[RFC 0/2] BCM283x Camera Receiver driver

[Dave Stevenson]

On 15 June 2017 at 08:17, Hans Verkuil <hverkuil at xs4all.nl> wrote:
> On 06/14/2017 11:03 PM, Dave Stevenson wrote:
>>
>> On 14 June 2017 at 18:38, Hans Verkuil <hverkuil at xs4all.nl> wrote:
>>>
>>> On 06/14/2017 06:29 PM, Dave Stevenson wrote:
>>>>
>>>>
>>>> Hi Hans.
>>>>
>>>> On 14 June 2017 at 16:42, Hans Verkuil <hverkuil at xs4all.nl> wrote:
>>>>>
>>>>>
>>>>> Hi Dave,
>>>>>
>>>>> How does this driver relate to this staging driver:
>>>>>
>>>>> drivers/staging/vc04_services/bcm2835-camera/
>>>>>
>>>>> It's not obvious to me.
>>>>
>>>>
>>>>
>>>> drivers/staging/vc04_services/bcm2835-camera/ is using the VideoCore
>>>> firmware to control Unicam, ISP, and all the tuner algorithms. The ARM
>>>> gets delivered fully processed buffers from the VideoCore side. The
>>>> firmware only has drivers for the Omnivision OV5647 and Sony IMX219
>>>> (and an unsupported one for the Toshiba TC358743).
>>>>
>>>> This driver is solely the Unicam block, reading the data in over
>>>> CSI2/CCP2 from the sensor and writing it to memory. No ISP or control
>>>> loops.
>>>> Other than power management, this driver is running solely on the ARM
>>>> with no involvement from the VideoCore firmware.
>>>> The sensor driver is whatever suitable V4L2 subdevice driver you fancy
>>>> attaching (as long as it supports CSI2, or eventually CCP2).
>>>
>>>
>>>
>>> What is the interaction between these two drivers? Can they co-exist?
>>> I would expect them to be mutually exclusive.
>>
>>
>> Mutually exclusive for the same Unicam instance, yes.
>>
>> There are two Unicam instances on all BCM283x chips and both are
>> brought out on the Compute Modules. You could run bcm2835-unicam on
>> one and bcm2835-camera on the other if you so wished.
>> The firmware checks whether the csi nodes in the device tree are
>> active, and won't touch them if they are.
>
>
> It would be good if this explanation is mentioned both in the driver code
> and (I think) in the bindings document of *both* drivers. This setup is
> unusual, so some extra documentation isn't amiss.

OK, will add it to this driver for V2.
The other driver cleanups are on my to-do list. Would you object
horrendously if I deferred adding the explanation to that driver to
when I'm doing those cleanups?

> Regards,
>
>         Hans