctrl(VuDev *dev, int qidx)
> > +{
> > + VuVirtq *vq = vu_get_queue(dev, qidx);
> > + struct i2c_msg msg;
> > + struct virtio_i2c_out_hdr *out_hdr;
> > + struct virtio_i2c_in_hdr *in_hdr;
> > + bool fail_next = false;
> > + size_t len, in_hdr_len;
> > +
> > + for (;;) {
> > + VuVirtqElement *elem;
> > +
> > + elem = vu_queue_pop(dev, vq, sizeof(VuVirtqElement));
> > + if (!elem) {
> > + break;
> > + }
> > +
> > + g_debug("%s: got queue (in %d, out %d)", __func__, elem->in_num,
> > + elem->out_num);
> > +
> > + /* Validate size of out header */
> > + if (elem->out_sg[0].iov_len != sizeof(*out_hdr)) {
> > + g_warning("%s: Invalid out hdr %zu : %zu\n", __func__,
> > + elem->out_sg[0].iov_len, sizeof(*out_hdr));
> > + continue;
> > + }
> > +
> > + out_hdr = elem->out_sg[0].iov_base;
> > +
> > + /* Bit 0 is reserved in virtio spec */
> > + msg.addr = out_hdr->addr >> 1;
> > +
> > + /* Read Operation */
> > + if (elem->out_num == 1 && elem->in_num == 2) {
> > + len = elem->in_sg[0].iov_len;
> > + if (!len) {
> > + g_warning("%s: Read buffer length can't be zero\n",
> > __func__);
> > + continue;
> > + }
>
>
> It looks like you are not handling endianness conversion here. As far as I
> can tell, the protocol requires little-endian data, but the code might
> run on a big-endian CPU.
>
> Jie Deng also pointed out the type differences, but actually handling
> them correctly is more important that describing them the right way.
Right, I missed that.
--
viresh
