Asking advice for Camera/ISP driver framework design

Asking advice for Camera/ISP driver framework design

[Cliff Cai]

Dear guys,

I'm currently working on a camera/ISP Linux driver project.Of course,I
want it to be a V4L2 driver,but I got a problem about how to design
the driver framework.
let me introduce the background of this ISP(Image signal processor) a
little bit.
1.The ISP has two output paths,first one called main path which is
used to transfer image data for taking picture and recording,the other
one called preview path which is used to transfer image data for
previewing.
2.the two paths have the same image data input from sensor,but their
outputs are different,the output of main path is high quality and
larger image,while the output of preview path is smaller image.
3.the two output paths have independent DMA engines used to move image
data to system memory.

The problem is currently, the V4L2 framework seems only support one
buffer queue,and in my case,obviously,two buffer queues are required.
Any idea/advice for implementing such kind of V4L2 driver? or any
other better solutions?

Thanks a lot!
Cliff

Re: Asking advice for Camera/ISP driver framework design

[Scott Jiang]

2011/9/14 Cliff Cai <cliffcai.sh@gmail.com>:
> Dear guys,
>
> I'm currently working on a camera/ISP Linux driver project.Of course,I
> want it to be a V4L2 driver,but I got a problem about how to design
> the driver framework.
> let me introduce the background of this ISP(Image signal processor) a
> little bit.
> 1.The ISP has two output paths,first one called main path which is
> used to transfer image data for taking picture and recording,the other
> one called preview path which is used to transfer image data for
> previewing.
> 2.the two paths have the same image data input from sensor,but their
> outputs are different,the output of main path is high quality and
> larger image,while the output of preview path is smaller image.
> 3.the two output paths have independent DMA engines used to move image
> data to system memory.
>
> The problem is currently, the V4L2 framework seems only support one
> buffer queue,and in my case,obviously,two buffer queues are required.
> Any idea/advice for implementing such kind of V4L2 driver? or any
> other better solutions?
>
> Thanks a lot!
> Cliff
> --
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>
Your chip seems like davinci isp, only difference is dma. So you can
reference davinci drivers.
If dma interrupt doesn't happen at the same time,  I guess you must
wait because source image is the same.

Scott

Re: Asking advice for Camera/ISP driver framework design

[Laurent Pinchart]

Hi Cliff,

On Wednesday 14 September 2011 08:13:32 Cliff Cai wrote:
> Dear guys,
> 
> I'm currently working on a camera/ISP Linux driver project.Of course,I
> want it to be a V4L2 driver,but I got a problem about how to design
> the driver framework.
> let me introduce the background of this ISP(Image signal processor) a
> little bit.
> 1.The ISP has two output paths,first one called main path which is
> used to transfer image data for taking picture and recording,the other
> one called preview path which is used to transfer image data for
> previewing.
> 2.the two paths have the same image data input from sensor,but their
> outputs are different,the output of main path is high quality and
> larger image,while the output of preview path is smaller image.
> 3.the two output paths have independent DMA engines used to move image
> data to system memory.
> 
> The problem is currently, the V4L2 framework seems only support one
> buffer queue,and in my case,obviously,two buffer queues are required.
> Any idea/advice for implementing such kind of V4L2 driver? or any
> other better solutions?

Your driver should create two video nodes, one for each stream. They will each 
have their own buffers queue.

The driver should also implement the media controller API to let applications 
discover that the video nodes are related and how they interact with the ISP.

