Re: [PATCH v4 5/6] virtio: blk: Fix converting the vendor id to a string

Kuan-Wei Chiu
2026-04-16T09:28:48Z

On Mon, Apr 13, 2026 at 06:22:39PM +0900, Daniel Palmer wrote:
> Currently we are trying to work out if the vendor id is from
> a virtio-mmio device and then casting a u32 to a char* and using
> it as a C-string. By chance there is usually a zero after the u32
> and it works.
>
> Since the vendor id we are trying to convert to a string is QEMU's
> just define a value for the QEMU vendor id, check if the vendor
> id matches and then use a predefined string for "QEMU".
>
> I don't think we should have been assumming all virtio-mmio vendor
> ids are printable ASCII chars in the first place so do this special
> casing just for QEMU. If the vendor id isn't QEMU print the hex
> value of it.
>
> Signed-off-by: Daniel Palmer <daniel@thingy.jp>
> Reviewed-by: Simon Glass <sjg@chromium.org>

Reviewed-by: Kuan-Wei Chiu <visitorckw@gmail.com>

Regards,
Kuan-Wei

> ---
> drivers/virtio/virtio_blk.c | 11 ++++-------
> include/virtio.h | 3 +++
> 2 files changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/virtio/virtio_blk.c b/drivers/virtio/virtio_blk.c
> index 3dd0cf36268b..e70cf6a776b2 100644
> --- a/drivers/virtio/virtio_blk.c
> +++ b/drivers/virtio/virtio_blk.c
> @@ -164,14 +164,11 @@ static int virtio_blk_bind(struct udevice *dev)
> return devnum;
> desc->devnum = devnum;
> desc->part_type = PART_TYPE_UNKNOWN;
> - /*
> - * virtio mmio transport supplies string identification for us,
> - * while pci trnasport uses a 2-byte subvendor value.
> - */
> - if (uc_priv->vendor >> 16)
> - sprintf(desc->vendor, "%s", (char *)&uc_priv->vendor);
> +
> + if (uc_priv->vendor == VIRTIO_VENDOR_QEMU)
> + strcpy(desc->vendor, "QEMU");
> else
> - sprintf(desc->vendor, "%04x", uc_priv->vendor);
> + sprintf(desc->vendor, "%08x", uc_priv->vendor);
> desc->bdev = dev;
>
> /* Indicate what driver features we support */
> diff --git a/include/virtio.h b/include/virtio.h
> index 17f894a79e31..3edf023463d7 100644
> --- a/include/virtio.h
> +++ b/include/virtio.h
> @@ -25,6 +25,9 @@
> #include <linux/bitops.h>
> #include <linux/bug.h>
> #include <linux/typecheck.h>
> +
> +#define VIRTIO_VENDOR_QEMU 0x554d4551
> +
> #define VIRTIO_ID_NET 1 /* virtio net */
> #define VIRTIO_ID_BLOCK 2 /* virtio block */
> #define VIRTIO_ID_RNG 4 /* virtio rng */
> --
> 2.51.0
>