linux-stable.git/Documentation, branch v5.4.35 Linux kernel stable tree docs: Fix path to MTD command line partition parser 2020-04-23T08:36:45+00:00 Jonathan Neuschäfer j.neuschaefer@gmx.net 2020-02-18T15:02:19+00:00 7d4adb1d3c69efb1d0d90161cdea75b8dcae80a6 commit fb2511247dc4061fd122d0195838278a4a0b7b59 upstream. cmdlinepart.c has been moved to drivers/mtd/parsers/. Fixes: a3f12a35c91d ("mtd: parsers: Move CMDLINE parser") Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net> Signed-off-by: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit fb2511247dc4061fd122d0195838278a4a0b7b59 upstream.

cmdlinepart.c has been moved to drivers/mtd/parsers/.

Fixes: a3f12a35c91d ("mtd: parsers: Move CMDLINE parser")
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
arm64: tegra: Fix Tegra194 PCIe compatible string 2020-04-23T08:36:30+00:00 Jon Hunter jonathanh@nvidia.com 2020-02-14T13:53:53+00:00 d7b59cd020f73c36b58dd504a302e70fe3e0ec96 [ Upstream commit f9f711efd441ad0d22874be49986d92121862335 ] If the kernel configuration option CONFIG_PCIE_DW_PLAT_HOST is enabled then this can cause the kernel to incorrectly probe the generic designware PCIe platform driver instead of the Tegra194 designware PCIe driver. This causes a boot failure on Tegra194 because the necessary configuration to access the hardware is not performed. The order in which the compatible strings are populated in Device-Tree is not relevant in this case, because the kernel will attempt to probe the device as soon as a driver is loaded and if the generic designware PCIe driver is loaded first, then this driver will be probed first. Therefore, to fix this problem, remove the "snps,dw-pcie" string from the compatible string as we never want this driver to be probe on Tegra194. Fixes: 2602c32f15e7 ("arm64: tegra: Add P2U and PCIe controller nodes to Tegra194 DT") Signed-off-by: Jon Hunter <jonathanh@nvidia.com> Signed-off-by: Thierry Reding <treding@nvidia.com> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit f9f711efd441ad0d22874be49986d92121862335 ]

If the kernel configuration option CONFIG_PCIE_DW_PLAT_HOST is enabled
then this can cause the kernel to incorrectly probe the generic
designware PCIe platform driver instead of the Tegra194 designware PCIe
driver. This causes a boot failure on Tegra194 because the necessary
configuration to access the hardware is not performed.

The order in which the compatible strings are populated in Device-Tree
is not relevant in this case, because the kernel will attempt to probe
the device as soon as a driver is loaded and if the generic designware
PCIe driver is loaded first, then this driver will be probed first.
Therefore, to fix this problem, remove the "snps,dw-pcie" string from
the compatible string as we never want this driver to be probe on
Tegra194.

Fixes: 2602c32f15e7 ("arm64: tegra: Add P2U and PCIe controller nodes to Tegra194 DT")
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
ALSA: hda/realtek - Remove now-unnecessary XPS 13 headphone noise fixups 2020-04-17T08:50:08+00:00 Thomas Hebb tommyhebb@gmail.com 2020-03-30T16:09:39+00:00 f5462668ad944940943ffc628640ca1384cc035e commit f36938aa7440f46a0a365f1cfde5f5985af2bef3 upstream. patch_realtek.c has historically failed to properly configure the PC Beep Hidden Register for the ALC256 codec (among others). Depending on your kernel version, symptoms of this misconfiguration can range from chassis noise, picked up by a poorly-shielded PCBEEP trace, getting amplified and played on your internal speaker and/or headphones to loud feedback, which responds to the "Headphone Mic Boost" ALSA control, getting played through your headphones. For details of the problem, see the patch in this series titled "ALSA: hda/realtek - Set principled PC Beep configuration for ALC256", which fixes the configuration. These symptoms have been most noticed on the Dell XPS 13 9350 and 9360, popular laptops that use the ALC256. As a result, several model-specific fixups have been introduced to try and fix the problem, the most egregious of which locks the "Headphone Mic Boost" control as a hack to minimize noise from a feedback loop that shouldn't have been there in the first place. Now that the underlying issue has been fixed, remove all these fixups. Remaining fixups needed by the XPS 13 are all picked up by existing pin quirks. This change should, for the XPS 13 9350/9360 - Significantly increase volume and audio quality on headphones - Eliminate headphone popping on suspend/resume - Allow "Headphone Mic Boost" to be set again, making the headphone jack fully usable as a microphone jack too. Fixes: 8c69729b4439 ("ALSA: hda - Fix headphone noise after Dell XPS 13 resume back from S3") Fixes: 423cd785619a ("ALSA: hda - Fix headphone noise on Dell XPS 13 9360") Fixes: e4c9fd10eb21 ("ALSA: hda - Apply headphone noise quirk for another Dell XPS 13 variant") Fixes: 1099f48457d0 ("ALSA: hda/realtek: Reduce the Headphone static noise on XPS 9350/9360") Cc: stable@vger.kernel.org Signed-off-by: Thomas Hebb <tommyhebb@gmail.com> Link: https://lore.kernel.org/r/b649a00edfde150cf6eebbb4390e15e0c2deb39a.1585584498.git.tommyhebb@gmail.com Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit f36938aa7440f46a0a365f1cfde5f5985af2bef3 upstream.

patch_realtek.c has historically failed to properly configure the PC
Beep Hidden Register for the ALC256 codec (among others). Depending on
your kernel version, symptoms of this misconfiguration can range from
chassis noise, picked up by a poorly-shielded PCBEEP trace, getting
amplified and played on your internal speaker and/or headphones to loud
feedback, which responds to the "Headphone Mic Boost" ALSA control,
getting played through your headphones. For details of the problem, see
the patch in this series titled "ALSA: hda/realtek - Set principled PC
Beep configuration for ALC256", which fixes the configuration.

