Re: [Qemu-devel] [PATCH 01/12] monitor: use monitor_handle_fd_param for non-Error-friendly users of named fds

[Luiz Capitulino <lcapitulino@redhat.com>]

On Wed, 19 Sep 2012 16:31:04 +0200
Paolo Bonzini <pbonzini@redhat.com> wrote:

> monitor_handle_fd_param and monitor_get_fd are mostly the same, except
> that monitor_handle_fd_param does error reporting wrong.  Use it in all
> other places that do it wrong, instead of reinventing it.

Hmm, why do we want to do this?

As far as I understand it the main difference between the two functions
is that if fdname is a number (for a weak definition of number),
monitor_handle_fd_param() assumes that the fd already exists in qemu
(eg. it was passed by the parent process). 

I don't like much the idea of spreading its usage because if it's
used by a qmp command (and this patch does just that) then clients
using that command won't be able to set the first character of fdname
to a number, IOW it's an incompatible change (unless this doesn't work
today for some reason, but I believe it does).

Another side effect is that you add the possibility of functions
changing from monitor_get_fd() to monitor_handle_fd_param() to also take
fds passed by the parent process. Might be positive, but I wonder if that's
useful for the commands you're changing.

> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  hw/kvm/pci-assign.c | 4 +---
>  migration-fd.c      | 3 +--
>  monitor.c           | 6 +++---
>  3 file modificati, 5 inserzioni(+), 8 rimozioni(-)
> 
> diff --git a/hw/kvm/pci-assign.c b/hw/kvm/pci-assign.c
> index 05b93d9..8b96a57 100644
> --- a/hw/kvm/pci-assign.c
> +++ b/hw/kvm/pci-assign.c
> @@ -582,10 +582,8 @@ static int get_real_device(AssignedDevice *pci_dev, uint16_t r_seg,
>          if (qemu_isdigit(pci_dev->configfd_name[0])) {
>              dev->config_fd = strtol(pci_dev->configfd_name, NULL, 0);
>          } else {
> -            dev->config_fd = monitor_get_fd(cur_mon, pci_dev->configfd_name);
> +            dev->config_fd = monitor_handle_fd_param(cur_mon, pci_dev->configfd_name);
>              if (dev->config_fd < 0) {
> -                error_report("%s: (%s) unkown", __func__,
> -                             pci_dev->configfd_name);
>                  return 1;
>              }
>          }
> diff --git a/migration-fd.c b/migration-fd.c
> index 50138ed..3eb53d9 100644
> --- a/migration-fd.c
> +++ b/migration-fd.c
> @@ -75,9 +75,8 @@ static int fd_close(MigrationState *s)
>  
>  int fd_start_outgoing_migration(MigrationState *s, const char *fdname)
>  {
> -    s->fd = monitor_get_fd(cur_mon, fdname);
> +    s->fd = monitor_handle_fd_param(cur_mon, fdname);
>      if (s->fd == -1) {
> -        DPRINTF("fd_migration: invalid file descriptor identifier\n");
>          goto err_after_get_fd;
>      }
>  
> diff --git a/monitor.c b/monitor.c
> index 67064e2..4901600 100644
> --- a/monitor.c
> +++ b/monitor.c
> @@ -951,7 +951,7 @@ static int add_graphics_client(Monitor *mon, const QDict *qdict, QObject **ret_d
>      CharDriverState *s;
>  
>      if (strcmp(protocol, "spice") == 0) {
> -        int fd = monitor_get_fd(mon, fdname);
> +        int fd = monitor_handle_fd_param(mon, fdname);
>          int skipauth = qdict_get_try_bool(qdict, "skipauth", 0);
>          int tls = qdict_get_try_bool(qdict, "tls", 0);
>          if (!using_spice) {
> @@ -965,13 +965,13 @@ static int add_graphics_client(Monitor *mon, const QDict *qdict, QObject **ret_d
>          return 0;
>  #ifdef CONFIG_VNC
>      } else if (strcmp(protocol, "vnc") == 0) {
> -	int fd = monitor_get_fd(mon, fdname);
> +	int fd = monitor_handle_fd_param(mon, fdname);
>          int skipauth = qdict_get_try_bool(qdict, "skipauth", 0);
>  	vnc_display_add_client(NULL, fd, skipauth);
>  	return 0;
>  #endif
>      } else if ((s = qemu_chr_find(protocol)) != NULL) {
> -	int fd = monitor_get_fd(mon, fdname);
> +	int fd = monitor_handle_fd_param(mon, fdname);
>  	if (qemu_chr_add_client(s, fd) < 0) {
>  	    qerror_report(QERR_ADD_CLIENT_FAILED);
>  	    return -1;