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Message-ID: <4aaa46bf-26dd-fc4e-d4d9-7d0ee2028169@candelatech.com>
Date:   Mon, 5 Jun 2023 13:42:14 -0700
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Subject: Re: iwlwifi query on iwl_mvm_skb_prepare_status
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From:   Ben Greear <greearb@candelatech.com>
To:     linux-wireless <linux-wireless@vger.kernel.org>
References: <f8416cc9-6601-8c98-2a15-8ac5882833ce@candelatech.com>
Organization: Candela Technologies
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On 6/5/23 13:04, Ben Greear wrote:
> I think the two memsets below access the same memory since skb_info
> contains a union?  So maybe only one is needed?
> 
> static void iwl_mvm_skb_prepare_status(struct sk_buff *skb,
>                         struct iwl_device_tx_cmd *cmd)
> {
>      struct ieee80211_tx_info *skb_info = IEEE80211_SKB_CB(skb);
> 
>      memset(&skb_info->status, 0, sizeof(skb_info->status));
>      memset(skb_info->driver_data, 0, sizeof(skb_info->driver_data));
> 
>      skb_info->driver_data[1] = cmd;
> }

Also, maybe that driver_data[1] assigment is not helpful?  From what I can tell,
mvm is putting the iwl_device_tx_cmd pointer at driver_data[3], by way of some cb offsets.

Are these notes below valid for mvm?

/* skb->cb usage for mvm
  *
  * driver_data[0]: unused
  * driver_data[1]: holds pointer to struct iwl_device_tx_cmd (un-used???)
  * driver_data[2]: cb + cb_data_offs, points to mac header page.
  * driver_data[3]: dev_cmd_offs: cb + cb_data_offs + sizeof(void*), holds pointer to struct iwl_device_tx_cmd.
  * driver_data[4]: unused.
  */

> 
> Thanks,
> Ben
>