Re: [PATCH 2/3] net: Restore printing of the help text with "-nic help"

[Claudio Fontana]

On 11/10/22 13:05, Claudio Fontana wrote:
> On 11/10/22 12:42, Thomas Huth wrote:
>> On 08/11/2022 10.49, Claudio Fontana wrote:
>>> On 11/4/22 13:57, Thomas Huth wrote:
>>>> Running QEMU with "-nic help" used to work in QEMU 5.2 and earlier versions
>>>> (it showed the available netdev backends), but this feature got broken 
>>>> during
>>>> some refactoring in version 6.0. Let's restore the old behavior, and while
>>>> we're at it, let's also print the available NIC models here now since this
>>>> option can be used to configure both, netdev backend and model in one go.
>>>>
>>>> Fixes: ad6f932fe8 ("net: do not exit on "netdev_add help" monitor command")
>>>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>>>> ---
>>>>   net/net.c | 14 ++++++++++++--
>>>>   1 file changed, 12 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/net/net.c b/net/net.c
>>>> index c0516a8067..b4b8f2a9cc 100644
>>>> --- a/net/net.c
>>>> +++ b/net/net.c
>>>> @@ -1571,8 +1571,18 @@ static int net_param_nic(void *dummy, QemuOpts 
>>>> *opts, Error **errp)
>>>>       const char *type;
>>>>   
>>>>       type = qemu_opt_get(opts, "type");
>>>> -    if (type && g_str_equal(type, "none")) {
>>>> -        return 0;    /* Nothing to do, default_net is cleared in vl.c */
>>>> +    if (type) {
>>>> +        if (g_str_equal(type, "none")) {
>>>> +            return 0;    /* Nothing to do, default_net is cleared in vl.c 
>>>> */
>>>> +        }
>>>> +        if (is_help_option(type)) {
>>>> +            GPtrArray *nic_models = qemu_get_nic_models(TYPE_DEVICE);
>>>> +            show_netdevs();
>>>> +            printf("\n");
>>>> +            qemu_show_nic_models(type, (const char **)nic_models->pdata);
>>>> +            g_ptr_array_free(nic_models, true);
>>>
>>> nit: would not the order:
>>>
>>>> +            GPtrArray *nic_models;
>>>> +            show_netdevs();
>>>> +            printf("\n");
>>>> +            nic_models = qemu_get_nic_models(TYPE_DEVICE);
>>>> +            qemu_show_nic_models(type, (const char **)nic_models->pdata);
>>>> +            g_ptr_array_free(nic_models, true);
>>>
>>> flow more logically?
>>
>> I think that's mostly a matter of taste ...
> 
> To some extent, but for the reader it would make more sense not to intermix 
> unrelated code?
> 
> I'd say:
> 
> - show_netdevs
> _ get nic models
> - show nic models
> 
> instead of:
> 
> - get nic models
> - show netdevs
> - show nic models
> 
> 
>  > and as long as the declaration 
>> of the variable has to stay at the top of the block (according to QEMU's 
>> coding style), I think I'd also prefer to keep the initialization there.
>>
> 
> This conflict can easily be solved by putting the nic_models on its own line,
> as I have shown in my hunk above.
>

And another option (not used enough in QEMU code imo), is to open a block 
specifically for the nic models.

Ie you can say:

 show_netdevs();
 printf("\n");
 {
     GPtrArray *nic_models = qemu_get_nic_models(TYPE_DEVICE);
     qemu_show_nic_models(type, (const char **)nic_models->pdata);
     g_ptr_array_free(nic_models, true);
 }

this even has the additional benefit of making the allocation/free of the 
nic_models clearer as it corresponds to the block.

C