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    SubjectRe: [PATCH 0/3] Collapse vimc into single monolithic driver
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    On 8/9/19 9:51 PM, Helen Koike wrote:
    > Hi Andre,
    >
    > Thanks for testing this.
    >
    > On 8/9/19 9:24 PM, André Almeida wrote:
    >> On 8/9/19 9:17 PM, Shuah Khan wrote:
    >>> Hi Andre,
    >>>
    >>> On 8/9/19 5:52 PM, André Almeida wrote:
    >>>> Hello Shuah,
    >>>>
    >>>> Thanks for the patch, I did some comments below.
    >>>>
    >>>> On 8/9/19 6:45 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 emoves 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_ent_config global by moving it to vimc.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 third patch in the series fixes a general protection fault found
    >>>>> when rmmod is done while stream is active.
    >>>>
    >>>> I applied your patch on top of media_tree/master and I did some testing.
    >>>> Not sure if I did something wrong, but just adding and removing the
    >>>> module generated a kernel panic:
    >>>
    >>> Thanks for testing.
    >>>
    >>> Odd. I tested modprobe and rmmod both.I was working on Linux 5.3-rc2.
    >>> I will apply these to media latest and work from there. I have to
    >>> rebase these on top of the reverts from Lucas and Helen
    >>
    >> Ok, please let me know if I succeeded to reproduce.
    >>
    >>>>
    >>>> ~# modprobe vimc
    >>>> ~# rmmod vimc
    >>>> [   16.452974] stack segment: 0000 [#1] SMP PTI
    >>>> [   16.453688] CPU: 0 PID: 2038 Comm: rmmod Not tainted 5.3.0-rc2+ #36
    >>>> [   16.454678] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
    >>>> BIOS 1.12.0-20181126_142135-anatol 04/01/2014
    >>>> [   16.456191] RIP: 0010:kfree+0x4d/0x240
    >>>>
    >>>> <registers values...>
    >>>>
    >>>> [   16.469188] Call Trace:
    >>>> [   16.469666]  vimc_remove+0x35/0x90 [vimc]
    >>>> [   16.470436]  platform_drv_remove+0x1f/0x40
    >>>> [   16.471233]  device_release_driver_internal+0xd3/0x1b0
    >>>> [   16.472184]  driver_detach+0x37/0x6b
    >>>> [   16.472882]  bus_remove_driver+0x50/0xc1
    >>>> [   16.473569]  vimc_exit+0xc/0xca0 [vimc]
    >>>> [   16.474231]  __x64_sys_delete_module+0x18d/0x240
    >>>> [   16.475036]  do_syscall_64+0x43/0x110
    >>>> [   16.475656]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
    >>>> [   16.476504] RIP: 0033:0x7fceb8dafa4b
    >>>>
    >>>> <registers values...>
    >>>>
    >>>> [   16.484853] Modules linked in: vimc(-) videobuf2_vmalloc
    >>>> videobuf2_memops v4l2_tpg videobuf2_v4l2 videobuf2_common
    >>>> [   16.486187] ---[ end trace 91e5e0894e254d49 ]---
    >>>> [   16.486758] RIP: 0010:kfree+0x4d/0x240
    >>>>
    >>>> <registers values...>
    >>>>
    >>>> fish: “rmmod vimc” terminated by signal SIGSEGV (Address boundary error)
    >>>>
    >>>> I just added the module after booting, no other action was made. Here is
    >>>> how my `git log --oneline` looks like:
    >>>>
    >>>> 897d708e922b media: vimc: Fix gpf in rmmod path when stream is active
    >>>> 2e4a5ad8ad6d media: vimc: Collapse component structure into a single
    >>>> monolithic driver
    >>>> 7c8da1687e92 media: vimc: move private defines to a common header
    >>>> 97299a303532 media: Remove dev_err() usage after platform_get_irq()
    >>>> 25a3d6bac6b9 media: adv7511/cobalt: rename driver name to adv7511-v4l2
    >
    > I couldn't reproduce the error, my tree looks the same:
    >
    > [I] koike@floko ~/m/o/linux> git log --oneline
    > e3345155c8ed (HEAD) media: vimc: Fix gpf in rmmod path when stream is active
    > 43e9e2fe761f media: vimc: Collapse component structure into a single monolithic driver
    > 8a6d0b9adde0 media: vimc: move private defines to a common header
    > 97299a303532 (media/master) media: Remove dev_err() usage after platform_get_irq()
    > 25a3d6bac6b9 media: adv7511/cobalt: rename driver name to adv7511-v4l2

    Thanks Helen for trying to reproduce and sharing the result.
    >
    > André, is this deterministic? Or it just happens sometimes?
    >
    >>>> ...
    >>>>
    >>>>>
    >>>>> vimc_print_dot (--print-dot) topology after this change:
    >>>>> 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]
    >>>>> }
    >>>>
    >>>> Since the topology changed, it would be nice to change in the
    >>>> documentation as well. The current dot file can be found at
    >>>> `Documentation/media/v4l-drivers/vimc.dot` and it's rendered at this
    >>>> page: https://www.kernel.org/doc/html/latest/media/v4l-drivers/vimc.html
    >>>>
    >>>

    Thanks Andre! Yes this is the one I am using as a reference.

    >>> Topology shouldn't have changed. No changes to links or pads etc.
    >>> I will take a look to be sure. I agree that if topology changes
    >>> document should be updated.
    >>
    >> If you "diff" the current dot with the dot you generated, you will see
    >> some differences. The main difference is that "RGB/YUV Input" was a
    >> device "/dev/video2/", and now it a subdevice "/dev/v4l-subdev4".
    >
    > hmm, I just generated the topology for media/master, and it is
    > /dev/v4l-subdev4. As we don't have an implementation of the output device
    > yet, we used the sensor as a place holder and that is why it appears as
    > "/dev/v4l-subdev4", what is in the docs is the ideal version after we get
    > the output merged. We should update the docs in any case.
    >

    Helen! Does the master match what I generated. In any case, I will do
    the diff of before and after my patches for sure.

    I can update the document with what it should be.

    thanks,
    -- Shuah

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