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From:   Kalle Valo <kvalo@codeaurora.org>
To:     "Bjoern A. Zeeb" <bz@FreeBSD.ORG>
Cc:     linux-wireless@vger.kernel.org, luciano.coelho@intel.com
Subject: Re: [PATCH iwlwifi-next] iwlwifi: fix 'arithmetic on a pointer to void' errors
References: <alpine.BSF.2.00.2102261651340.72241@ai.fobar.qr>
Date:   Mon, 01 Mar 2021 09:29:43 +0200
In-Reply-To: <alpine.BSF.2.00.2102261651340.72241@ai.fobar.qr> (Bjoern A.
        Zeeb's message of "Fri, 26 Feb 2021 16:52:07 +0000 (UTC)")
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"Bjoern A. Zeeb" <bz@FreeBSD.ORG> writes:

> Compiling the code with clang on FreeBSD complains about:
>   arithmetic on a pointer to void is a GNU extension
>       [-Werror,-Wpointer-arith].
> Cast to (u8 *) for the arithmetic operation and then back to
> the requested type or apply () before casting to avoid errors
> and have a defined behaviour.
>
> Sponsored-by:  The FreeBSD Foundation
> Signed-off-by: Bjoern A. Zeeb <bz@FreeBSD.ORG>

[...]

> -		range = range + range_size;
> +		range = (void *)((u8 *)range + range_size);

I think "(void *)" is not needed here.

>  static int iwl_mvm_scan_umac(struct iwl_mvm *mvm, struct ieee80211_vif *vif,
>  			     struct iwl_mvm_scan_params *params,
>  			     int type, int uid)
>  {
>  	struct iwl_scan_req_umac *cmd = mvm->scan_cmd;
>  	struct iwl_scan_umac_chan_param *chan_param;
>  	void *cmd_data = iwl_mvm_get_scan_req_umac_data(mvm);
> -	void *sec_part = cmd_data + sizeof(struct iwl_scan_channel_cfg_umac) *
> -		mvm->fw->ucode_capa.n_scan_channels;
> +	void *sec_part = (void *)((u8 *)cmd_data +
> +		sizeof(struct iwl_scan_channel_cfg_umac) *
> +		mvm->fw->ucode_capa.n_scan_channels);

Not needed here as well.

> @@ -151,28 +151,28 @@ static inline void iwl_pcie_tfd_set_tb(struct iwl_trans *trans, void *tfd,
>  static int iwl_pcie_txq_build_tfd(struct iwl_trans *trans, struct iwl_txq *txq,
>  				  dma_addr_t addr, u16 len, bool reset)
>  {
>  	void *tfd;
>  	u32 num_tbs;
>
> -	tfd = txq->tfds + trans->txqs.tfd.size * txq->write_ptr;
> +	tfd = (void *)((u8 *)txq->tfds + trans->txqs.tfd.size * txq->write_ptr);

And not here.

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