linux-kernel - Re: [PATCH] [RESEND] [media] omap3isp: support 64-bit version of omap3isp_stat

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Message-ID: <CAK8P3a0M5iKCXmKwQAzd9EKWo7Sr_0OR82Q=ozmj3f3Xtyde6A@mail.gmail.com>
Date:   Thu, 3 May 2018 18:06:58 -0400
From:   Arnd Bergmann <arnd@...db.de>
To:     Sakari Ailus <sakari.ailus@....fi>
Cc:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] [RESEND] [media] omap3isp: support 64-bit version of omap3isp_stat_data

On Thu, May 3, 2018 at 8:56 AM, Sakari Ailus <sakari.ailus@....fi> wrote:
> On Wed, Apr 25, 2018 at 11:30:10PM +0200, Arnd Bergmann wrote:
>> @@ -165,7 +167,14 @@ struct omap3isp_h3a_aewb_config {
>>   * @config_counter: Number of the configuration associated with the data.
>>   */
>>  struct omap3isp_stat_data {
>> +#ifdef __KERNEL__
>> +     struct {
>> +             __s64   tv_sec;
>> +             __s64   tv_usec;
>
> Any particular reason for __s64 here instead of e.g. long or __s32? Kernel
> appears to use long in the timespec64 definition.

The user space 'timeval' definition is 16 bytes wide, with the layout
designed to be compatible between 32-bit and 64-bit, so it has to be like
this to match what user spaces sees with the old header files and a new
libc.

We don't yet know what the exact definition of timeval will be in all
libc implementations, but if they have a 32-bit tv_user field, it needs
padding next to it so the lower 32 bits are in the same place as they
would be using that 64-bit field I used.

         Arnd