netdev - Re: [PATCH v2 net] nfp: cast sizeof() to int when comparing with error code

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Message-ID: <308957d91294ec1883ec492eecb8ffe1d51a0689.camel@perches.com>
Date:   Mon, 25 Jun 2018 19:29:59 -0700
From:   Joe Perches <joe@...ches.com>
To:     Chengguang Xu <cgxu519@....com>, jakub.kicinski@...ronome.com,
        davem@...emloft.net
Cc:     oss-drivers@...ronome.com, netdev@...r.kernel.org
Subject: Re: [PATCH v2 net] nfp: cast sizeof() to int when comparing with
 error code

On Tue, 2018-06-26 at 09:16 +0800, Chengguang Xu wrote:
> sizeof() will return unsigned value so in the error check
> negative error code will be always larger than sizeof().
[]
> diff --git a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nffw.c b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nffw.c
[]
> @@ -232,7 +232,7 @@ struct nfp_nffw_info *nfp_nffw_info_open(struct nfp_cpp *cpp)
>  	err = nfp_cpp_read(cpp, nfp_resource_cpp_id(state->res),
>  			   nfp_resource_address(state->res),
>  			   fwinf, sizeof(*fwinf));
> -	if (err < sizeof(*fwinf))
> +	if (err < (int)sizeof(*fwinf))
>  		goto err_release;
>  
>  	if (!nffw_res_flg_init_get(fwinf))

The way this is done in several places in the kernel is
to test first for < 0 and then test for < sizeof

	if (err < 0 || err < sizeof(etc...)

see net/ceph/ceph_common.c etc...