[PATCH for-6.2] hw/misc/sifive_u_otp: Use IF_PFLASH for the OTP device instead of IF_NONE

[Thomas Huth <thuth@redhat.com>]

Configuring a drive with "if=none" is meant for creation of a backend
only, it should not get automatically assigned to a device frontend.
Use "if=pflash" for the One-Time-Programmable device instead (like
it is e.g. also done for the efuse device in hw/arm/xlnx-zcu102.c).

Since the old way of configuring the device has already been published
with the previous QEMU versions, we cannot remove this immediately, but
have to deprecate it and support it for at least two more releases.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 docs/about/deprecated.rst | 6 ++++++
 hw/misc/sifive_u_otp.c    | 9 ++++++++-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
index c03fcf951f..ff7488cb63 100644
--- a/docs/about/deprecated.rst
+++ b/docs/about/deprecated.rst
@@ -192,6 +192,12 @@ as short-form boolean values, and passed to plugins as ``arg_name=on``.
 However, short-form booleans are deprecated and full explicit ``arg_name=on``
 form is preferred.
 
+``-drive if=none`` for the sifive_u OTP device (since 6.2)
+''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
+
+Using ``-drive if=none`` to configure the OTP device of the sifive_u
+RISC-V machine is deprecated. Use ``-drive if=pflash`` instead.
+
 
 QEMU Machine Protocol (QMP) commands
 ------------------------------------
diff --git a/hw/misc/sifive_u_otp.c b/hw/misc/sifive_u_otp.c
index 18aa0bd55d..cf6098ff2c 100644
--- a/hw/misc/sifive_u_otp.c
+++ b/hw/misc/sifive_u_otp.c
@@ -209,7 +209,14 @@ static void sifive_u_otp_realize(DeviceState *dev, Error **errp)
                           TYPE_SIFIVE_U_OTP, SIFIVE_U_OTP_REG_SIZE);
     sysbus_init_mmio(SYS_BUS_DEVICE(dev), &s->mmio);
 
-    dinfo = drive_get_next(IF_NONE);
+    dinfo = drive_get_next(IF_PFLASH);
+    if (!dinfo) {
+        dinfo = drive_get_next(IF_NONE);
+        if (dinfo) {
+            warn_report("using \"-drive if=none\" for the OTP is deprecated, "
+                        "use \"-drive if=pflash\" instead.");
+        }
+    }
     if (dinfo) {
         int ret;
         uint64_t perm;
-- 
2.27.0