[PULL 1/2] hw/sd/ssi-sd: Return noise (dummy byte) when no card connected

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

Commit 1585ab9f1ba ("hw/sd/sdcard: Fill SPI response bits in card
code") exposed a bug in the SPI adapter: if no SD card is plugged,
we are returning "there is a card with an error". This is wrong,
we shouldn't return any particular packet response, but the noise
shifted on the MISO line. Return the dummy byte, otherwise we get:

  qemu-system-riscv64: ../hw/sd/ssi-sd.c:160: ssi_sd_transfer: Assertion `s->arglen > 0' failed.

Reported-by: Guenter Roeck <linux@roeck-us.net>
Fixes: 775616c3ae8 ("Partial SD card SPI mode support")
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Gustavo Romero <gustavo.romero@linaro.org>
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20250812140415.70153-2-philmd@linaro.org>
---
 hw/sd/ssi-sd.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/hw/sd/ssi-sd.c b/hw/sd/ssi-sd.c
index 594dead19ee..3aacbd03871 100644
--- a/hw/sd/ssi-sd.c
+++ b/hw/sd/ssi-sd.c
@@ -89,6 +89,10 @@ static uint32_t ssi_sd_transfer(SSIPeripheral *dev, uint32_t val)
     SDRequest request;
     uint8_t longresp[5];
 
+    if (!sdbus_get_inserted(&s->sdbus)) {
+        return SSI_DUMMY;
+    }
+
     /*
      * Special case: allow CMD12 (STOP TRANSMISSION) while reading data.
      *
-- 
2.49.0