Re: [Qemu-devel] [PATCH 3/3] hid.c: Add debug support

["Alex Bennée" <alex.bennee@linaro.org>]

Programmingkid <programmingkidx@gmail.com> writes:

> Add debug macros to the code for easier debugging.
>
> Signed-off-by: John Arbuckle <programmingkidx@gmail.com>
> ---
>  hw/input/hid.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/hw/input/hid.c b/hw/input/hid.c
> index 329a27b..42ca592 100644
> --- a/hw/input/hid.c
> +++ b/hw/input/hid.c
> @@ -37,6 +37,13 @@
>  #define RELEASED -1
>  #define PUSHED -2
>
> +/* #define DEBUG_HID_CODE */
> +#ifdef DEBUG_HID_CODE
> +    #define DEBUG_HID(fmt, ...) printf(fmt, __VA_ARGS__)
> +#else
> +    #define DEBUG_HID(fmt, ...) (void)0
> +#endif
> +

This style of debug setup is discouraged these days as its prone to
bitrot. It's better to define like this:

#define DEBUG_HID(fmt, ...) \
  if (DEBUG_HID_CODE) {     \
     printf(fmt, __VA_ARGS);\
  }

This means you get the benefit of the compiler checking your format
strings even if the code gets optimised away when DEBUG_HID_CODE isn't
defined.

>  /* Translates a QKeyCode to USB HID value */
>  static const uint8_t qcode_to_usb_hid[] = {
>      [Q_KEY_CODE_SHIFT] = USB_HID_LEFT_SHIFT,
> @@ -331,6 +338,7 @@ static void hid_keyboard_event(DeviceState *dev, QemuConsole *src,
>          return;
>      }
>      keycode = qcode_to_usb_hid[qcode];
> +    DEBUG_HID("keycode = 0x%x qcode:%d\n", keycode, qcode);
>
>      count = 2;
>      if (evt->u.key.data->down == false) { /* if key up event */
> @@ -381,6 +389,9 @@ static void hid_keyboard_process_keycode(HIDState *hs)
>      slot = hs->head & QUEUE_MASK; QUEUE_INCR(hs->head); hs->n--;
>      keycode = hs->kbd.keycodes[slot];
>
> +    DEBUG_HID("keycode:0x%x status:%s\n", keycode, (status == PUSHED ? "Pushed"
> +              : "Released"));
> +
>      /* handle Control, Option, GUI/Windows/Command, and Shift keys */
>      if (keycode >= 0xe0) {
>          process_modifier_key(status, keycode, &(hs->kbd.modifiers));


--
Alex Bennée