Thanks!
There is no functionality issue. IS_VRING_DROP is only set for Rx. Line 634 is for Tx. So there is no case for line 634 to be used when IS_VRING_DROP() is TRUE.
But I'll submit a patch today to eliminate the warning.
Thanks,
Liming
> -----Original Message-----
> From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> Sent: Thursday, September 28, 2023 8:23 AM
> To: Liming Sun <limings@xxxxxxxxxx>
> Cc: platform-driver-x86@xxxxxxxxxxxxxxx
> Subject: [bug report] platform/mellanox: Add BlueField-3 support in the tmfifo
> driver
>
> Hello Liming Sun,
>
> The patch bc05ea63b394: "platform/mellanox: Add BlueField-3 support
> in the tmfifo driver" from Oct 18, 2022 (linux-next), leads to the
> following Smatch static checker warning:
>
> drivers/platform/mellanox/mlxbf-tmfifo.c:634
> mlxbf_tmfifo_rxtx_word()
> error: uninitialized symbol 'data'.
>
> drivers/platform/mellanox/mlxbf-tmfifo.c
> 592 static void mlxbf_tmfifo_rxtx_word(struct mlxbf_tmfifo_vring *vring,
> 593 struct vring_desc *desc,
> 594 bool is_rx, int len)
> 595 {
> 596 struct virtio_device *vdev = vring->vq->vdev;
> 597 struct mlxbf_tmfifo *fifo = vring->fifo;
> 598 void *addr;
> 599 u64 data;
> 600
> 601 /* Get the buffer address of this desc. */
> 602 addr = phys_to_virt(virtio64_to_cpu(vdev, desc->addr));
> 603
> 604 /* Read a word from FIFO for Rx. */
> 605 if (is_rx)
> 606 data = readq(fifo->rx.data);
> 607
> 608 if (vring->cur_len + sizeof(u64) <= len) {
> 609 /* The whole word. */
> 610 if (!IS_VRING_DROP(vring)) {
> 611 if (is_rx)
> 612 memcpy(addr + vring->cur_len, &data,
> 613 sizeof(u64));
> 614 else
> 615 memcpy(&data, addr + vring->cur_len,
> 616 sizeof(u64));
> 617 }
>
> if IS_VRING_DROP() is true then data isn't intialized.
>
> 618 vring->cur_len += sizeof(u64);
> 619 } else {
> 620 /* Leftover bytes. */
> 621 if (!IS_VRING_DROP(vring)) {
> 622 if (is_rx)
> 623 memcpy(addr + vring->cur_len, &data,
> 624 len - vring->cur_len);
> 625 else
> 626 memcpy(&data, addr + vring->cur_len,
> 627 len - vring->cur_len);
> 628 }
>
> Same here.
>
> 629 vring->cur_len = len;
> 630 }
> 631
> 632 /* Write the word into FIFO for Tx. */
> 633 if (!is_rx)
> --> 634 writeq(data, fifo->tx.data);
> ^^^^
> Unitialized if IS_VRING_DROP() is true.
>
> 635 }
>
> regards,
> dan carpenter
