Re: [RFC] V4L2 API for flash devices

[Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>]

Kim HeungJun wrote:
> Hi Sakari,

Hi,

> 2011. 3. 30., 오후 8:37, Sakari Ailus 작성:
> 
>> Kim, HeungJun wrote:
>>> Hi Sakari,
>>
>> Hi HeungJun,
>>
>>> 2011-03-29 오후 11:41, Sakari Ailus 쓴 글:
>>>> Kim, HeungJun wrote:
>>> [snip]
>>>>> I think it's not different method to turn on/off, whatever the mode name is.
>>>>> But, the mode name DEDICATED is look more reasonable, because the reason 
>>>>> which is devided FLASH and TORCH in the mode, is why only power up the led,
>>>>> not sensor.
>>>>
>>>> Sensor? Is the flash part of the sensor module for you?
>>> Yes. The flash is a part of the sensor module(our case like M-5MOLS).
>>> Precisely, the sensor internal core's gpio pin is connected with
>>> external Flash LED, and the control master is the sensor internal core.
>>> For turnning on the Flash LED, we should use I2C register access.
>>> So, I think it's exactly matches with hardware strobe as you metioned.
>>
>> Ok, I think I'm lost now. :-)
>>
>> What signals are sent from sensor to flash in both torch and flash cases?
> I guess the signal probably is just continuous repetition High/Low like PWM signal,
> which is generated by the core of sensor module.  Although I don't check what signal
> it is, it's very possible. Because it's the only way to be able to control intensity of  Flash.
> 
> So, I think the torch and flash case is the same way or signal in this case.

So... to summarise, the sensor determines the flash power by providing
the flash controller a pwm signal both in flash and torch modes, if I
understand correctly?

This sounds like a quite low level control. Is the flash controller
still an I2C device?

...

>>> So, I suggesst that, if we can not give to users(of course, this user
>>> want to use only flash function, not the camera) proper method usage
>>> (openning the videonode for using flash), let's express that the camera
>>> flash is used in the DEDICATED MODE now, as the enumeration name DEDICATED.
>>
>> No. The video nodes should not be involved since they are related to the
>> bridge (ISP) which is not needed to use the flash. Assuming that this is
>> the situation.
>>
>> This is how the use case should go:
>>
>> 1. open subdev node, e.g. /dev/v4l-subdev0, which is the flash
>> (flash controller powered on)
>> 2. VIDIOC_S_CTRL: V4L2_CID_FLASH_LED_MODE, V4L2_FLASH_LED_MODE_TORCH
>> (flash is on now)
>> 2. VIDIOC_S_CTRL: V4L2_CID_FLASH_LED_MODE, V4L2_FLASH_LED_MODE_NONE
>> (flash is off now)
>> 3. close the file handle
>> (flash controller powered off)
> Probably you mean media controller framework is based on. I get it. :)
> 
>>
>>> But, I think it might be not a big issue. So, any others don't comment at this,
>>> it's ok for me to pass this naming issue.
>>>
>>> I can see this API is very cool for camera man just like me.
>>
>> Thanks!
>>
>>> plus: actually I have the one of N-series, N810. So, the omap3isp is available to
>>> activate this device, not even it's cpu is omap3? Just question.
>>
>> The N810 has OMAP 2420 which has a completely different camera bridge,
>> and there's no flash. The drivers for the camera in N810 are omap24xxcam
>> and tcm825x. The drivers are functional in mainline but the platform
>> data is missing, as well as the CBUS driver. This work is queued but
>> unknown when there's time for this.
> Thanks for plus reply. I've tested tony's patch for booting the ubuntu long time ago,
> but I'm sure this gadget is good device. 

I've never tried it out with Ubuntu. Probably that 128 MiB of RAM is
slightly small for Ubuntu. ;-)

-- 
Sakari Ailus
sakari.ailus@maxwell.research.nokia.com