-- 
Regards,

Laurent Pinchart

Re: Asking advice for Camera/ISP driver framework design

[Cliff Cai]

On Thu, Sep 15, 2011 at 6:20 PM, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
> Hi Cliff,
>
> On Wednesday 14 September 2011 08:13:32 Cliff Cai wrote:
>> Dear guys,
>>
>> I'm currently working on a camera/ISP Linux driver project.Of course,I
>> want it to be a V4L2 driver,but I got a problem about how to design
>> the driver framework.
>> let me introduce the background of this ISP(Image signal processor) a
>> little bit.
>> 1.The ISP has two output paths,first one called main path which is
>> used to transfer image data for taking picture and recording,the other
>> one called preview path which is used to transfer image data for
>> previewing.
>> 2.the two paths have the same image data input from sensor,but their
>> outputs are different,the output of main path is high quality and
>> larger image,while the output of preview path is smaller image.
>> 3.the two output paths have independent DMA engines used to move image
>> data to system memory.
>>
>> The problem is currently, the V4L2 framework seems only support one
>> buffer queue,and in my case,obviously,two buffer queues are required.
>> Any idea/advice for implementing such kind of V4L2 driver? or any
>> other better solutions?
>
> Your driver should create two video nodes, one for each stream. They will each
> have their own buffers queue.
>
> The driver should also implement the media controller API to let applications
> discover that the video nodes are related and how they interact with the ISP.

Hi Laurent,

As "Documentation/media-framework" says, one of the goals of media
device model is "Discovering a device internal topology,and
configuring it at runtime".I'm just a bit confused about how
applications can discover the related video notes? Could you explain
it a little more?


Thanks a lot!
Cliff

Re: Asking advice for Camera/ISP driver framework design

[Sakari Ailus]

Cliff Cai wrote:
> On Thu, Sep 15, 2011 at 6:20 PM, Laurent Pinchart
> <laurent.pinchart@ideasonboard.com> wrote:
>> Hi Cliff,
>>
>> On Wednesday 14 September 2011 08:13:32 Cliff Cai wrote:
>>> Dear guys,
>>>
>>> I'm currently working on a camera/ISP Linux driver project.Of course,I
>>> want it to be a V4L2 driver,but I got a problem about how to design
>>> the driver framework.
>>> let me introduce the background of this ISP(Image signal processor) a
>>> little bit.
>>> 1.The ISP has two output paths,first one called main path which is
>>> used to transfer image data for taking picture and recording,the other
>>> one called preview path which is used to transfer image data for
>>> previewing.
>>> 2.the two paths have the same image data input from sensor,but their
>>> outputs are different,the output of main path is high quality and
>>> larger image,while the output of preview path is smaller image.
>>> 3.the two output paths have independent DMA engines used to move image
>>> data to system memory.
>>>
>>> The problem is currently, the V4L2 framework seems only support one
>>> buffer queue,and in my case,obviously,two buffer queues are required.
>>> Any idea/advice for implementing such kind of V4L2 driver? or any
>>> other better solutions?
>>
>> Your driver should create two video nodes, one for each stream. They will each
>> have their own buffers queue.
>>
>> The driver should also implement the media controller API to let applications
>> discover that the video nodes are related and how they interact with the ISP.
> 
> Hi Laurent,
> 
> As "Documentation/media-framework" says, one of the goals of media
> device model is "Discovering a device internal topology,and
> configuring it at runtime".I'm just a bit confused about how
> applications can discover the related video notes? Could you explain
> it a little more?

Hi Cliff,

The major and minor numbers of video nodes are provided to the user
space in struct media_entity_desc (defined in include/linux/media.h)
using MEDIA_IOC_ENUM_ENTITIES IOCTL. The major and minor numbers define
which device node corresponds to the video device; this isn't trivial
for an application to do so there's a library which makes it easier:

<URL:http://git.ideasonboard.org/?p=media-ctl.git;a=summary>

See src/media.h for the interface. An example how to use this is
available in src/main.c.

Entities the type of which is MEDIA_ENT_T_DEVNODE_V4L are V4L2 device nodes.

Regards,

-- 
Sakari Ailus
sakari.ailus@iki.fi

Re: Asking advice for Camera/ISP driver framework design

[Sakari Ailus]

Cliff Cai wrote:
> Dear guys,

Hi Cliff,

> I'm currently working on a camera/ISP Linux driver project.Of course,I
> want it to be a V4L2 driver,but I got a problem about how to design
> the driver framework.
> let me introduce the background of this ISP(Image signal processor) a
> little bit.
> 1.The ISP has two output paths,first one called main path which is
> used to transfer image data for taking picture and recording,the other
> one called preview path which is used to transfer image data for
> previewing.
> 2.the two paths have the same image data input from sensor,but their
> outputs are different,the output of main path is high quality and
> larger image,while the output of preview path is smaller image.

