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Wed, 06 Nov 2019 06:00:16 -0800 (PST) Subject: Re: [PATCH 01/28] usb: common: change usb_debug_root as static variable To: Chunfeng Yun References: <8cb137d5376b4e317dc22dcb9e81a1125b781f8f.1573008519.git.chunfeng.yun@mediatek.com> <79fd2ebd-b8c6-ee00-c71e-782475a20de6@roeck-us.net> <1573031491.18464.70.camel@mhfsdcap03> From: Guenter Roeck Message-ID: <2e793636-04a6-8589-b4a5-259f79a5ea02@roeck-us.net> Date: Wed, 6 Nov 2019 06:00:11 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <1573031491.18464.70.camel@mhfsdcap03> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191106_060018_172565_672D3932 X-CRM114-Status: GOOD ( 21.69 ) X-BeenThere: linux-mediatek@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Chen , Alexandre Belloni , Heikki Krogerus , Wolfram Sang , Yangtao Li , Linus Walleij , linux-kernel@vger.kernel.org, Matthias Brugger , Mans Rullgard , Srinivas Kandagatla , Laurent Pinchart , Fabio Estevam , Florian Fainelli , Robert Jarzmik , Kevin Cernekee , "Gustavo A. R. Silva" , Ludovic Desroches , Alan Stern , NXP Linux Team , bcm-kernel-feedback-list@broadcom.com, David Kershner , Hans Ulli Kroll , Cristian Birsan , linux-media@vger.kernel.org, Fabrizio Castro , Mathias Payer , Mathias Nyman , Suzuki K Poulose , Sascha Hauer , Haojian Zhuang , Stephen Boyd , linux-mediatek@lists.infradead.org, Minas Harutyunyan , Simon Horman , Mauro Carvalho Chehab , Bin Liu , linux-arm-kernel@lists.infradead.org, Biju Das , Felipe Balbi , Laurentiu Tudor , Greg Kroah-Hartman , Yoshihiro Shimoda , linux-usb@vger.kernel.org, Nicolas Ferre , Dmitry Torokhov , Pengutronix Kernel Team , Colin Ian King , Shawn Guo , Daniel Mack Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "Linux-mediatek" Errors-To: linux-mediatek-bounces+linux-mediatek=archiver.kernel.org@lists.infradead.org On 11/6/19 1:11 AM, Chunfeng Yun wrote: > On Tue, 2019-11-05 at 20:03 -0800, Guenter Roeck wrote: >> On 11/5/19 7:15 PM, Chunfeng Yun wrote: >>> Try to avoid using extern global variable, and provide two >>> functions for the usage cases >>> >>> Signed-off-by: Chunfeng Yun >>> --- >>> drivers/usb/common/common.c | 16 ++++++++++++++-- >>> include/linux/usb.h | 5 ++++- >>> 2 files changed, 18 insertions(+), 3 deletions(-) >>> >>> diff --git a/drivers/usb/common/common.c b/drivers/usb/common/common.c >>> index 1433260d99b4..639ee6d243a2 100644 >>> --- a/drivers/usb/common/common.c >>> +++ b/drivers/usb/common/common.c >>> @@ -293,8 +293,20 @@ struct device *usb_of_get_companion_dev(struct device *dev) >>> EXPORT_SYMBOL_GPL(usb_of_get_companion_dev); >>> #endif >>> >>> -struct dentry *usb_debug_root; >>> -EXPORT_SYMBOL_GPL(usb_debug_root); >>> +static struct dentry *usb_debug_root; >>> + >> >> I don't think it is a good idea to declare this variable static >> before all its uses are removed. This patch will leave the system >> in a non-compileable state until all patches of the series have >> been applied. > Yes, you are right, I'll fix it, may be split into two patch > >> >> I am curious. What is the rationale for this change ? >> Did exported variables run out of favor ? > Personally, I think it's good practice to avoid global varibale, > it may not a good reason. Personally I don't think it is a good reason at all. When you are done, someone else may come in and declare the opposite, re-introduce the global variable, and drop the new functions as unnecessary. This is ok for new code, but I think we should leave existing code alone unless it is broken and needs to get fixed. This is not the case here. Thanks, Guenter _______________________________________________ Linux-mediatek mailing list Linux-mediatek@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-mediatek