Re: [PATCH v6 22/24] drm/amdgpu: Provide ddc symlink in connector sysfs directory

Re: [PATCH v6 22/24] drm/amdgpu: Provide ddc symlink in connector sysfs directory

[Andrzej Pietrasiewicz]

Hi Alex,


W dniu 26.07.2019 o 21:28, Alex Deucher pisze:
> On Fri, Jul 26, 2019 at 1:28 PM Andrzej Pietrasiewicz
> <andrzej.p@collabora.com> wrote:
>>
>> Use the ddc pointer provided by the generic connector.
>>
>> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> 
> Note that this only covers the legacy display code.  The new DC
> display code also needs to be converted.  See:
> drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c

In amdgpu_dm_connector_init() the ddc is &i2c->base, is it?

But it is not clear to me how can I find ddc pointer in
dm_dp_add_mst_connector()?

Andrzej


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Re: [PATCH v6 22/24] drm/amdgpu: Provide ddc symlink in connector sysfs directory

[Alex Deucher]

On Fri, Jul 26, 2019 at 3:42 PM Andrzej Pietrasiewicz
<andrzej.p@collabora.com> wrote:
>
> Hi Alex,
>
>
> W dniu 26.07.2019 o 21:28, Alex Deucher pisze:
> > On Fri, Jul 26, 2019 at 1:28 PM Andrzej Pietrasiewicz
> > <andrzej.p@collabora.com> wrote:
> >>
> >> Use the ddc pointer provided by the generic connector.
> >>
> >> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> >
> > Note that this only covers the legacy display code.  The new DC
> > display code also needs to be converted.  See:
> > drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
>
> In amdgpu_dm_connector_init() the ddc is &i2c->base, is it?

Yes.

>
> But it is not clear to me how can I find ddc pointer in
> dm_dp_add_mst_connector()?

+ Harry and Nick.

hmmm, not sure about MST.  Maybe just skip them for now.

Alex

>
> Andrzej
>

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Re: Review required [Was: Associate ddc adapters with connectors]

[Neil Armstrong]

Hi Sam,

On 26/07/2019 20:55, Sam Ravnborg wrote:
> Hi all.
> 
> Andrzej have done a good job following up on feedback and this series is
> now ready.
> 
> We need ack on the patches touching the individual drivers before we can
> proceed.
> Please check your drivers and get back.

I can apply all core and maintainer-acked patches for now :
1, 2, 7, 10, 11, 16, 17, 18, 19, 20, 21, 22, 23

and Andrzej can resend not applied patches with Yours and Emil's Reviewed-by,
so we can wait a few more days to apply them.

Neil

> 
> 	Sam
> 
>> Hi Andezej.
>>
>> On Fri, Jul 26, 2019 at 07:22:54PM +0200, Andrzej Pietrasiewicz wrote:
>>> It is difficult for a user to know which of the i2c adapters is for which
>>> drm connector. This series addresses this problem.
>>>
>>> The idea is to have a symbolic link in connector's sysfs directory, e.g.:
>>>
>>> ls -l /sys/class/drm/card0-HDMI-A-1/ddc
>>> lrwxrwxrwx 1 root root 0 Jun 24 10:42 /sys/class/drm/card0-HDMI-A-1/ddc \
>>> 	-> ../../../../soc/13880000.i2c/i2c-2
>>>
>>> The user then knows that their card0-HDMI-A-1 uses i2c-2 and can e.g. run
>>> ddcutil:
>>>
>>> ddcutil -b 2 getvcp 0x10
>>> VCP code 0x10 (Brightness): current value =    90, max value =   100
>>>
>>> The first patch in the series adds struct i2c_adapter pointer to struct
>>> drm_connector. If the field is used by a particular driver, then an
>>> appropriate symbolic link is created by the generic code, which is also added
>>> by this patch.
>>>
>>> Patch 2 adds a new variant of drm_connector_init(), see the changelog
>>> below.
>>>
>>> Patches 3..24 are examples of how to convert a driver to this new scheme.
>>>
>> ...
>>>
>>> v5..v6:
>>>
>>> - improved subject line of patch 1
>>> - added kernel-doc for drm_connector_init_with_ddc()
>>> - improved kernel-doc for the ddc field of struct drm_connector
>>> - added Reviewed-by in patches 17 and 18
>>> - added Acked-by in patch 2
>>> - made the ownership of ddc i2c_adapter explicit in all patches,
>>> this made the affected patches much simpler
>>
>> Looks good now.
>> Patch 1 and 2 are:
>> Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
>>
>> The remaining patches are:
>> Acked-by: Sam Ravnborg <sam@ravnborg.org>
>>
>> 	Sam
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel


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Re: Review required [Was: Associate ddc adapters with connectors]

[Sam Ravnborg]

Hi Neil.

