From: Peter Maydell <[email protected]> If the guest tries to read more bytes from our fake stub I2C device than we have provided, we incorrectly read one byte beyond the end of this array. Avoid this, and instead keep reporting the RXD register as containing the last byte of the "data transfer".
Cc: [email protected] Fixes: 9d68bf564ec ("arm: Stub out NRF51 TWI magnetometer/accelerometer detection") Resolves: https://gitlab.com/qemu-project/qemu/-/work_items/3408 Signed-off-by: Peter Maydell <[email protected]> Reviewed-by: Philippe Mathieu-Daudé <[email protected]> Message-ID: <[email protected]> Signed-off-by: Philippe Mathieu-Daudé <[email protected]> (cherry picked from commit a824f3531a44cbd19bcd9dd0ca48e5805c781e02) Signed-off-by: Michael Tokarev <[email protected]> diff --git a/hw/i2c/microbit_i2c.c b/hw/i2c/microbit_i2c.c index 2291d6370e..d9689b6f1a 100644 --- a/hw/i2c/microbit_i2c.c +++ b/hw/i2c/microbit_i2c.c @@ -41,8 +41,13 @@ static uint64_t microbit_i2c_read(void *opaque, hwaddr addr, unsigned int size) data = 0x01; break; case NRF51_TWI_REG_RXD: + /* + * Return the next byte from our fake data sequence. If + * the guest keeps reading the register after that, keep + * returning the same last byte value. + */ data = twi_read_sequence[s->read_idx]; - if (s->read_idx < G_N_ELEMENTS(twi_read_sequence)) { + if (s->read_idx + 1 < G_N_ELEMENTS(twi_read_sequence)) { s->read_idx++; } break; -- 2.47.3
