From mboxrd@z Thu Jan 1 00:00:00 1970 From: Randy Dunlap Subject: Re: Bug introduced in the of_get_named_gpiod_flags function. Date: Wed, 10 Oct 2018 09:39:29 -0700 Message-ID: <4695559c-3f80-584a-c943-37a3bd9c24a7@infradead.org> References: <90dbf770-5262-5128-e585-c44d086568f9@ise.pw.edu.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <90dbf770-5262-5128-e585-c44d086568f9@ise.pw.edu.pl> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: wzab@ise.pw.edu.pl, LKML , Linus Walleij , "linux-gpio@vger.kernel.org" List-Id: linux-gpio@vger.kernel.org [adding linux-gpio + Linus W.] On 10/10/18 9:13 AM, wzab wrote: > Hi, > > The function of_get_named_gpiod_flags in older versions of the kernel > (up to 4.7.10 - https://elixir.bootlin.com/linux/v4.7.10/source/drivers/gpio/gpiolib-of.c#L75 ) > contained an important workaround: > > /* .of_xlate might decide to not fill in the flags, so clear it. */if (flags) > *flags = 0; Unfortunately, newer kernels do not contain it. Therefore if the > "xlat" function in the gpiochip driver does not set flags, (like e.g. > the Xilinx AXI GPIO driver: https://github.com/Xilinx/linux-xlnx/blob/c2ba891326bb472da59b6a2da29aca218d337687/drivers/gpio/gpio-xilinx.c#L262 ) > the random, unitialized value from the stack in of_find_gpio > ( https://elixir.bootlin.com/linux/v4.18.13/source/drivers/gpio/gpiolib-of.c#L228 ) > is used, which results in random settings of e.g., OPEN DRAIN or OPEN SOURCE mode. > > I have also reported the problem in the Xilinx forum: https://forums.xilinx.com/t5/Embedded-Linux/Bug-in-of-get-named-gpiod-flags-function-in-the-kernel-random/td-p/897695 > > With best regards, > Wojciech Zabolotny > > > -- ~Randy