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Date: Mon, 18 Apr 2011 15:13:33 +0200
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] Question about total_sectors in block/vpc.c
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To: Lyu Mitnick <mitnick.lyu@gmail.com>
Cc: Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel@nongnu.org, Christoph Hellwig <hch@lst.de>

Am 15.04.2011 22:40, schrieb Lyu Mitnick:
> Hello Kevin,
> 
> 2011/4/14 Kevin Wolf <kwolf@redhat.com <mailto:kwolf@redhat.com>>
> 
>     Am 13.04.2011 22:59, schrieb Lyu Mitnick:
>     > Hello Stefan,
>     >
>     > I have a question about get_option_parameter(). I am wondering whether
>     > get_option_parameter  is suitable to use instead of doing the
>     search by
>     > myself
>     > in the case like following:
>     >
>     > /* Read out options */
>     >     while (options && options->name) {
>     >         if (!strcmp(options->name, BLOCK_OPT_SIZE)) {
>     >             // do something
>     >         } else if (!strcmp(options->name, BLOCK_OPT_CLUSTER_SIZE)) {
>     >            // do something
>     >         }
>     >         options++;
>     >     }
> 
>     Yes, I think it is, though you need to check whether the option has been
>     set in order to allow use default values.
> 
>     Kevin
> 
> 
> I have no idea about the mean of "check whether the option has been set in 
> order to allow use default values" , would you mind to give me an
> example about 
> it??
> 
> So as the example above. I am wondering whether the code should be
> rewritten 
> as:
> 
> /* Read out options */
> if(get_option_parameter(options, BLOCK_OPT_SIZE)) {
>     // do something
> }
> 
> if (get_option_parameter(options, BLOCK_OPT_CLUSTER_SIZE)) {
>     // do something
> }

get_option_parameter would never return NULL in your example.

Kevin