From mboxrd@z Thu Jan  1 00:00:00 1970
Return-path: <linux-media-owner@vger.kernel.org>
Received: from mail-qt0-f193.google.com ([209.85.216.193]:35487 "EHLO
        mail-qt0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1755260AbeCHKAr (ORCPT
        <rfc822;linux-media@vger.kernel.org>); Thu, 8 Mar 2018 05:00:47 -0500
MIME-Version: 1.0
In-Reply-To: <d98ac356-a482-f26f-fd6b-6142281d99c3@xs4all.nl>
References: <1514533978-20408-1-git-send-email-zhengsq@rock-chips.com>
 <1514533978-20408-4-git-send-email-zhengsq@rock-chips.com> <d98ac356-a482-f26f-fd6b-6142281d99c3@xs4all.nl>
From: Jacob Chen <jacobchen110@gmail.com>
Date: Thu, 8 Mar 2018 18:00:45 +0800
Message-ID: <CAFLEztSsg+EW97AN93gd-rx7A1bNwfHK5e9MpLnem40ATnfsrw@mail.gmail.com>
Subject: Re: [PATCH v5 03/16] media: rkisp1: Add user space ABI definitions
To: Hans Verkuil <hverkuil@xs4all.nl>
Cc: Shunqian Zheng <zhengsq@rock-chips.com>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@lists.infradead.org>,
        Linux Media Mailing List <linux-media@vger.kernel.org>,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        Hans Verkuil <hans.verkuil@cisco.com>,
        Tomasz Figa <tfiga@chromium.org>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        =?UTF-8?B?6ZKf5Lul5bSH?= <zyc@rock-chips.com>,
        Eddie Cai <eddie.cai.linux@gmail.com>,
        Jeffy Chen <jeffy.chen@rock-chips.com>,
        Allon Huang <allon.huang@rock-chips.com>,
        devicetree@vger.kernel.org, Heiko Stuebner <heiko@sntech.de>,
        robh+dt@kernel.org, Joao Pinto <Joao.Pinto@synopsys.com>,
        Luis Oliveira <Luis.Oliveira@synopsys.com>,
        Jose Abreu <Jose.Abreu@synopsys.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-media-owner@vger.kernel.org
List-ID: <linux-media.vger.kernel.org>

Hi Hans,

2018-02-07 20:00 GMT+08:00 Hans Verkuil <hverkuil@xs4all.nl>:
> On 12/29/17 08:52, Shunqian Zheng wrote:
>> From: Jeffy Chen <jeffy.chen@rock-chips.com>
>>
>> Add the header for userspace
>
> General note: I saw four cases where this documentation referred to the
> datasheet. Three comments on that:
>
> 1) You don't say which datasheet.
> 2) I assume the datasheet is under NDA?

This datasheet can't be got by customers, even under NDA.

> 3) You do need to give enough information so a reasonable default can be
>    used. I mentioned in an earlier review that creating an initial params
>    struct that can be used as a templete would be helpful (or even
>    required), and that would be a good place to put such defaults.
>

It don't need a default config
For applcation writers, they can just init it with zero data, and only
set value for the part they concerned.

As for ABI, i have checked there is no mismatches.
Those structures is 32 bit aligned both in 64bit/32bit env, since
there is no 64bit value.
"__attribute__ ((packed))" can avoid mismatches happen when we add a
64bit value to those structures.

As robin said, enums and bools are not guaranteed to be consistent
between different compiler, so it's a potential risk.
I have replace bools with unsigned char and enums with unsigned int.


> Regards,
>
>         Hans