On Wed, Jul 31, 2019 at 10:00:14AM +0200, Neil Armstrong wrote:
> Hi Sam,
> 
> On 26/07/2019 20:55, Sam Ravnborg wrote:
> > Hi all.
> > 
> > Andrzej have done a good job following up on feedback and this series is
> > now ready.
> > 
> > We need ack on the patches touching the individual drivers before we can
> > proceed.
> > Please check your drivers and get back.
> 
> I can apply all core and maintainer-acked patches for now :
> 1, 2, 7, 10, 11, 16, 17, 18, 19, 20, 21, 22, 23
> 
> and Andrzej can resend not applied patches with Yours and Emil's Reviewed-by,
> so we can wait a few more days to apply them.

Sounds like a good plan.
Thanks for thaking care of this.

	Sam

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Re: Review required [Was: Associate ddc adapters with connectors]

[Andrzej Pietrasiewicz]

W dniu 31.07.2019 o 12:40, Sam Ravnborg pisze:
> Hi Neil.
> 
> On Wed, Jul 31, 2019 at 10:00:14AM +0200, Neil Armstrong wrote:
>> Hi Sam,
>>
>> On 26/07/2019 20:55, Sam Ravnborg wrote:
>>> Hi all.
>>>
>>> Andrzej have done a good job following up on feedback and this series is
>>> now ready.
>>>
>>> We need ack on the patches touching the individual drivers before we can
>>> proceed.
>>> Please check your drivers and get back.
>>
>> I can apply all core and maintainer-acked patches for now :
>> 1, 2, 7, 10, 11, 16, 17, 18, 19, 20, 21, 22, 23
>>
>> and Andrzej can resend not applied patches with Yours and Emil's Reviewed-by,
>> so we can wait a few more days to apply them.
> 
> Sounds like a good plan.
> Thanks for thaking care of this.

When is it good time to resend patches 3, 4, 5, 6, 8, 9, 12, 13, 14, 15, 24 as a
new series?

Andrzej

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Re: Review required [Was: Associate ddc adapters with connectors]

[Neil Armstrong]

On 31/07/2019 15:10, Andrzej Pietrasiewicz wrote:
> W dniu 31.07.2019 o 12:40, Sam Ravnborg pisze:
>> Hi Neil.
>>
>> On Wed, Jul 31, 2019 at 10:00:14AM +0200, Neil Armstrong wrote:
>>> Hi Sam,
>>>
>>> On 26/07/2019 20:55, Sam Ravnborg wrote:
>>>> Hi all.
>>>>
>>>> Andrzej have done a good job following up on feedback and this series is
>>>> now ready.
>>>>
>>>> We need ack on the patches touching the individual drivers before we can
>>>> proceed.
>>>> Please check your drivers and get back.
>>>
>>> I can apply all core and maintainer-acked patches for now :
>>> 1, 2, 7, 10, 11, 16, 17, 18, 19, 20, 21, 22, 23
>>>
>>> and Andrzej can resend not applied patches with Yours and Emil's Reviewed-by,
>>> so we can wait a few more days to apply them.
>>
>> Sounds like a good plan.
>> Thanks for thaking care of this.
> 
> When is it good time to resend patches 3, 4, 5, 6, 8, 9, 12, 13, 14, 15, 24 as a
> new series?

I'll ping you when everything is applied, build-tested and pushed on drm-misc-next

Neil

> 
> Andrzej


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Re: Review required [Was: Associate ddc adapters with connectors]

[Neil Armstrong]

