The tx function of the DDC I2C slave emulation was returning 1
on all writes resulting in NACK in the I2C bus. Changing it to
0 makes the DDC I2C work fine with bit-banged I2C such as the
versatile I2C.

I guess it was not affecting whatever I2C controller this was
used with until now, but with the Versatile I2C it surely
does not work.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
 hw/i2c/i2c-ddc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/i2c/i2c-ddc.c b/hw/i2c/i2c-ddc.c
index 199dac9e41c1..bec0c91e2dd0 100644
--- a/hw/i2c/i2c-ddc.c
+++ b/hw/i2c/i2c-ddc.c
@@ -259,12 +259,12 @@ static int i2c_ddc_tx(I2CSlave *i2c, uint8_t data)
         s->reg = data;
         s->firstbyte = false;
         DPRINTF("[EDID] Written new pointer: %u\n", data);
-        return 1;
+        return 0;
     }
 
     /* Ignore all writes */
     s->reg++;
-    return 1;
+    return 0;
 }
 
 static void i2c_ddc_init(Object *obj)
-- 
2.14.3

On 02/27/2018 07:49 AM, Linus Walleij wrote:
> The tx function of the DDC I2C slave emulation was returning 1
> on all writes resulting in NACK in the I2C bus. Changing it to
> 0 makes the DDC I2C work fine with bit-banged I2C such as the
> versatile I2C.
> 
> I guess it was not affecting whatever I2C controller this was
> used with until now, but with the Versatile I2C it surely
> does not work.
> 
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

> ---
>  hw/i2c/i2c-ddc.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/i2c/i2c-ddc.c b/hw/i2c/i2c-ddc.c
> index 199dac9e41c1..bec0c91e2dd0 100644
> --- a/hw/i2c/i2c-ddc.c
> +++ b/hw/i2c/i2c-ddc.c
> @@ -259,12 +259,12 @@ static int i2c_ddc_tx(I2CSlave *i2c, uint8_t data)
>          s->reg = data;
>          s->firstbyte = false;
>          DPRINTF("[EDID] Written new pointer: %u\n", data);
> -        return 1;
> +        return 0;
>      }
>  
>      /* Ignore all writes */
>      s->reg++;
> -    return 1;
> +    return 0;
>  }
>  
>  static void i2c_ddc_init(Object *obj)
>