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

Daniel Palmer
2026-04-13T09:23:51Z

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>
---
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