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Message-ID: <4e9b8eb3-23c5-62ea-07dc-b51acb238dee@linuxfoundation.org>
Date: Fri, 9 Aug 2019 18:17:11 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: André Almeida <andrealmeid@...labora.com>,
mchehab@...nel.org, helen.koike@...labora.com, hverkuil@...all.nl,
laurent.pinchart@...asonboard.com
Cc: linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
skhan@...uxfoundation.org
Subject: Re: [PATCH 0/3] Collapse vimc into single monolithic driver
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
>
> ~# 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
> ...
>
>>
>> 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
>
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.
thanks,
-- Shuah
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