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

[PATCH v2 6/9] chardev/char: Allow partial writes in qemu_chr_write()

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

If qemu_chr_write_buffer() returned an error, but could
write some characters, return the number of character
written. Otherwise frontends able to recover and resume
writes re-write the partial chars already written.

Cc: qemu-stable@nongnu.org
Suggested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 chardev/char.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/chardev/char.c b/chardev/char.c
index 30b21fedce4..5c8130b2435 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -189,7 +189,7 @@ int qemu_chr_write(Chardev *s, const uint8_t *buf, int len, bool write_all)
         replay_char_write_event_save(res, offset);
     }
 
-    if (res < 0) {
+    if (res < 0 && offset == 0) {
         return res;
     }
     return offset;
-- 
2.51.0

Re: [PATCH v2 6/9] chardev/char: Allow partial writes in qemu_chr_write()

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

Hi

On Wed, Oct 22, 2025 at 7:10 PM Philippe Mathieu-Daudé
<philmd@linaro.org> wrote:
>
> If qemu_chr_write_buffer() returned an error, but could
> write some characters, return the number of character
> written. Otherwise frontends able to recover and resume
> writes re-write the partial chars already written.
>
> Cc: qemu-stable@nongnu.org
> Suggested-by: Alex Bennée <alex.bennee@linaro.org>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> ---
>  chardev/char.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/chardev/char.c b/chardev/char.c
> index 30b21fedce4..5c8130b2435 100644
> --- a/chardev/char.c
> +++ b/chardev/char.c
> @@ -189,7 +189,7 @@ int qemu_chr_write(Chardev *s, const uint8_t *buf, int len, bool write_all)
>          replay_char_write_event_save(res, offset);
>      }
>
> -    if (res < 0) {
> +    if (res < 0 && offset == 0) {
>          return res;

If write_all==true, we should still return an error, I guess.


>      }
>      return offset;
> --
> 2.51.0
>
>


-- 
Marc-André Lureau