Is the ISP able to process images which already are in memory, or is
this only from the sensor?

> 3.the two output paths have independent DMA engines used to move image
> data to system memory.
> 
> The problem is currently, the V4L2 framework seems only support one
> buffer queue,and in my case,obviously,two buffer queues are required.
> Any idea/advice for implementing such kind of V4L2 driver? or any
> other better solutions?

Regards,

-- 
Sakari Ailus
sakari.ailus@iki.fi

Re: Asking advice for Camera/ISP driver framework design

[Cliff Cai]

On Fri, Sep 16, 2011 at 1:14 AM, Sakari Ailus <sakari.ailus@iki.fi> wrote:
> Cliff Cai wrote:
>> Dear guys,
>
> Hi Cliff,
>
>> I'm currently working on a camera/ISP Linux driver project.Of course,I
>> want it to be a V4L2 driver,but I got a problem about how to design
>> the driver framework.
>> let me introduce the background of this ISP(Image signal processor) a
>> little bit.
>> 1.The ISP has two output paths,first one called main path which is
>> used to transfer image data for taking picture and recording,the other
>> one called preview path which is used to transfer image data for
>> previewing.
>> 2.the two paths have the same image data input from sensor,but their
>> outputs are different,the output of main path is high quality and
>> larger image,while the output of preview path is smaller image.
>
> Is the ISP able to process images which already are in memory, or is
> this only from the sensor?

yes,it has another DMA to achieve  this.

Cliff

>> 3.the two output paths have independent DMA engines used to move image
>> data to system memory.
>>
>> The problem is currently, the V4L2 framework seems only support one
>> buffer queue,and in my case,obviously,two buffer queues are required.
>> Any idea/advice for implementing such kind of V4L2 driver? or any
>> other better solutions?
>
> Regards,
>
> --
> Sakari Ailus
> sakari.ailus@iki.fi
>

Re: Asking advice for Camera/ISP driver framework design

[Sakari Ailus]

On Fri, Sep 16, 2011 at 10:44:00AM +0800, Cliff Cai wrote:
> On Fri, Sep 16, 2011 at 1:14 AM, Sakari Ailus <sakari.ailus@iki.fi> wrote:
> > Cliff Cai wrote:
> >> Dear guys,
> >
> > Hi Cliff,
> >
> >> I'm currently working on a camera/ISP Linux driver project.Of course,I
> >> want it to be a V4L2 driver,but I got a problem about how to design
> >> the driver framework.
> >> let me introduce the background of this ISP(Image signal processor) a
> >> little bit.
> >> 1.The ISP has two output paths,first one called main path which is
> >> used to transfer image data for taking picture and recording,the other
> >> one called preview path which is used to transfer image data for
> >> previewing.
> >> 2.the two paths have the same image data input from sensor,but their
> >> outputs are different,the output of main path is high quality and
> >> larger image,while the output of preview path is smaller image.
> >
> > Is the ISP able to process images which already are in memory, or is
> > this only from the sensor?
> 
> yes,it has another DMA to achieve  this.

If you wish to support this, there would need to be an additional video
node.

What about the image processing performed by this ISP? Does it e.g. do
scaling or cropping? They also should be configured using the V4L2 subdev
interface. The OMAP 3 ISP is a good example of this; the technical reference
manual is publicly available and the driver is exemplary.

Your original message hints such functionality is available. It would be
very helpful to know what kind of processing (scaling, pixel format
conversion, crop, etc.) is supported by the ISP and what are the exact data
paths through it. That defines what the media device graph implemented by
the ISP driver should be. If you could show a graphical representation of
this, all the better.