Hi Andrzej,

On 31/07/2019 16:22, Neil Armstrong wrote:
> On 31/07/2019 15:10, Andrzej Pietrasiewicz wrote:
>> W dniu 31.07.2019 o 12:40, Sam Ravnborg pisze:
>>> Hi Neil.
>>>
>>> On Wed, Jul 31, 2019 at 10:00:14AM +0200, Neil Armstrong wrote:
>>>> Hi Sam,
>>>>
>>>> On 26/07/2019 20:55, Sam Ravnborg wrote:
>>>>> Hi all.
>>>>>
>>>>> Andrzej have done a good job following up on feedback and this series is
>>>>> now ready.
>>>>>
>>>>> We need ack on the patches touching the individual drivers before we can
>>>>> proceed.
>>>>> Please check your drivers and get back.
>>>>
>>>> I can apply all core and maintainer-acked patches for now :
>>>> 1, 2, 7, 10, 11, 16, 17, 18, 19, 20, 21, 22, 23
>>>>
>>>> and Andrzej can resend not applied patches with Yours and Emil's Reviewed-by,
>>>> so we can wait a few more days to apply them.
>>>
>>> Sounds like a good plan.
>>> Thanks for thaking care of this.
>>
>> When is it good time to resend patches 3, 4, 5, 6, 8, 9, 12, 13, 14, 15, 24 as a
>> new series?
> 
> I'll ping you when everything is applied, build-tested and pushed on drm-misc-next

I pushed 1, 2, 7, 10, 11, 16, 17, 18, 19, 20, 21, 22, 23 :
bed7a2182de6 drm/radeon: Provide ddc symlink in connector sysfs directory
5b50fa2b35a4 drm/amdgpu: Provide ddc symlink in connector sysfs directory
cfb444552926 drm/bridge: ti-tfp410: Provide ddc symlink in connector sysfs directory
9ebc4d2140ad drm/bridge: dw-hdmi: Provide ddc symlink in connector sysfs directory
a4f9087e85de drm/bridge: dumb-vga-dac: Provide ddc symlink in connector sysfs directory
350fd554ee44 drm/ast: Provide ddc symlink in connector sysfs directory
9572ae176a10 drm/mgag200: Provide ddc symlink in connector sysfs directory
7058e76682d7 drm: sti: Provide ddc symlink in hdmi connector sysfs directory
2ae7eb372ed4 drm/imx: imx-tve: Provide ddc symlink in connector's sysfs
be0ec35940bc drm/imx: imx-ldb: Provide ddc symlink in connector's sysfs
1e8f17855ff8 drm/sun4i: hdmi: Provide ddc symlink in sun4i hdmi connector sysfs directory
100163df4203 drm: Add drm_connector_init() variant with ddc
e1a29c6c5955 drm: Add ddc link in sysfs created by drm_connector

Neil

> 
> Neil
> 
>>
>> Andrzej
> 


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Re: [PATCH 02/13] drm/radeon: Eliminate possible use of an uninitialized variable

[Neil Armstrong]

Hi Andrzej,

I had to revert the previous patch, so you should re-spin it entirely :

================================
After merging the drm-misc tree, today's linux-next build (x86_64
allmodconfig) failed like this:

drivers/gpu/drm/radeon/radeon_connectors.c: In function 'radeon_add_legacy_connector':
drivers/gpu/drm/radeon/radeon_connectors.c:2433:5: error: 'ddc' undeclared (first use in this function)
     ddc = &radeon_connector->ddc_bus->adapter;
     ^~~
drivers/gpu/drm/radeon/radeon_connectors.c:2433:5: note: each undeclared identifier is reported only once for each function it appears in

Caused by commit

  bed7a2182de6 ("drm/radeon: Provide ddc symlink in connector sysfs directory")

I have used the drm-misc tree from next-20190731 for today.
==================================

Neil

On 31/07/2019 18:58, Andrzej Pietrasiewicz wrote:
> ddc local variable is passed to drm_connector_init_with_ddc() and should
> be NULL if no ddc is available.
> 
> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> ---
>  drivers/gpu/drm/radeon/radeon_connectors.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/radeon/radeon_connectors.c b/drivers/gpu/drm/radeon/radeon_connectors.c
> index b3ad8d890801..d11131d03ed6 100644
> --- a/drivers/gpu/drm/radeon/radeon_connectors.c
> +++ b/drivers/gpu/drm/radeon/radeon_connectors.c
> @@ -1870,7 +1870,7 @@ radeon_add_atom_connector(struct drm_device *dev,
>  	struct radeon_connector_atom_dig *radeon_dig_connector;
>  	struct drm_encoder *encoder;
>  	struct radeon_encoder *radeon_encoder;
> -	struct i2c_adapter *ddc;
> +	struct i2c_adapter *ddc = NULL;
>  	uint32_t subpixel_order = SubPixelNone;
>  	bool shared_ddc = false;
>  	bool is_dp_bridge = false;
> 


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Re: [PATCH 05/13] drm: rockchip: Provide ddc symlink in inno_hdmi sysfs directory

[Heiko Stuebner]

