Re: [Qemu-devel] [PATCH] cadence_uart: check for serial backend before using it.

[Peter Crosthwaite]

On Wed, Jul 16, 2014 at 1:18 AM,  <address@hidden> wrote:
> From: KONRAD Frederic <address@hidden>
>
> This checks that s->chr is not NULL before using it.
>
> Signed-off-by: KONRAD Frederic <address@hidden>
> ---
>  hw/char/cadence_uart.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/hw/char/cadence_uart.c b/hw/char/cadence_uart.c
> index dbbc167..a5736cb 100644
> --- a/hw/char/cadence_uart.c
> +++ b/hw/char/cadence_uart.c
> @@ -175,8 +175,10 @@ static void uart_send_breaks(UartState *s)
>  {
>      int break_enabled = 1;
>
> -    qemu_chr_fe_ioctl(s->chr, CHR_IOCTL_SERIAL_SET_BREAK,
> -                               &break_enabled);
> +    if (s->chr) {
> +        qemu_chr_fe_ioctl(s->chr, CHR_IOCTL_SERIAL_SET_BREAK,
> +                                   &break_enabled);
> +    }
>  }
>
>  static void uart_parameters_setup(UartState *s)
> @@ -227,7 +229,9 @@ static void uart_parameters_setup(UartState *s)
>
>      packet_size += ssp.data_bits + ssp.stop_bits;
>      s->char_tx_time = (get_ticks_per_sec() / ssp.speed) * packet_size;
> -    qemu_chr_fe_ioctl(s->chr, CHR_IOCTL_SERIAL_SET_PARAMS, &ssp);
> +    if (s->chr) {
> +        qemu_chr_fe_ioctl(s->chr, CHR_IOCTL_SERIAL_SET_PARAMS, &ssp);
> +    }
>  }
>
>  static int uart_can_receive(void *opaque)
> @@ -295,6 +299,7 @@ static gboolean cadence_uart_xmit(GIOChannel *chan, 
> GIOCondition cond,
>      /* instant drain the fifo when there's no back-end */
>      if (!s->chr) {
>          s->tx_count = 0;
> +        return FALSE;

Is this needed? With s->tx_count forced to 0 in the NULL dev case,
won't the next if trigger immediately and return?

300     if (!s->tx_count) {
301         return FALSE;
302     }

With this hunk dropped,

Reviewed-by: Peter Crosthwaite <address@hidden>

And recommended for 2.1.

Regards,
Peter

>      }
>
>      if (!s->tx_count) {
> @@ -375,7 +380,9 @@ static void uart_read_rx_fifo(UartState *s, uint32_t *c)
>          *c = s->rx_fifo[rx_rpos];
>          s->rx_count--;
>
> -        qemu_chr_accept_input(s->chr);
> +        if (s->chr) {
> +            qemu_chr_accept_input(s->chr);
> +        }
>      } else {
>          *c = 0;
>      }
> --
> 1.9.0
>
>