Return-path: Received: from cn.fujitsu.com ([222.73.24.84]:64770 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1752503AbYIZIj4 (ORCPT ); Fri, 26 Sep 2008 04:39:56 -0400 Message-ID: <48DC9F31.4010807@cn.fujitsu.com> (sfid-20080926_104001_437100_81E82E6E) Date: Fri, 26 Sep 2008 16:37:05 +0800 From: Wang Chen MIME-Version: 1.0 To: "John W. Linville" CC: Dan Williams , "David S. Miller" , Jeff Garzik , NETDEV , linux-wireless@vger.kernel.org Subject: Re: [PATCH 14/18] netdevice airo: Convert directly reference of netdev->priv to netdev->ml_priv References: <48C0A219.2030004@cn.fujitsu.com> <48C0A72B.9050407@cn.fujitsu.com> <20080905125036.GA3027@tuxdriver.com> <1220634383.6430.14.camel@localhost.localdomain> <48C24F66.1090803@cn.fujitsu.com> In-Reply-To: <48C24F66.1090803@cn.fujitsu.com> Content-Type: text/plain; charset=UTF-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: Wang Chen said the following on 2008-9-6 17:37: >>>> We have some reasons to kill netdev->priv: >>>> 1. netdev->priv is equal to netdev_priv(). >>>> 2. netdev_priv() wraps the calculation of netdev->priv's offset, obviously >>>> netdev_priv() is more flexible than netdev->priv. >>>> But we cann't kill netdev->priv, because so many drivers reference to it >>>> directly. >>>> >>>> OK, becasue Dave S. Miller said, "every direct netdev->priv usage is a bug", >>>> and I want to kill netdev->priv later, I decided to convert all the direct >>>> reference of netdev->priv first. >>>> >>>> Different to readonly reference of netdev->priv, in this driver, netdev->priv >>>> was changed. I use netdev->ml_priv to replace netdev->priv. >>>> >>>> Signed-off-by: Wang Chen >>> Thank you for your patch. However, I do not understand why you didn't >>> simply replace netdev->priv with netdev_priv()? Can you explain? >> Yeah, that would have been my first choice too... >> > > 1. Why I don't use netdev_priv() to replace netdev->priv here? > Because, here >> @@ -2665,7 +2666,7 @@ static struct net_device *init_wifidev(struct airo_info *ai, >> struct net_device *dev = alloc_netdev(0, "wifi%d", wifi_setup); >> if (!dev) >> return NULL; >> - dev->priv = ethdev->priv; >> + dev->ml_priv = ethdev->ml_priv; >> @@ -2766,7 +2767,7 @@ static struct net_device *_init_airo_card( unsigned short irq, int port, >> return NULL; >> } >> >> - ai = dev->priv; >> + ai = dev->ml_priv = netdev_priv(dev); > netdev->priv was changed here, but it shouldn't, the memory was allocated when alloc_netdev and > netdev->priv should always pointed to that memory. > > 2. Why I use netdev->ml_priv here to replace netdev->priv? > In this driver, netdev->priv are shared by multi wifidevs, that means wifidevs need > mid-layer private data, which are all same as their parent netdev. > This usage is same as Dave's commit "syncppp: Fix crashes." > John, do you have any comments about my answer?