Am Mittwoch, 31. Juli 2019, 18:58:14 CEST schrieb Andrzej Pietrasiewicz:
> Use the ddc pointer provided by the generic connector.
> 
> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> Acked-by: Sam Ravnborg <sam@ravnborg.org>
> Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

Acked-by: Heiko Stuebner <heiko@sntech.de>





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Re: [PATCH 04/13] drm: rockchip: Provide ddc symlink in rk3066_hdmi sysfs directory

[Heiko Stuebner]

Am Mittwoch, 31. Juli 2019, 18:58:13 CEST schrieb Andrzej Pietrasiewicz:
> Use the ddc pointer provided by the generic connector.
> 
> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> Acked-by: Sam Ravnborg <sam@ravnborg.org>
> Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

Acked-by: Heiko Stuebner <heiko@sntech.de>




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Re: [PATCH v6 19/24] drm/bridge: dumb-vga-dac: Provide ddc symlink in connector sysfs directory

[Guenter Roeck]

On Fri, Jul 26, 2019 at 07:23:13PM +0200, Andrzej Pietrasiewicz wrote:
> Use the ddc pointer provided by the generic connector.
> 
> Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>

This patch results in a crash when running qemu:versatilepb.

Unable to handle kernel NULL pointer dereference at virtual address 000000c5
pgd = (ptrval)
[000000c5] *pgd=00000000
Internal error: Oops: 5 [#1] ARM
Modules linked in:
CPU: 0 PID: 1 Comm: swapper Not tainted 5.3.0-rc1+ #1
Hardware name: ARM-Versatile (Device Tree Support)
PC is at sysfs_do_create_link_sd+0x38/0xd8
LR is at sysfs_do_create_link_sd+0x38/0xd8
pc : [<c01ac94c>]    lr : [<c01ac94c>]    psr: a0000153
sp : c783bd18  ip : 00000000  fp : c783bde8
r10: c7ef5ea8  r9 : 00000001  r8 : c0955dc0
r7 : c73cb5b0  r6 : c73cd800  r5 : 000000ad  r4 : 00000000
r3 : c7838ae0  r2 : 00000000  r1 : 00000008  r0 : c0aa2898
Flags: NzCv  IRQs on  FIQs off  Mode SVC_32  ISA ARM  Segment none
Control: 00093177  Table: 00004000  DAC: 00000053
Process swapper (pid: 1, stack limit = 0x(ptrval))
Stack: (0xc783bd18 to 0xc783c000)
bd00:                                                       c73ccc48 c73ccc74
bd20: c73cd800 c0ac7c88 00000000 c729cc80 c7ef5ea8 c04c7fc0 c73ccc48 c0a73068
bd40: c73cd800 c0ac7c88 00000000 c04c87e0 00000001 00000000 c04cefcc c04dc3f8
bd60: c73a9030 c73cd800 c73ccc48 7fc2ce37 00000000 c73cd800 00000000 c04cefcc
bd80: c73cd800 00000000 00000000 c04b4ebc c0a73068 c7ef5ea8 c783bde8 c049ffcc
bda0: c73a9020 c73cd800 c78e6000 c73a9020 00000000 c73a9020 c0a73068 c04df2f8
bdc0: c783bde8 c095a76c c73a9020 c0065744 c73ccc20 c73a9020 00000000 00000001
bde0: c7838ae0 00000000 c73ccc20 7fc2ce37 00000000 c78e6000 00000000 c0ac7c34
be00: c07dc1f8 00000000 00000000 c0a6b384 c0a59858 c045e8d8 c78e6000 c1173a78
be20: 00000000 c0ac7c34 00000000 c04e77c4 c78e6000 c0ac7c34 c0ac7c34 c0a73068
