Date:   Mon, 19 Aug 2019 12:00:22 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Helen Koike <helen.koike@...labora.com>, mchehab@...nel.org,
        hverkuil@...all.nl, laurent.pinchart@...asonboard.com,
        andrealmeid@...labora.com
Cc:     linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v2 0/2] Collapse vimc into single monolithic driver

On 8/16/19 2:03 PM, Helen Koike wrote:
> Hi Shuah,
> 
> Thanks for the patches.
> 
> On 8/15/19 4:42 PM, Shuah Khan wrote:
>> vimc uses Component API to split the driver into functional components.
>> The real hardware resembles a monolith structure than component and
>> component structure added a level of complexity making it hard to
>> maintain without adding any real benefit.
>>
>> The sensor is one vimc component that would makes sense to be a separate
>> module to closely align with the real hardware. It would be easier to
>> collapse vimc into single monolithic driver first and then split the
>> sensor off as a separate module.
>>
>> This patch series removes the component API and makes minimal changes to
>> the code base preserving the functional division of the code structure.
>> Preserving the functional structure allows us to split the sensor off
>> as a separate module in the future.
>>
>> Major design elements in this change are:
>>      - Use existing struct vimc_ent_config and struct vimc_pipeline_config
>>        to drive the initialization of the functional components.
>>      - Make vimc_device and vimc_ent_config global by moving them to
>>        vimc-common.h
>>      - Add two new hooks add and rm to initialize and register, unregister
>>        and free subdevs.
>>      - All component API is now gone and bind and unbind hooks are modified
>>        to do "add" and "rm" with minimal changes to just add and rm subdevs.
>>      - vimc-core's bind and unbind are now register and unregister.
>>      - vimc-core invokes "add" hooks from its vimc_register_devices().
>>        The "add" hooks remain the same and register subdevs. They don't
>>        create platform devices of their own and use vimc's pdev.dev as
>>        their reference device. The "add" hooks save their vimc_ent_device(s)
>>        in the corresponding vimc_ent_config.
>>      - vimc-core invokes "rm" hooks from its unregister to unregister
>>        subdevs and cleanup.
>>      - vimc-core invokes "add" and "rm" hooks with pointer to struct
>>        vimc_device and the corresponding struct vimc_ent_config pointer.
>>
>> The following configure and stream test works on all devices.
>>
>>      media-ctl -d platform:vimc -V '"Sensor A":0[fmt:SBGGR8_1X8/640x480]'
>>      media-ctl -d platform:vimc -V '"Debayer A":0[fmt:SBGGR8_1X8/640x480]'
>>      media-ctl -d platform:vimc -V '"Sensor B":0[fmt:SBGGR8_1X8/640x480]'
>>      media-ctl -d platform:vimc -V '"Debayer B":0[fmt:SBGGR8_1X8/640x480]'
>>
>>      v4l2-ctl -z platform:vimc -d "RGB/YUV Capture" -v width=1920,height=1440
>>      v4l2-ctl -z platform:vimc -d "Raw Capture 0" -v pixelformat=BA81
>>      v4l2-ctl -z platform:vimc -d "Raw Capture 1" -v pixelformat=BA81
>>
>>      v4l2-ctl --stream-mmap --stream-count=100 -d /dev/video1
>>      v4l2-ctl --stream-mmap --stream-count=100 -d /dev/video2
>>      v4l2-ctl --stream-mmap --stream-count=100 -d /dev/video3
>>
>> The second patch in the series fixes a general protection fault found
>> when rmmod is done while stream is active.
>>
>> - rmmod while streaming returns vimc is in use
>> - rmmod without active stream works correctly
>>
>> Changes since v1:
>> Patch 1 & 2: (patch 1 in this series)
>> - Collapsed the two patches into one
>> - Added common defines (vimc_device and vimc_ent_config) to vimc-common.h
>>    based on our discussion.
>> - Addressed review comments from Helen and Laurent
>> - Use vimc-common.h instead of creating a new file.
>> - Other minor comments from Helen on int vs. unsigned int and
>>    not needing to initialize ret in vimc_add_subdevs()
>> Patch 3 (patch 2 in this series):
>> - The second patch is the fix for gpf. Updated the patch after looking
>>    at the test results from Andre and Helen. This problem is in a common
>>    code and impacts all subdevs. The fix addresses the core problem and
>>    fixes it. Fix removes pads release from v4l2_device_unregister_subdev()
>>    and pads are now released from the sd release handler with all other
>>    resources.
>>
>> Outstanding:
>> - Update documentation with the correct topology.
>> - There is one outstanding gpf remaining in the unbind path. I will
>>    fix that in a separate patch. This is an existing problem and will
>>    be easier to fix on top of this patch series.
>>
>> vimc_print_dot (--print-dot) topology after this change: (no change
>> compared to media master)
>> digraph board {
>>          rankdir=TB
>>          n00000001 [label="{{} | Sensor A\n/dev/v4l-subdev0 | {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green]
>>          n00000001:port0 -> n00000005:port0 [style=bold]
>>          n00000001:port0 -> n0000000b [style=bold]
>>          n00000003 [label="{{} | Sensor B\n/dev/v4l-subdev1 | {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green]
>>          n00000003:port0 -> n00000008:port0 [style=bold]
>>          n00000003:port0 -> n0000000f [style=bold]
>>          n00000005 [label="{{<port0> 0} | Debayer A\n/dev/v4l-subdev2 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
>>          n00000005:port1 -> n00000015:port0
>>          n00000008 [label="{{<port0> 0} | Debayer B\n/dev/v4l-subdev3 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
>>          n00000008:port1 -> n00000015:port0 [style=dashed]
>>          n0000000b [label="Raw Capture 0\n/dev/video1", shape=box, style=filled, fillcolor=yellow]
>>          n0000000f [label="Raw Capture 1\n/dev/video2", shape=box, style=filled, fillcolor=yellow]
>>          n00000013 [label="{{} | RGB/YUV Input\n/dev/v4l-subdev4 | {<port0> 0}}", shape=Mrecord, style=filled, fillcolor=green]
>>          n00000013:port0 -> n00000015:port0 [style=dashed]
>>          n00000015 [label="{{<port0> 0} | Scaler\n/dev/v4l-subdev5 | {<port1> 1}}", shape=Mrecord, style=filled, fillcolor=green]
>>          n00000015:port1 -> n00000018 [style=bold]
>>          n00000018 [label="RGB/YUV Capture\n/dev/video3", shape=box, style=filled, fillcolor=yellow]
>>
>> Shuah Khan (2):
>>    media: vimc: Collapse component structure into a single monolithic
>>      driver
>>    media: vimc: Fix gpf in rmmod path when stream is active
> 
> I couldn't apply those on top of media/master, I think they are
> conflicting with the two "Reverts" commits in vimc.
> 

Sorry for the delay. I was out backpacking for a couple of days.

I knew I have to rebase after the reverts go in. I will do that
and address your comments on patch 1/2 and resend the series.

Thanks for the review. Your comments on naming make sense.

thanks,
-- Shuah

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