linux-kernel - Re: [PATCH v7 16/34] [media] add Omnivision OV5640 sensor driver

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Date:   Sun, 4 Jun 2017 11:00:14 -0700
From:   Steve Longerbeam <slongerbeam@...il.com>
To:     Sakari Ailus <sakari.ailus@....fi>
Cc:     robh+dt@...nel.org, mark.rutland@....com, shawnguo@...nel.org,
        kernel@...gutronix.de, fabio.estevam@....com,
        linux@...linux.org.uk, mchehab@...nel.org, hverkuil@...all.nl,
        nick@...anahar.org, markus.heiser@...marIT.de,
        p.zabel@...gutronix.de, laurent.pinchart+renesas@...asonboard.com,
        bparrot@...com, geert@...ux-m68k.org, arnd@...db.de,
        sudipm.mukherjee@...il.com, minghsiu.tsai@...iatek.com,
        tiffany.lin@...iatek.com, jean-christophe.trotin@...com,
        horms+renesas@...ge.net.au, niklas.soderlund+renesas@...natech.se,
        robert.jarzmik@...e.fr, songjun.wu@...rochip.com,
        andrew-ct.chen@...iatek.com, gregkh@...uxfoundation.org,
        shuah@...nel.org, sakari.ailus@...ux.intel.com, pavel@....cz,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
        devel@...verdev.osuosl.org,
        Steve Longerbeam <steve_longerbeam@...tor.com>
Subject: Re: [PATCH v7 16/34] [media] add Omnivision OV5640 sensor driver



On 06/03/2017 11:02 AM, Steve Longerbeam wrote:
> Hi Sakari,
> 
> 
> On 05/29/2017 11:56 PM, Sakari Ailus wrote:
>> Hi Steve,
>>
>> On Mon, May 29, 2017 at 02:50:34PM -0700, Steve Longerbeam wrote:
>>>> <snip>
>>>>
>>>>> +
>>>>> +static int ov5640_s_ctrl(struct v4l2_ctrl *ctrl)
>>>>> +{
>>>>> +    struct v4l2_subdev *sd = ctrl_to_sd(ctrl);
>>>>> +    struct ov5640_dev *sensor = to_ov5640_dev(sd);
>>>>> +    int ret = 0;
>>>>> +
>>>>> +    mutex_lock(&sensor->lock);
>>>> Could you use the same lock for the controls as you use for the 
>>>> rest? Just
>>>> setting handler->lock after handler init does the trick.
>>>
>>> Can you please rephrase, I don't follow. "same lock for the controls as
>>> you use for the rest" - there's only one device lock owned by this 
>>> driver
>>> and I am already using that same lock.
>>
>> There's another in the control handler. You could use your own lock 
>> for the
>> control handler as well.
> 
> I still don't understand.
> 

Hi Sakari, sorry I see what you are referring to now. The lock
in 'struct v4l2_ctrl_handler' can be overridden by a caller's own
lock. Yes that's a good idea, I'll do that.

Steve