From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 89870C04AB6 for ; Fri, 31 May 2019 19:41:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 68D1326E74 for ; Fri, 31 May 2019 19:41:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727390AbfEaTlT (ORCPT ); Fri, 31 May 2019 15:41:19 -0400 Received: from smtprelay0192.hostedemail.com ([216.40.44.192]:36847 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726808AbfEaTlT (ORCPT ); Fri, 31 May 2019 15:41:19 -0400 Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay05.hostedemail.com (Postfix) with ESMTP id C6BDE1801BD6A; Fri, 31 May 2019 19:41:17 +0000 (UTC) X-Session-Marker: 6A6F6540706572636865732E636F6D X-HE-Tag: cork99_626698073144d X-Filterd-Recvd-Size: 5611 Received: from XPS-9350 (cpe-23-242-196-136.socal.res.rr.com [23.242.196.136]) (Authenticated sender: joe@perches.com) by omf12.hostedemail.com (Postfix) with ESMTPA; Fri, 31 May 2019 19:41:16 +0000 (UTC) Message-ID: Subject: Re: [PATCH] rtlwifi: remove redundant assignment to variable k From: Joe Perches To: Larry Finger , Colin King , Ping-Ke Shih , Kalle Valo , "David S . Miller" , linux-wireless@vger.kernel.org, netdev@vger.kernel.org Cc: kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org Date: Fri, 31 May 2019 12:41:14 -0700 In-Reply-To: <14372bed-6522-d81c-7d68-04adc0d71193@lwfinger.net> References: <20190531141412.18632-1-colin.king@canonical.com> <14372bed-6522-d81c-7d68-04adc0d71193@lwfinger.net> Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.30.1-1build1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2019-05-31 at 12:29 -0500, Larry Finger wrote: > On 5/31/19 9:14 AM, Colin King wrote: > > From: Colin Ian King > > > > The assignment of 0 to variable k is never read once we break out of > > the loop, so the assignment is redundant and can be removed. > > > > Addresses-Coverity: ("Unused value") > > Signed-off-by: Colin Ian King > > --- > > drivers/net/wireless/realtek/rtlwifi/efuse.c | 4 +--- > > 1 file changed, 1 insertion(+), 3 deletions(-) > > > > diff --git a/drivers/net/wireless/realtek/rtlwifi/efuse.c b/drivers/net/wireless/realtek/rtlwifi/efuse.c > > index e68340dfd980..83e5318ca04f 100644 > > --- a/drivers/net/wireless/realtek/rtlwifi/efuse.c > > +++ b/drivers/net/wireless/realtek/rtlwifi/efuse.c > > @@ -117,10 +117,8 @@ u8 efuse_read_1byte(struct ieee80211_hw *hw, u16 address) > > rtlpriv->cfg-> > > maps[EFUSE_CTRL] + 3); > > k++; > > - if (k == 1000) { > > - k = 0; > > + if (k == 1000) > > break; > > - } > > } > > data = rtl_read_byte(rtlpriv, rtlpriv->cfg->maps[EFUSE_CTRL]); > > return data; > > Colin, > > Your patch is not wrong, but it fails to address a basic deficiency of this code > snippet - when an error is detected, there is no attempt to either fix the > problem or report it upstream. As the data returned will be garbage if this > condition happens, we might as well replace the "break" with "return 0xFF", as > well as deleting the "k = 0" line. Most of the callers of efuse_read_1byte() > ignore the returned result when bits 0 and 4 are set, thus returning all 8 bits > is not a bad fixup. > > My suspicion is that this test is in the code merely to prevent an potential > unterminated "while" loop, and that this condition is extremely unlikely to happen. > > Larry The function is also overly verbose with many unnecessary rtlpriv->cfg->maps dereferences. I'd've written it more like: --- drivers/net/wireless/realtek/rtlwifi/efuse.c | 57 +++++++++++----------------- 1 file changed, 22 insertions(+), 35 deletions(-) diff --git a/drivers/net/wireless/realtek/rtlwifi/efuse.c b/drivers/net/wireless/realtek/rtlwifi/efuse.c index e68340dfd980..db253f45e87d 100644 --- a/drivers/net/wireless/realtek/rtlwifi/efuse.c +++ b/drivers/net/wireless/realtek/rtlwifi/efuse.c @@ -87,46 +87,33 @@ void efuse_initialize(struct ieee80211_hw *hw) u8 efuse_read_1byte(struct ieee80211_hw *hw, u16 address) { struct rtl_priv *rtlpriv = rtl_priv(hw); - u8 data; u8 bytetemp; u8 temp; - u32 k = 0; - const u32 efuse_len = - rtlpriv->cfg->maps[EFUSE_REAL_CONTENT_SIZE]; - - if (address < efuse_len) { - temp = address & 0xFF; - rtl_write_byte(rtlpriv, rtlpriv->cfg->maps[EFUSE_CTRL] + 1, - temp); - bytetemp = rtl_read_byte(rtlpriv, - rtlpriv->cfg->maps[EFUSE_CTRL] + 2); - temp = ((address >> 8) & 0x03) | (bytetemp & 0xFC); - rtl_write_byte(rtlpriv, rtlpriv->cfg->maps[EFUSE_CTRL] + 2, - temp); - - bytetemp = rtl_read_byte(rtlpriv, - rtlpriv->cfg->maps[EFUSE_CTRL] + 3); - temp = bytetemp & 0x7F; - rtl_write_byte(rtlpriv, rtlpriv->cfg->maps[EFUSE_CTRL] + 3, - temp); + int k = 0; + u32 *maps = rtlpriv->cfg->maps; + const u32 efuse_len = maps[EFUSE_REAL_CONTENT_SIZE]; - bytetemp = rtl_read_byte(rtlpriv, - rtlpriv->cfg->maps[EFUSE_CTRL] + 3); - while (!(bytetemp & 0x80)) { - bytetemp = rtl_read_byte(rtlpriv, - rtlpriv->cfg-> - maps[EFUSE_CTRL] + 3); - k++; - if (k == 1000) { - k = 0; - break; - } - } - data = rtl_read_byte(rtlpriv, rtlpriv->cfg->maps[EFUSE_CTRL]); - return data; - } else + if (address >= efuse_len) return 0xFF; + temp = address & 0xFF; + rtl_write_byte(rtlpriv, maps[EFUSE_CTRL] + 1, temp); + bytetemp = rtl_read_byte(rtlpriv, maps[EFUSE_CTRL] + 2); + temp = ((address >> 8) & 0x03) | (bytetemp & 0xFC); + rtl_write_byte(rtlpriv, maps[EFUSE_CTRL] + 2, temp); + + bytetemp = rtl_read_byte(rtlpriv, maps[EFUSE_CTRL] + 3); + temp = bytetemp & 0x7F; + rtl_write_byte(rtlpriv, maps[EFUSE_CTRL] + 3, temp); + + bytetemp = rtl_read_byte(rtlpriv, maps[EFUSE_CTRL] + 3); + while (!(bytetemp & 0x80)) { + bytetemp = rtl_read_byte(rtlpriv, maps[EFUSE_CTRL] + 3); + if (++k >= 1000) + return 0xFF; /* Likely defect */ + } + + return rtl_read_byte(rtlpriv, maps[EFUSE_CTRL]); } EXPORT_SYMBOL(efuse_read_1byte);