Date:   Fri, 4 Nov 2016 01:40:29 +0200
From:   Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>
To:     Sakari Ailus <sakari.ailus@....fi>,
        Sebastian Reichel <sre@...nel.org>
Cc:     Pavel Machek <pavel@....cz>, pali.rohar@...il.com,
        linux-media@...r.kernel.org, galak@...eaurora.org,
        mchehab@....samsung.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] media: Driver for Toshiba et8ek8 5MP sensor

Hi,

On  4.11.2016 01:05, Sakari Ailus wrote:
> Hi Sebastian,
>
> On Thu, Nov 03, 2016 at 11:48:43PM +0100, Sebastian Reichel wrote:
>> Hi,
>>
>> On Tue, Nov 01, 2016 at 12:54:08AM +0200, Sakari Ailus wrote:
>>>>> Thanks, this answered half of my questions already. ;-)
>>>> :-).
>>>>
>>>> I'll have to go through the patches, et8ek8 driver is probably not
>>>> enough to get useful video. platform/video-bus-switch.c is needed for
>>>> camera switching, then some omap3isp patches to bind flash and
>>>> autofocus into the subdevice.
>>>>
>>>> Then, device tree support on n900 can be added.
>>>
>>> I briefly discussed with with Sebastian.
>>>
>>> Do you think the elusive support for the secondary camera is worth keeping
>>> out the main camera from the DT in mainline? As long as there's a reasonable
>>> way to get it working, I'd just merge that. If someone ever gets the
>>> secondary camera working properly and nicely with the video bus switch,
>>> that's cool, we'll somehow deal with the problem then. But frankly I don't
>>> think it's very useful even if we get there: the quality is really bad.
>>
>> If we want to keep open the option to add proper support for the
>> second camera, we could also add the bus switch and not add the
>> front camera node in DT. Then adding the front camera does not
>> require DT or userspace API changes. It would need an additional
>> DT quirk in arch/arm/mach-omap2/board-generic.c for RX51, which
>> adds the CCP2 bus settings from the camera node to the bus
>> switch node to keep isp_of_parse_node happy. That should be
>> easy to implement and not add much delay in upstreaming.
>
> By adding the video bus switch we have a little bit more complex system as a
> whole. The V4L2 async does not currently support this. There's more here:
>
> <URL:http://www.spinics.net/lists/linux-media/msg107262.html>
>
> What I thought was that once we have everything that's required in place, we
> can just change what's in DT. But the software needs to continue to work
> with the old DT content.
>
>> For actually getting both cameras available with runtime-switching
>> the proper solution would probably involve moving the parsing of
>> the bus-settings to the sensor driver and providing a callback.
>> This callback can be called by omap3isp when it wants to configure
>> the phy (which is basically when it starts streaming). That seems
>> to be the only place needing the buscfg anyways.
>>
>> Then the video-bus-switch could do something like this (pseudocode):
>>
>> static void get_buscfg(struct *this, struct *buscfg) {
>>     if (selected_cam == 0)
>>         return this->sensor_a->get_buscfg(buscfg);
>>     else
>>         return this->sensor_b->get_buscfg(buscfg);
>> }
>>
>> Regarding the usefulness: I noticed, that the Neo900 people also
>> plan to have the bus-switch [0]. It's still the same crappy front-cam,
>> though. Nevertheless it might be useful for testing. It has nice
>> test-image capabilities, which might be useful for regression
>> testing once everything is in place.
>>
>> [0] http://neo900.org/stuff/block-diagrams/neo900/neo900.html
>
> Seriously? I suppose there should be no need for that anymore, is there?
>
> I think they wanted to save one GPIO in order to shave off 0,0001 cents from
> the manufacturing costs or something like that. And the result is...
> painful. :-I
>

No, the reason is that hey want to keep Neo900 as close as possible to 
N900, HW wise

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