Kind regards,

-- 
Sakari Ailus
e-mail: sakari.ailus@iki.fi	jabber/XMPP/Gmail: sailus@retiisi.org.uk

Re: Asking advice for Camera/ISP driver framework design

[Laurent Pinchart]

Hi Cliff,

On Thursday 15 September 2011 19:10:52 Sakari Ailus wrote:
> Cliff Cai wrote:
> > On Thu, Sep 15, 2011 at 6:20 PM, Laurent Pinchart wrote:
> >> On Wednesday 14 September 2011 08:13:32 Cliff Cai wrote:
> >>> Dear guys,
> >>> 
> >>> I'm currently working on a camera/ISP Linux driver project.Of course,I
> >>> want it to be a V4L2 driver,but I got a problem about how to design
> >>> the driver framework.
> >>> let me introduce the background of this ISP(Image signal processor) a
> >>> little bit.
> >>> 1.The ISP has two output paths,first one called main path which is
> >>> used to transfer image data for taking picture and recording,the other
> >>> one called preview path which is used to transfer image data for
> >>> previewing.
> >>> 2.the two paths have the same image data input from sensor,but their
> >>> outputs are different,the output of main path is high quality and
> >>> larger image,while the output of preview path is smaller image.
> >>> 3.the two output paths have independent DMA engines used to move image
> >>> data to system memory.
> >>> 
> >>> The problem is currently, the V4L2 framework seems only support one
> >>> buffer queue,and in my case,obviously,two buffer queues are required.
> >>> Any idea/advice for implementing such kind of V4L2 driver? or any
> >>> other better solutions?
> >> 
> >> Your driver should create two video nodes, one for each stream. They
> >> will each have their own buffers queue.
> >> 
> >> The driver should also implement the media controller API to let
> >> applications discover that the video nodes are related and how they
> >> interact with the ISP.
> > 
> > As "Documentation/media-framework" says, one of the goals of media
> > device model is "Discovering a device internal topology,and
> > configuring it at runtime".I'm just a bit confused about how
> > applications can discover the related video notes? Could you explain
> > it a little more?
> 
> The major and minor numbers of video nodes are provided to the user
> space in struct media_entity_desc (defined in include/linux/media.h)
> using MEDIA_IOC_ENUM_ENTITIES IOCTL. The major and minor numbers define
> which device node corresponds to the video device; this isn't trivial
> for an application to do so there's a library which makes it easier:
> 
> <URL:http://git.ideasonboard.org/?p=media-ctl.git;a=summary>
> 
> See src/media.h for the interface. An example how to use this is
> available in src/main.c.
> 
> Entities the type of which is MEDIA_ENT_T_DEVNODE_V4L are V4L2 device
> nodes.

http://www.ideasonboard.org/media/omap3isp.ps shows a device topology example 
generated automatically from the output of the media-ctl tool.

-- 
Regards,

Laurent Pinchart

Re: Asking advice for Camera/ISP driver framework design

[Hans Verkuil]

