[v2] chardev: Improve @docstring and clarify qemu_chr_write() uses

[PATCH v2 9/9] hw/char: Simplify when qemu_chr_fe_write() could not write

Posted by Philippe Mathieu-Daudé 3 weeks, 2 days ago

If no chars were written, avoid to access the FIFO.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 hw/char/cadence_uart.c | 2 +-
 hw/char/ibex_uart.c    | 2 +-
 hw/char/sifive_uart.c  | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/hw/char/cadence_uart.c b/hw/char/cadence_uart.c
index 0dfa356b6d0..8908ebbe34a 100644
--- a/hw/char/cadence_uart.c
+++ b/hw/char/cadence_uart.c
@@ -316,7 +316,7 @@ static gboolean cadence_uart_xmit(void *do_not_use, GIOCondition cond,
 
     ret = qemu_chr_fe_write(&s->chr, s->tx_fifo, s->tx_count);
 
-    if (ret >= 0) {
+    if (ret > 0) {
         s->tx_count -= ret;
         memmove(s->tx_fifo, s->tx_fifo + ret, s->tx_count);
     }
diff --git a/hw/char/ibex_uart.c b/hw/char/ibex_uart.c
index d6f0d18c777..b7843c7a741 100644
--- a/hw/char/ibex_uart.c
+++ b/hw/char/ibex_uart.c
@@ -161,7 +161,7 @@ static gboolean ibex_uart_xmit(void *do_not_use, GIOCondition cond,
 
     ret = qemu_chr_fe_write(&s->chr, s->tx_fifo, s->tx_level);
 
-    if (ret >= 0) {
+    if (ret > 0) {
         s->tx_level -= ret;
         memmove(s->tx_fifo, s->tx_fifo + ret, s->tx_level);
     }
diff --git a/hw/char/sifive_uart.c b/hw/char/sifive_uart.c
index e7357d585a1..e5b381425a9 100644
--- a/hw/char/sifive_uart.c
+++ b/hw/char/sifive_uart.c
@@ -83,7 +83,7 @@ static gboolean sifive_uart_xmit(void *do_not_use, GIOCondition cond,
                                    fifo8_num_used(&s->tx_fifo), &numptr);
     ret = qemu_chr_fe_write(&s->chr, characters, numptr);
 
-    if (ret >= 0) {
+    if (ret > 0) {
         /* We wrote the data, actually pop the fifo */
         fifo8_pop_bufptr(&s->tx_fifo, ret, NULL);
     }
-- 
2.51.0

Re: [PATCH v2 9/9] hw/char: Simplify when qemu_chr_fe_write() could not write

Posted by Marc-André Lureau 2 weeks, 3 days ago

On Wed, Oct 22, 2025 at 7:10 PM Philippe Mathieu-Daudé
<philmd@linaro.org> wrote:
>
> If no chars were written, avoid to access the FIFO.
>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

> ---
>  hw/char/cadence_uart.c | 2 +-
>  hw/char/ibex_uart.c    | 2 +-
>  hw/char/sifive_uart.c  | 2 +-
>  3 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/hw/char/cadence_uart.c b/hw/char/cadence_uart.c
> index 0dfa356b6d0..8908ebbe34a 100644
> --- a/hw/char/cadence_uart.c
> +++ b/hw/char/cadence_uart.c
> @@ -316,7 +316,7 @@ static gboolean cadence_uart_xmit(void *do_not_use, GIOCondition cond,
>
>      ret = qemu_chr_fe_write(&s->chr, s->tx_fifo, s->tx_count);
>
> -    if (ret >= 0) {
> +    if (ret > 0) {
>          s->tx_count -= ret;
>          memmove(s->tx_fifo, s->tx_fifo + ret, s->tx_count);
>      }
> diff --git a/hw/char/ibex_uart.c b/hw/char/ibex_uart.c
> index d6f0d18c777..b7843c7a741 100644
> --- a/hw/char/ibex_uart.c
> +++ b/hw/char/ibex_uart.c
> @@ -161,7 +161,7 @@ static gboolean ibex_uart_xmit(void *do_not_use, GIOCondition cond,
>
>      ret = qemu_chr_fe_write(&s->chr, s->tx_fifo, s->tx_level);
>
> -    if (ret >= 0) {
> +    if (ret > 0) {
>          s->tx_level -= ret;
>          memmove(s->tx_fifo, s->tx_fifo + ret, s->tx_level);
>      }
> diff --git a/hw/char/sifive_uart.c b/hw/char/sifive_uart.c
> index e7357d585a1..e5b381425a9 100644
> --- a/hw/char/sifive_uart.c
> +++ b/hw/char/sifive_uart.c
> @@ -83,7 +83,7 @@ static gboolean sifive_uart_xmit(void *do_not_use, GIOCondition cond,
>                                     fifo8_num_used(&s->tx_fifo), &numptr);
>      ret = qemu_chr_fe_write(&s->chr, characters, numptr);
>
> -    if (ret >= 0) {
> +    if (ret > 0) {
>          /* We wrote the data, actually pop the fifo */
>          fifo8_pop_bufptr(&s->tx_fifo, ret, NULL);
>      }
> --
> 2.51.0
>
>


-- 
Marc-André Lureau