soc-camera and focuser vcm devices
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Quoted 7 lines · Andrew Chew
Hello, Guennadi
I was wondering if you can provide some advice as to how focuser vcm devices would fit into the soc-camera framework. We have a raw sensor (an IMX219) with an AD5823 VCM (it's just a simple I2C device) to provide variable focus.
Quoted 6 lines
I currently have the sensor and camera host driver instantiated via device tree, following the guidelines in
Documentation/devicetree/bindings/media/video-interfaces.txt, by using theof_graphstuff, and that all works fine. However, I'm not sure what the proper way is to associate a focuser with that particular image pipeline, and I couldn't find any examples to draw from.
As discussed in an earlier thread [1], in principle soc-camera has support for attaching multiple subdevices to a camera-host (camera DMA engine) driver. In [2] you can see how I initially implemented DT for soc-camera, which also supported multiple subdevices. Beware, very old code. Some more comments are in [3].
Thanks
Guennadi
[1] http://www.spinics.net/lists/linux-sh/msg31436.html - see comment, following "Hm, I think, this isn't quite correct."
[2] http://marc.info/?l=linux-sh&m=134875489304837&w=1
[3] https://www.mail-archive.com/[email protected]/msg70514.html
Quoted 9 lines
Any help/guidance would be appreciated!
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Quoted 25 lines · Andrew Chew
Quoted 8 lines
Hello, Guennadi
I was wondering if you can provide some advice as to how focuser vcm devices would fit into the soc-camera framework. We have a raw sensor (an IMX219) with an AD5823 VCM (it's just a simple I2C device) to provide variable focus.
Quoted 6 lines
I currently have the sensor and camera host driver instantiated via device tree, following the guidelines in
Documentation/devicetree/bindings/media/video-interfaces.txt, by using theof_graphstuff, and that all works fine. However, I'm not sure what the proper way is to associate a focuser with that particular image pipeline, and I couldn't find any examples to draw from.As discussed in an earlier thread [1], in principle soc-camera has support for attaching multiple subdevices to a camera-host (camera DMA engine) driver. In [2] you can see how I initially implemented DT for soc-camera, which also supported multiple subdevices. Beware, very old code. Some more comments are in [3].
Thanks
Guennadi
Quoted 7 lines
[1] http://www.spinics.net/lists/linux-sh/msg31436.html - see comment, following "Hm, I think, this isn't quite correct."
[2] http://marc.info/?l=linux-sh&m=134875489304837&w=1
[3] https://www.mail-archive.com/linux-
[email protected]/msg70514.html
I think I get it, but just to clarify...currently, I'm going with the patch in [1], and I currently have multiple subdevs (sensors) hooked up and working with my soc-camera host driver. [2] was an alternate implementation, right? (as in, I don't need it).
So I understand that I can just hook up the focuser and flash subdevs to the camera host via device tree, in the same exact way of using the of_graph stuff to hook up the sensor subdev. My question is, is it then left up to the camera host driver to make sense of which subdevs do what? Or should/will there be a common mechanism to bind ports on a camera host to a sensor, focuser, and flash under a common group which makes up an image pipeline?
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Hi Andrew,
Quoted 28 lines · Andrew Chew
Quoted 28 lines · Andrew Chew
Quoted 8 lines
Hello, Guennadi
I was wondering if you can provide some advice as to how focuser vcm devices would fit into the soc-camera framework. We have a raw sensor (an IMX219) with an AD5823 VCM (it's just a simple I2C device) to provide variable focus.
Quoted 6 lines
I currently have the sensor and camera host driver instantiated via device tree, following the guidelines in
Documentation/devicetree/bindings/media/video-interfaces.txt, by using theof_graphstuff, and that all works fine. However, I'm not sure what the proper way is to associate a focuser with that particular image pipeline, and I couldn't find any examples to draw from.As discussed in an earlier thread [1], in principle soc-camera has support for attaching multiple subdevices to a camera-host (camera DMA engine) driver. In [2] you can see how I initially implemented DT for soc-camera, which also supported multiple subdevices. Beware, very old code. Some more comments are in [3].
Thanks
Guennadi[1] http://www.spinics.net/lists/linux-sh/msg31436.html - see comment, following "Hm, I think, this isn't quite correct."
