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s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=T5ZH6tpiwfQ5fkv123INJrXWMFwMdaXrCNUYVgSIWI4=; b=Amb5mqWiMyKNTNjUV/N98xWyF+NM5+2By/9HxLpzXXagFhlZNQJE8AUiKnvxP/xcHE sDCh2vAG0NeqBdwQBidQmxsjyYzMOh73Fj5HIX6lpnEUBwP7JENk7uXjvxzRq/IqzaoH yLomSk55NK5CfwVayVAln2BH3HWdAAHObDD4IZsdQIIQO/Dd8RIUUIzOM6Yz/p+COzqw zDo8m77chHu6m8ll8yktHmeTRGajcHsd/8LpKc5q2/EkA0i1iUJRv9qsD2R5UjwO9IU6 6rvpQlVbTJ0pHCcmsdNhZwy0nOnH/PS1aCn87M9FgluzIvMWo79M12/JseWLPMe6blGz F+Kw== X-Gm-Message-State: AOAM532zUgC4RvdiK86me011uIlKYQqOTFwr/fdDmtJLEgzluW5VfRAq me42c20wp6lRUKZ/iJVCUDjfms1LCxXi/kIiEJLTpHMP+GBv2A== X-Google-Smtp-Source: ABdhPJywjOk7vZxGOJJADXbQK4tIIqhiK4TeZPZSPtyi3/XubxpIX3IXQbGCy9TL1N/HXNeWieEVbbkpxJTBGX+go9I= X-Received: by 2002:a50:99d5:: with SMTP id n21mr3214899edb.88.1599644506197; Wed, 09 Sep 2020 02:41:46 -0700 (PDT) MIME-Version: 1.0 References: <20200905133549.24606-1-warthog618@gmail.com> <20200905133549.24606-8-warthog618@gmail.com> <20200909092401.GA1431678@sol> <20200909093523.GA1506132@sol> In-Reply-To: <20200909093523.GA1506132@sol> From: Bartosz Golaszewski Date: Wed, 9 Sep 2020 11:41:35 +0200 Message-ID: Subject: Re: [PATCH v7 07/20] gpiolib: cdev: support GPIO_V2_GET_LINE_IOCTL and GPIO_V2_LINE_GET_VALUES_IOCTL To: Kent Gibson Cc: LKML , linux-gpio , Linus Walleij Content-Type: text/plain; charset="UTF-8" Sender: linux-gpio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org On Wed, Sep 9, 2020 at 11:35 AM Kent Gibson wrote: > > On Wed, Sep 09, 2020 at 11:26:00AM +0200, Bartosz Golaszewski wrote: > > On Wed, Sep 9, 2020 at 11:24 AM Kent Gibson wrote: > > > > > > On Sat, Sep 05, 2020 at 09:35:36PM +0800, Kent Gibson wrote: > > > > Add support for requesting lines using the GPIO_V2_GET_LINE_IOCTL, and > > > > returning their current values using GPIO_V2_LINE_GET_VALUES_IOCTL. > > > > > > > > The struct linereq implementation is based on the v1 struct linehandle > > > > implementation. > > > > > > > > Signed-off-by: Kent Gibson > > > > --- > > > > > > > > > > [snip] > > > > > > > if (copy_from_user(&offset, ip, sizeof(offset))) > > > > return -EFAULT; > > > > @@ -1104,6 +1505,25 @@ int gpiolib_cdev_register(struct gpio_device *gdev, dev_t devt) > > > > MAJOR(devt), gdev->id); > > > > > > > > return 0; > > > > + /* > > > > + * array sizes must ensure 64-bit alignment and not create holes in > > > > + * the struct packing. > > > > + */ > > > > + BUILD_BUG_ON(IS_ALIGNED(GPIO_V2_LINES_MAX, 2)); > > > > + BUILD_BUG_ON(IS_ALIGNED(GPIO_MAX_NAME_SIZE, 8)); > > > > + > > > > + /* > > > > + * check that uAPI structs are 64-bit aligned for 32/64-bit > > > > + * compatibility > > > > + */ > > > > + BUILD_BUG_ON(IS_ALIGNED(sizeof(struct gpio_v2_line_attribute), 8)); > > > > + BUILD_BUG_ON(IS_ALIGNED(sizeof(struct gpio_v2_line_config_attribute), 8)); > > > > + BUILD_BUG_ON(IS_ALIGNED(sizeof(struct gpio_v2_line_config), 8)); > > > > + BUILD_BUG_ON(IS_ALIGNED(sizeof(struct gpio_v2_line_request), 8)); > > > > + BUILD_BUG_ON(IS_ALIGNED(sizeof(struct gpio_v2_line_info), 8)); > > > > + BUILD_BUG_ON(IS_ALIGNED(sizeof(struct gpio_v2_line_info_changed), 8)); > > > > + BUILD_BUG_ON(IS_ALIGNED(sizeof(struct gpio_v2_line_event), 8)); > > > > + BUILD_BUG_ON(IS_ALIGNED(sizeof(struct gpio_v2_line_values), 8)); > > > > } > > > > > > > > > > A couple of things here - these should all be !IS_ALIGNED. > > > And the BUILD_BUG_ON gets compiled out, and so doesn't fail, if they are > > > after the return. > > > > > > How would you like that fixed - v8 or a patch once v7 is in? > > > > > > Cheers, > > > Kent. > > > > v8 please. Why is it compiled out though? Does it need some config option? > > > > Not sure - haven't looked into it. I only noticed the condition was > inverted in passing, and when I flipped it it still compiled. > Moving the return to the end of the function made them all fail, > as they should if IS_ALIGNED is true. > > Having BUILD_BUG_ON being able to compile out quietly is a problem in > itself. Nothing special in my setup that I am aware of. > > Cheers, > Kent. >From include/linux/compiler_types.h: 295 #ifdef __OPTIMIZE__ 296 # define __compiletime_assert(condition, msg, prefix, suffix) \ 297 do { \ 298 extern void prefix ## suffix(void) __compiletime_error(msg); \ 299 if (!(condition)) \ 300 prefix ## suffix(); \ 301 } while (0) 302 #else 303 # define __compiletime_assert(condition, msg, prefix, suffix) do { } while (0) 304 #endif __OPTIMIZE__ is a predefined macro. I'm not sure about your setup but it it's defined for me in all my yocto SDK builds and BUILD_BUG_ON(1) fails as expected. Bartosz