Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH v8 05/14] media: rkisp1: add Rockchip ISP1 subdev driver
To:     Sakari Ailus <sakari.ailus@linux.intel.com>,
        Helen Koike <helen.koike@collabora.com>
Cc:     linux-rockchip@lists.infradead.org, devicetree@vger.kernel.org,
        eddie.cai.linux@gmail.com, mchehab@kernel.org, heiko@sntech.de,
        jacob2.chen@rock-chips.com, jeffy.chen@rock-chips.com,
        zyc@rock-chips.com, linux-kernel@vger.kernel.org,
        tfiga@chromium.org, hans.verkuil@cisco.com,
        laurent.pinchart@ideasonboard.com, kernel@collabora.com,
        ezequiel@collabora.com, linux-media@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, zhengsq@rock-chips.com,
        Jacob Chen <cc@rock-chips.com>,
        Allon Huang <allon.huang@rock-chips.com>,
        Dafna Hirschfeld <dafna3@gmail.com>
References: <20190730184256.30338-1-helen.koike@collabora.com>
 <20190730184256.30338-6-helen.koike@collabora.com>
 <20190808091406.GQ21370@paasikivi.fi.intel.com>
 <da6c1d01-e3f6-ad73-db55-145d7832a665@collabora.com>
 <20190815082422.GM6133@paasikivi.fi.intel.com>
 <20190815131748.GS6133@paasikivi.fi.intel.com>
From:   Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Message-ID: <78856358-1afd-31a7-86dd-22f7d6d7fb05@collabora.com>
Date:   Fri, 31 Jan 2020 20:38:34 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.4.1
MIME-Version: 1.0
In-Reply-To: <20190815131748.GS6133@paasikivi.fi.intel.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi,
I (Dafna Hirschfeld) will work in following months with Helen Koike to fix the issues
in the TODO file of this driver: drivers/staging/media/rkisp1/TODO

On 15.08.19 15:17, Sakari Ailus wrote:
> On Thu, Aug 15, 2019 at 11:24:22AM +0300, Sakari Ailus wrote:
>> Hi Helen,
>>
>> On Wed, Aug 14, 2019 at 09:58:05PM -0300, Helen Koike wrote:
>>
>> ...
>>
>>>>> +static int rkisp1_isp_sd_set_fmt(struct v4l2_subdev *sd,
>>>>> +				 struct v4l2_subdev_pad_config *cfg,
>>>>> +				 struct v4l2_subdev_format *fmt)
>>>>> +{
>>>>> +	struct rkisp1_device *isp_dev = sd_to_isp_dev(sd);
>>>>> +	struct rkisp1_isp_subdev *isp_sd = &isp_dev->isp_sdev;
>>>>> +	struct v4l2_mbus_framefmt *mf = &fmt->format;
>>>>> +
>>>>
>>>> Note that for sub-device nodes, the driver is itself responsible for
>>>> serialising the access to its data structures.
>>>
>>> But looking at subdev_do_ioctl_lock(), it seems that it serializes the
>>> ioctl calls for subdevs, no? Or I'm misunderstanding something (which is
>>> most probably) ?
>>
>> Good question. I had missed this change --- subdev_do_ioctl_lock() is
>> relatively new. But setting that lock is still not possible as the struct

'the struct' - do you mean the 'vdev' struct allocated in
'v4l2_device_register_subdev_nodes' ?

>> is allocated in the framework and the device is registered before the

>> driver gets hold of it. It's a good idea to provide the same serialisation
>> for subdevs as well.
>>
>> I'll get back to this later.
> 
> The main reason is actually that these ops are also called through the
> sub-device kAPI, not only through the uAPI, and the locks are only taken
> through the calls via uAPI.

actually it seems that although 'subdev_do_ioctl_lock' exit, I wonder if
any subdevice uses that vdev->lock in  subdev_do_ioctl_lock.
It is not initialized in v4l2_device_register_subdev_nodes where the vdev is allocated
and I wonder if any subdevice actually initialize it somewhere else. For example it is null in this
driver and in vimc.

> 
> So adding the locks to uAPI calls alone would not address the issue.

What I can do is add a mutex to every struct of a subdevice and lock it
at the beginning of each subdevice operation.
Is this an acceptable solution?

Thanks,
Dafna
>