be40: 00000000 ffffe000 c0a6b384 c04e7a34 c0ac7c34 c0ac7c34 c0a73068 c78e6000
be60: 00000000 c0ac7c34 c0a73068 00000000 ffffe000 c0a6b384 c0a59858 c04e7cf0
be80: 00000000 c0ac7c34 c78e6000 c04e7d7c 00000000 c0ac7c34 c04e7cf8 c04e5928
bea0: c73b2800 c78d88a0 c78dd110 7fc2ce37 ffffe000 c0ac7c34 c73b2800 c0ac16e0
bec0: 00000000 c04e6b28 c095a73c c0af0a60 c0a73068 c0ac7c34 c0af0a60 c0a73068
bee0: c0a401c4 c04e8968 ffffe000 c0af0a60 c0a73068 c000b3bc 00000115 00000000
bf00: c7ffce6c c7ffce00 c09e15b0 00000115 00000115 c0048844 c09e000c c097cfd4
bf20: 00000000 00000006 00000006 00000000 00000000 c7ffce6c ffffe000 c006954c
bf40: ffffe000 7fc2ce37 c0afb000 c0af0a60 00000115 c0afb000 00000007 c0a59850
bf60: ffffe000 c0a111e8 00000006 00000006 00000000 c0a10678 00000000 7fc2ce37
bf80: 00000000 00000000 c07824cc 00000000 00000000 00000000 00000000 00000000
bfa0: 00000000 c07824d4 00000000 c00090b0 00000000 00000000 00000000 00000000
bfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
bfe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
[<c01ac94c>] (sysfs_do_create_link_sd) from [<c04c7fc0>] (drm_connector_register.part.1+0x40/0xa0)
[<c04c7fc0>] (drm_connector_register.part.1) from [<c04c87e0>] (drm_connector_register_all+0x90/0xb8)
[<c04c87e0>] (drm_connector_register_all) from [<c04cefcc>] (drm_modeset_register_all+0x44/0x6c)
[<c04cefcc>] (drm_modeset_register_all) from [<c04b4ebc>] (drm_dev_register+0x15c/0x1c0)
[<c04b4ebc>] (drm_dev_register) from [<c04df2f8>] (pl111_amba_probe+0x2e0/0x4ac)
[<c04df2f8>] (pl111_amba_probe) from [<c045e8d8>] (amba_probe+0x9c/0x118)
[<c045e8d8>] (amba_probe) from [<c04e77c4>] (really_probe+0x1c0/0x2bc)
[<c04e77c4>] (really_probe) from [<c04e7a34>] (driver_probe_device+0x5c/0x170)
[<c04e7a34>] (driver_probe_device) from [<c04e7cf0>] (device_driver_attach+0x58/0x60)
[<c04e7cf0>] (device_driver_attach) from [<c04e7d7c>] (__driver_attach+0x84/0xc0)
[<c04e7d7c>] (__driver_attach) from [<c04e5928>] (bus_for_each_dev+0x70/0xb4)
[<c04e5928>] (bus_for_each_dev) from [<c04e6b28>] (bus_add_driver+0x154/0x1e0)
[<c04e6b28>] (bus_add_driver) from [<c04e8968>] (driver_register+0x74/0x108)
[<c04e8968>] (driver_register) from [<c000b3bc>] (do_one_initcall+0x84/0x2e4)
[<c000b3bc>] (do_one_initcall) from [<c0a111e8>] (kernel_init_freeable+0x2bc/0x394)
[<c0a111e8>] (kernel_init_freeable) from [<c07824d4>] (kernel_init+0x8/0xf0)
[<c07824d4>] (kernel_init) from [<c00090b0>] (ret_from_fork+0x14/0x24)
Exception stack(0xc783bfb0 to 0xc783bff8)
bfa0:                                     00000000 00000000 00000000 00000000
bfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
bfe0: 00000000 00000000 00000000 00000000 00000013 00000000
Code: e59f00a0 e1a09003 e1a08002 eb176e54 (e5955018) 
---[ end trace f503b374936886c5 ]---

Bisect log attached.

