Re: [PATCH 0/3] Collapse vimc into single monolithic driver

From: AndrÃ Almeida
Date: Fri Aug 09 2019 - 19:53:48 EST

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In reply to: Shuah Khan: "[PATCH 3/3] media: vimc: Fix gpf in rmmod path when stream is active"
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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:

~# 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: ârmmod vimcâ 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
...

>
> 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,
AndrÃ

>
> Shuah Khan (3):
> media: vimc: move private defines to a common header
> media: vimc: Collapse component structure into a single monolithic
> driver
> media: vimc: Fix gpf in rmmod path when stream is active
>
> drivers/media/platform/vimc/Makefile | 7 +-
> drivers/media/platform/vimc/vimc-capture.c | 96 ++----------
> drivers/media/platform/vimc/vimc-common.c | 2 +-
> drivers/media/platform/vimc/vimc-core.c | 174 +++++++--------------
> drivers/media/platform/vimc/vimc-debayer.c | 84 ++--------
> drivers/media/platform/vimc/vimc-scaler.c | 83 ++--------
> drivers/media/platform/vimc/vimc-sensor.c | 82 ++--------
> drivers/media/platform/vimc/vimc.h | 121 ++++++++++++++
> 8 files changed, 230 insertions(+), 419 deletions(-)
> create mode 100644 drivers/media/platform/vimc/vimc.h
>

Next message: Dave Chinner: "Re: [RFC PATCH v2 01/19] fs/locks: Export F_LAYOUT lease to user space"
Previous message: Dave Chinner: "Re: [RFC PATCH v2 07/19] fs/xfs: Teach xfs to use new dax_layout_busy_page()"
In reply to: Shuah Khan: "[PATCH 3/3] media: vimc: Fix gpf in rmmod path when stream is active"
Next in thread: Shuah Khan: "Re: [PATCH 0/3] Collapse vimc into single monolithic driver"
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