Re: [PATCH] auxdisplay: lcd2s: add error handling for i2c transfers

[Andy Shevchenko]

On Tue, Mar 10, 2026 at 4:02 AM Wang Jun <1742789905@xxxxxx> wrote:
>
> The lcd2s_print() and lcd2s_gotoxy() functions currently ignore the
> return value of lcd2s_i2c_master_send(), which can fail. This can lead
> to silent data loss or incorrect cursor positioning.
>
> Add proper error checking: if the number of bytes sent does not match
> the expected length, return -EIO; otherwise propagate any error code
> from the I2C transfer.

> Also fix the missing return statement in lcd2s_gotoxy().

This is not correct. The return statement is there, the error checking is not.

...

>  static int lcd2s_print(struct charlcd *lcd, int c)
>  {
>         struct lcd2s_data *lcd2s = lcd->drvdata;
>         u8 buf[2] = { LCD2S_CMD_WRITE, c };
> +       int ret;
>
> -       lcd2s_i2c_master_send(lcd2s->i2c, buf, sizeof(buf));
> -       return 0;
> +       ret = lcd2s_i2c_master_send(lcd2s->i2c, buf, sizeof(buf));
> +       if (ret == sizeof(buf))
> +               return 0;
> +       else if (ret < 0)
> +               return ret;
> +       else
> +               return -EIO;

Drop redundant 'else':s and use the usual pattern, id est check for
errors first.

>  }
>
>  static int lcd2s_gotoxy(struct charlcd *lcd, unsigned int x, unsigned int y)
>  {
>         struct lcd2s_data *lcd2s = lcd->drvdata;
>         u8 buf[3] = { LCD2S_CMD_CUR_POS, y + 1, x + 1 };
> +       int ret;
>
> -       lcd2s_i2c_master_send(lcd2s->i2c, buf, sizeof(buf));
> -
> -       return 0;
> +       ret = lcd2s_i2c_master_send(lcd2s->i2c, buf, sizeof(buf));
> +       if (ret == sizeof(buf))
> +               return 0;
> +       else if (ret < 0)
> +               return ret;
> +       else
> +               return -EIO;
>  }

Same for above.

-- 
With Best Regards,
Andy Shevchenko