Guenter

---
# bad: [3880be629e26f6c407593602398c6651860d5fae] Add linux-next specific files for 20190807
# good: [e21a712a9685488f5ce80495b37b9fdbe96c230d] Linux 5.3-rc3
git bisect start 'HEAD' 'v5.3-rc3'
# good: [83d74da9e6d2ca78b32e9e794c6bcbd433d5efaa] Merge remote-tracking branch 'crypto/master'
git bisect good 83d74da9e6d2ca78b32e9e794c6bcbd433d5efaa
# bad: [3add021bff629f1792a5e4268afe13b3047b5523] Merge remote-tracking branch 'sound/for-next'
git bisect bad 3add021bff629f1792a5e4268afe13b3047b5523
# good: [4ef58ee18a654b1992d00281501d6eff051a0c5e] Merge remote-tracking branch 'amdgpu/drm-next'
git bisect good 4ef58ee18a654b1992d00281501d6eff051a0c5e
# good: [f729d8d9628d4093675abfd62d8d3a06d3d11732] drm/tinydrm: Move tinydrm_machine_little_endian()
git bisect good f729d8d9628d4093675abfd62d8d3a06d3d11732
# bad: [178e5f3a5bc1d67d1248a74c0abab41040abe7c4] drm/crc-debugfs: Add notes about CRC<->commit interactions
git bisect bad 178e5f3a5bc1d67d1248a74c0abab41040abe7c4
# good: [0486ad20e73d03c82208b802ac41e80b942b23f6] drm/rockchip: Make analogix_dp_atomic_check static
git bisect good 0486ad20e73d03c82208b802ac41e80b942b23f6
# bad: [92cb3e5980638a37c56091e605aa837d0af05a9d] dma-buf: fix stack corruption in dma_fence_chain_release
git bisect bad 92cb3e5980638a37c56091e605aa837d0af05a9d
# good: [350fd554ee44325661d0d3c3831f428f4fbb0f2d] drm/ast: Provide ddc symlink in connector sysfs directory
git bisect good 350fd554ee44325661d0d3c3831f428f4fbb0f2d
# bad: [28ba1b1da49a20ba8fb767d6ddd7c521ec79a119] drm: mali-dp: Mark expected switch fall-through
git bisect bad 28ba1b1da49a20ba8fb767d6ddd7c521ec79a119
# bad: [5b50fa2b35a4ddad11cb3d06231bf71759b49566] drm/amdgpu: Provide ddc symlink in connector sysfs directory
git bisect bad 5b50fa2b35a4ddad11cb3d06231bf71759b49566
# bad: [9ebc4d2140adcdea2399b42d3f0d2f7e141ac1a8] drm/bridge: dw-hdmi: Provide ddc symlink in connector sysfs directory
git bisect bad 9ebc4d2140adcdea2399b42d3f0d2f7e141ac1a8
# bad: [a4f9087e85de141e4e6d21ac2c583ae096cc9aba] drm/bridge: dumb-vga-dac: Provide ddc symlink in connector sysfs directory
git bisect bad a4f9087e85de141e4e6d21ac2c583ae096cc9aba
# first bad commit: [a4f9087e85de141e4e6d21ac2c583ae096cc9aba] drm/bridge: dumb-vga-dac: Provide ddc symlink in connector sysfs directory

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Re: [PATCH v6 19/24] drm/bridge: dumb-vga-dac: Provide ddc symlink in connector sysfs directory

[Geert Uytterhoeven]

Hi Günter,

On Thu, Aug 8, 2019 at 5:42 AM Guenter Roeck <linux@roeck-us.net> wrote:
> On Fri, Jul 26, 2019 at 07:23:13PM +0200, Andrzej Pietrasiewicz wrote:
> > Use the ddc pointer provided by the generic connector.
> >
> > Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
> > Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
>
> This patch results in a crash when running qemu:versatilepb.
>
> Unable to handle kernel NULL pointer dereference at virtual address 000000c5
> pgd = (ptrval)
> [000000c5] *pgd=00000000
> Internal error: Oops: 5 [#1] ARM
> Modules linked in:
> CPU: 0 PID: 1 Comm: swapper Not tainted 5.3.0-rc1+ #1
> Hardware name: ARM-Versatile (Device Tree Support)
> PC is at sysfs_do_create_link_sd+0x38/0xd8
> LR is at sysfs_do_create_link_sd+0x38/0xd8

> [<c01ac94c>] (sysfs_do_create_link_sd) from [<c04c7fc0>] (drm_connector_register.part.1+0x40/0xa0)
> [<c04c7fc0>] (drm_connector_register.part.1) from [<c04c87e0>] (drm_connector_register_all+0x90/0xb8)
> [<c04c87e0>] (drm_connector_register_all) from [<c04cefcc>] (drm_modeset_register_all+0x44/0x6c)
> [<c04cefcc>] (drm_modeset_register_all) from [<c04b4ebc>] (drm_dev_register+0x15c/0x1c0)
> [<c04b4ebc>] (drm_dev_register) from [<c04df2f8>] (pl111_amba_probe+0x2e0/0x4ac)
> [<c04df2f8>] (pl111_amba_probe) from [<c045e8d8>] (amba_probe+0x9c/0x118)

Seeing the same thing on Salvator-XS, due to vga->ddc being -ENODEV.

> # first bad commit: [a4f9087e85de141e4e6d21ac2c583ae096cc9aba] drm/bridge: dumb-vga-dac: Provide ddc symlink in connector sysfs directory

Fix sent
https://lore.kernel.org/lkml/20190813093046.4976-1-geert+renesas@glider.be/

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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