Re: [Qemu-devel] [PATCH] usb: Support compilation without poll.h

[Gerd Hoffmann <kraxel@redhat.com>]

On Mi, 2016-03-16 at 21:22 +0100, Stefan Weil wrote:
> This is a hack to support compilation with Mingw-w64 which provides
> a libusb-1.0 package, but no poll.h.
> 
> Signed-off-by: Stefan Weil <sw@weilnetz.de>
> ---
> 
> I did not test whether this USB host code works on Windows,
> but at least it compiles with this hack.
> 
> Suggestions for a better fix are welcome.
> 
> Regards,
> Stefan
> 
>  hw/usb/host-libusb.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/hw/usb/host-libusb.c b/hw/usb/host-libusb.c
> index 5e7ec45..139028e 100644
> --- a/hw/usb/host-libusb.c
> +++ b/hw/usb/host-libusb.c
> @@ -34,7 +34,9 @@
>   */
>  
>  #include "qemu/osdep.h"
> +#ifdef CONFIG_PPOLL
>  #include <poll.h>
> +#endif
>  #include <libusb.h>
>  
>  #include "qemu-common.h"
> @@ -203,18 +205,24 @@ static const char *err_names[] = {
>  static libusb_context *ctx;
>  static uint32_t loglevel;
>  
> +#ifdef CONFIG_PPOLL
>  static void usb_host_handle_fd(void *opaque)
>  {
>      struct timeval tv = { 0, 0 };
>      libusb_handle_events_timeout(ctx, &tv);
>  }
> +#endif
>  
>  static void usb_host_add_fd(int fd, short events, void *user_data)
>  {
> +#ifdef CONFIG_PPOLL
>      qemu_set_fd_handler(fd,
>                          (events & POLLIN)  ? usb_host_handle_fd : NULL,
>                          (events & POLLOUT) ? usb_host_handle_fd : NULL,
>                          ctx);
> +#else
> +    g_assert(events == 0);
> +#endif
>  }
>  
>  static void usb_host_del_fd(int fd, void *user_data)

Hmm.  I'm wondering how libusb @ windows is notified about pending data.
Probably not using file descriptors but something else ...

I'd suggest to use CONFIG_WIN32 instead of CONFIG_POLL, to make clear
what this is about.  You can #ifdef out the whole block with all three
usb_host_*_fd functions, and the libusb call which registers these
callbacks somewhere further down in the code.  The later place should
probably get a /* FIXME */ in the #else branch as I expect we need to do
something on windows too.

cheers,
  Gerd