On Thursday, September 15, 2011 19:10:52 Sakari Ailus wrote:
> Cliff Cai wrote:
> > On Thu, Sep 15, 2011 at 6:20 PM, Laurent Pinchart
> > <laurent.pinchart@ideasonboard.com> wrote:
> >> Hi Cliff,
> >>
> >> On Wednesday 14 September 2011 08:13:32 Cliff Cai wrote:
> >>> Dear guys,
> >>>
> >>> I'm currently working on a camera/ISP Linux driver project.Of course,I
> >>> want it to be a V4L2 driver,but I got a problem about how to design
> >>> the driver framework.
> >>> let me introduce the background of this ISP(Image signal processor) a
> >>> little bit.
> >>> 1.The ISP has two output paths,first one called main path which is
> >>> used to transfer image data for taking picture and recording,the other
> >>> one called preview path which is used to transfer image data for
> >>> previewing.
> >>> 2.the two paths have the same image data input from sensor,but their
> >>> outputs are different,the output of main path is high quality and
> >>> larger image,while the output of preview path is smaller image.
> >>> 3.the two output paths have independent DMA engines used to move image
> >>> data to system memory.
> >>>
> >>> The problem is currently, the V4L2 framework seems only support one
> >>> buffer queue,and in my case,obviously,two buffer queues are required.
> >>> Any idea/advice for implementing such kind of V4L2 driver? or any
> >>> other better solutions?
> >>
> >> Your driver should create two video nodes, one for each stream. They will each
> >> have their own buffers queue.
> >>
> >> The driver should also implement the media controller API to let applications
> >> discover that the video nodes are related and how they interact with the ISP.
> > 
> > Hi Laurent,
> > 
> > As "Documentation/media-framework" says, one of the goals of media
> > device model is "Discovering a device internal topology,and
> > configuring it at runtime".I'm just a bit confused about how
> > applications can discover the related video notes? Could you explain
> > it a little more?
> 
> Hi Cliff,
> 
> The major and minor numbers of video nodes are provided to the user
> space in struct media_entity_desc (defined in include/linux/media.h)
> using MEDIA_IOC_ENUM_ENTITIES IOCTL. The major and minor numbers define
> which device node corresponds to the video device; this isn't trivial
> for an application to do so there's a library which makes it easier:
> 
> <URL:http://git.ideasonboard.org/?p=media-ctl.git;a=summary>

That reminds me: Laurent, this should really be moved to v4l-utils.git.
Any progress on that?

Regards,

	Hans

> 
> See src/media.h for the interface. An example how to use this is
> available in src/main.c.
> 
> Entities the type of which is MEDIA_ENT_T_DEVNODE_V4L are V4L2 device nodes.
> 
> Regards,
> 
> 

Re: Asking advice for Camera/ISP driver framework design

[Laurent Pinchart]

Hi Hans,

On Monday 26 September 2011 12:55:05 Hans Verkuil wrote:
> On Thursday, September 15, 2011 19:10:52 Sakari Ailus wrote:
> > Cliff Cai wrote:
> > > On Thu, Sep 15, 2011 at 6:20 PM, Laurent Pinchart wrote:
> > >> On Wednesday 14 September 2011 08:13:32 Cliff Cai wrote:
> > >>> Dear guys,
> > >>> 
> > >>> I'm currently working on a camera/ISP Linux driver project.Of
> > >>> course,I want it to be a V4L2 driver,but I got a problem about how
> > >>> to design the driver framework.
> > >>> let me introduce the background of this ISP(Image signal processor) a
> > >>> little bit.
> > >>> 1.The ISP has two output paths,first one called main path which is
> > >>> used to transfer image data for taking picture and recording,the
> > >>> other one called preview path which is used to transfer image data
> > >>> for previewing.
> > >>> 2.the two paths have the same image data input from sensor,but their
> > >>> outputs are different,the output of main path is high quality and
> > >>> larger image,while the output of preview path is smaller image.
> > >>> 3.the two output paths have independent DMA engines used to move
> > >>> image data to system memory.
> > >>> 
> > >>> The problem is currently, the V4L2 framework seems only support one
> > >>> buffer queue,and in my case,obviously,two buffer queues are required.
> > >>> Any idea/advice for implementing such kind of V4L2 driver? or any
> > >>> other better solutions?
> > >> 
> > >> Your driver should create two video nodes, one for each stream. They
> > >> will each have their own buffers queue.
> > >> 
> > >> The driver should also implement the media controller API to let
> > >> applications discover that the video nodes are related and how they
> > >> interact with the ISP.
> > > 
> > > Hi Laurent,
> > > 
> > > As "Documentation/media-framework" says, one of the goals of media
> > > device model is "Discovering a device internal topology,and
> > > configuring it at runtime".I'm just a bit confused about how
> > > applications can discover the related video notes? Could you explain
> > > it a little more?
> > 
> > Hi Cliff,
> > 
> > The major and minor numbers of video nodes are provided to the user
> > space in struct media_entity_desc (defined in include/linux/media.h)
> > using MEDIA_IOC_ENUM_ENTITIES IOCTL. The major and minor numbers define
> > which device node corresponds to the video device; this isn't trivial
> > for an application to do so there's a library which makes it easier:
> > 
> > <URL:http://git.ideasonboard.org/?p=media-ctl.git;a=summary>
> 
> That reminds me: Laurent, this should really be moved to v4l-utils.git.
> Any progress on that?