Quoted 8 lines
Quoted 3 lines
[2] http://marc.info/?l=linux-sh&m=134875489304837&w=1
[3] https://www.mail-archive.com/[email protected]/msg70514.html
I think I get it, but just to clarify...currently, I'm going with the patch in [1], and I currently have multiple subdevs (sensors) hooked up and working with my soc-camera host driver. [2] was an alternate implementation, right? (as in, I don't need it).
No. [1] you don't need, it is already in the mainline, resp. its slightly updated version. I only quoted that thread for you above to read explanations about why that implementation didn't support multiple subdevices per host. To fix that support for multiple devices should be added to the current soc-camera mainline. To help with this task I quoted [2], which is my very early implementation attempt. [3] is just some more reading for general understanding.
Quoted 7 lines
So I understand that I can just hook up the focuser and flash subdevs to the camera host via device tree, in the same exact way of using the
of_graphstuff to hook up the sensor subdev. My question is, is it then left up to the camera host driver to make sense of which subdevs do what? Or should/will there be a common mechanism to bind ports on a camera host to a sensor, focuser, and flash under a common group which makes up an image pipeline?
Exactly, that's why you need multiple subdevices in groups, to have the whole pipeline probe only after all subdevices are available.
Thanks
Guennadi
Quoted 21 lines
Quoted 4 lines
I think I get it, but just to clarify...currently, I'm going with the patch in [1], and I currently have multiple subdevs (sensors) hooked up and working with my soc-camera host driver. [2] was an alternate implementation, right? (as in, I don't need it).
No. [1] you don't need, it is already in the mainline, resp. its slightly updated version. I only quoted that thread for you above to read explanations about why that implementation didn't support multiple subdevices per host. To fix that support for multiple devices should be added to the current soc-camera mainline. To help with this task I quoted [2], which is my very early implementation attempt. [3] is just some more reading for general understanding.
Quoted 7 lines
So I understand that I can just hook up the focuser and flash subdevs to the camera host via device tree, in the same exact way of using the
of_graphstuff to hook up the sensor subdev. My question is, is it then left up to the camera host driver to make sense of which subdevs do what? Or should/will there be a common mechanism to bind ports on a camera host to a sensor, focuser, and flash under a common group which makes up an image pipeline?
Quoted 2 lines
Exactly, that's why you need multiple subdevices in groups, to have the whole pipeline probe only after all subdevices are available.
Thanks, Guennadi. I think I'm still misunderstanding something, since I basically took [1], and am now (with a tiny modification of removing the hardcoded snippet of code that explicitly prevented multiple subdevs from getting probed) able to instantiate two sensors, both going through the camera host driver (i.e. I have /dev/video0 and /dev/video1 both able to capture from each sensor, going through the same camera host).
The part I don't understand is specifically how subdevs like focusers and flash devices are supposed to work. In examining the behavior of soc-camera more closely after I add my focuser subdev, it seems that there is this general assumption that all subdevs are image capture devices (because the subdev probe process finishes around soc_camera_probe_finish(), which tries (and fails with the focuser) to get supported capture formats.
But maybe I'm misunderstanding how focuser and flash devices are intended to be Implemented? I was under the impression that a focuser driver looks pretty much like a sensor driver (as in, it eventually calls v4l2_i2c_subdev_init() and v4l2_async_register_subdev(). In my case, the focuser's v4l2_async_register_subdev() call fails because soc_camera_probe_finish() failed its soc_camera_init_user_formats().
Soc_camera_init_user_formats() calls into the camera host driver's get_formats(), which tries to call the subdev's enum_mbus_fmt method. Of course, the focuser subdev doesn't implement this method, so it fails. Even if I changed the camera host driver so that it does something special with this subdev, the end result seems to me that we'll get a /dev/video2 for the focuser, which isn't the behavior we want (we want the focuser subdev to be available to the camera host, but it doesn't represent its own image capture entity).
So what is the proper thing to do with the focuser driver to get it somehow aggregated with a particular sensor subdev? Or is this something that the soc-camera framework doesn't define? I don't see any example focuser drivers to go by, so this is all new to me.
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