There are several pending patches for media-ctl that I want to apply first.

BTW, the MC API is not restricted to V4L devices. Wouldn't it be a bad signal 
for the MC API adoption to move media-ctl to v4l-utils ?

-- 
Regards,

Laurent Pinchart

Re: Asking advice for Camera/ISP driver framework design

[Hans Verkuil]

On Monday, September 26, 2011 18:03:16 Laurent Pinchart wrote:
> Hi Hans,
> 
> On Monday 26 September 2011 12:55:05 Hans Verkuil wrote:
> > On Thursday, September 15, 2011 19:10:52 Sakari Ailus wrote:
> > > Cliff Cai wrote:
> > > > On Thu, Sep 15, 2011 at 6:20 PM, Laurent Pinchart wrote:
> > > >> On Wednesday 14 September 2011 08:13:32 Cliff Cai wrote:
> > > >>> Dear guys,
> > > >>> 
> > > >>> I'm currently working on a camera/ISP Linux driver project.Of
> > > >>> course,I want it to be a V4L2 driver,but I got a problem about how
> > > >>> to design the driver framework.
> > > >>> let me introduce the background of this ISP(Image signal processor) a
> > > >>> little bit.
> > > >>> 1.The ISP has two output paths,first one called main path which is
> > > >>> used to transfer image data for taking picture and recording,the
> > > >>> other one called preview path which is used to transfer image data
> > > >>> for previewing.
> > > >>> 2.the two paths have the same image data input from sensor,but their
> > > >>> outputs are different,the output of main path is high quality and
> > > >>> larger image,while the output of preview path is smaller image.
> > > >>> 3.the two output paths have independent DMA engines used to move
> > > >>> image data to system memory.
> > > >>> 
> > > >>> The problem is currently, the V4L2 framework seems only support one
> > > >>> buffer queue,and in my case,obviously,two buffer queues are required.
> > > >>> Any idea/advice for implementing such kind of V4L2 driver? or any
> > > >>> other better solutions?
> > > >> 
> > > >> Your driver should create two video nodes, one for each stream. They
> > > >> will each have their own buffers queue.
> > > >> 
> > > >> The driver should also implement the media controller API to let
> > > >> applications discover that the video nodes are related and how they
> > > >> interact with the ISP.
> > > > 
> > > > Hi Laurent,
> > > > 
> > > > As "Documentation/media-framework" says, one of the goals of media
> > > > device model is "Discovering a device internal topology,and
> > > > configuring it at runtime".I'm just a bit confused about how
> > > > applications can discover the related video notes? Could you explain
> > > > it a little more?
> > > 
> > > Hi Cliff,
> > > 
> > > The major and minor numbers of video nodes are provided to the user
> > > space in struct media_entity_desc (defined in include/linux/media.h)
> > > using MEDIA_IOC_ENUM_ENTITIES IOCTL. The major and minor numbers define
> > > which device node corresponds to the video device; this isn't trivial
> > > for an application to do so there's a library which makes it easier:
> > > 
> > > <URL:http://git.ideasonboard.org/?p=media-ctl.git;a=summary>
> > 
> > That reminds me: Laurent, this should really be moved to v4l-utils.git.
> > Any progress on that?
> 
> There are several pending patches for media-ctl that I want to apply first.
> 
> BTW, the MC API is not restricted to V4L devices. Wouldn't it be a bad signal 
> for the MC API adoption to move media-ctl to v4l-utils ?

Right now the MC is primarily used by V4L, so I think a public git repo on
linuxtv.org is a better place for it. Perhaps called media-utils.git.

Actually, what I would like to see is that the V4L, DVB and media utilities
are all combined in one git repository. They are all closely related IMO.

Regards,

	Hans