These symptoms have been most noticed on the Dell XPS 13 9350 and 9360,
popular laptops that use the ALC256. As a result, several model-specific
fixups have been introduced to try and fix the problem, the most
egregious of which locks the "Headphone Mic Boost" control as a hack to
minimize noise from a feedback loop that shouldn't have been there in
the first place.

Now that the underlying issue has been fixed, remove all these fixups.
Remaining fixups needed by the XPS 13 are all picked up by existing pin
quirks.

This change should, for the XPS 13 9350/9360

 - Significantly increase volume and audio quality on headphones
 - Eliminate headphone popping on suspend/resume
 - Allow "Headphone Mic Boost" to be set again, making the headphone
   jack fully usable as a microphone jack too.

Fixes: 8c69729b4439 ("ALSA: hda - Fix headphone noise after Dell XPS 13 resume back from S3")
Fixes: 423cd785619a ("ALSA: hda - Fix headphone noise on Dell XPS 13 9360")
Fixes: e4c9fd10eb21 ("ALSA: hda - Apply headphone noise quirk for another Dell XPS 13 variant")
Fixes: 1099f48457d0 ("ALSA: hda/realtek: Reduce the Headphone static noise on XPS 9350/9360")
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Hebb <tommyhebb@gmail.com>
Link: https://lore.kernel.org/r/b649a00edfde150cf6eebbb4390e15e0c2deb39a.1585584498.git.tommyhebb@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
ALSA: doc: Document PC Beep Hidden Register on Realtek ALC256 2020-04-17T08:50:07+00:00 Thomas Hebb tommyhebb@gmail.com 2020-03-30T16:09:37+00:00 0f18192b6924bf2a7ed8ffe02568e351c71943e0 commit f128090491c3f5aacef91a863f8c52abf869c436 upstream. This codec (among others) has a hidden set of audio routes, apparently designed to allow PC Beep output without a mixer widget on the output path, which are controlled by an undocumented Realtek vendor register. The default configuration of these routes means that certain inputs aren't accessible, necessitating driver control of the register. However, Realtek has provided no documentation of the register, instead opting to fix issues by providing magic numbers, most of which have been at least somewhat erroneous. These magic numbers then get copied by others into model-specific fixups, leading to a fragmented and buggy set of configurations. To get out of this situation, I've reverse engineered the register by flipping bits and observing how the codec's behavior changes. This commit documents my findings. It does not change any code. Cc: stable@vger.kernel.org Signed-off-by: Thomas Hebb <tommyhebb@gmail.com> Link: https://lore.kernel.org/r/bd69dfdeaf40ff31c4b7b797c829bb320031739c.1585584498.git.tommyhebb@gmail.com Signed-off-by: Takashi Iwai <tiwai@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit f128090491c3f5aacef91a863f8c52abf869c436 upstream.

This codec (among others) has a hidden set of audio routes, apparently
designed to allow PC Beep output without a mixer widget on the output
path, which are controlled by an undocumented Realtek vendor register.
The default configuration of these routes means that certain inputs
aren't accessible, necessitating driver control of the register.
However, Realtek has provided no documentation of the register, instead
opting to fix issues by providing magic numbers, most of which have been
at least somewhat erroneous. These magic numbers then get copied by
others into model-specific fixups, leading to a fragmented and buggy set
of configurations.

To get out of this situation, I've reverse engineered the register by
flipping bits and observing how the codec's behavior changes. This
commit documents my findings. It does not change any code.

Cc: stable@vger.kernel.org
Signed-off-by: Thomas Hebb <tommyhebb@gmail.com>
Link: https://lore.kernel.org/r/bd69dfdeaf40ff31c4b7b797c829bb320031739c.1585584498.git.tommyhebb@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
dt-bindings: net: FMan erratum A050385 2020-04-01T09:01:52+00:00 Madalin Bucur madalin.bucur@nxp.com 2020-03-04T16:04:25+00:00 c211a30c1846cf941c3c1d5589d95b9bc9aa8d73 [ Upstream commit 26d5bb9e4c4b541c475751e015072eb2cbf70d15 ] FMAN DMA read or writes under heavy traffic load may cause FMAN internal resource leak; thus stopping further packet processing. The FMAN internal queue can overflow when FMAN splits single read or write transactions into multiple smaller transactions such that more than 17 AXI transactions are in flight from FMAN to interconnect. When the FMAN internal queue overflows, it can stall further packet processing. The issue can occur with any one of the following three conditions: 1. FMAN AXI transaction crosses 4K address boundary (Errata A010022) 2. FMAN DMA address for an AXI transaction is not 16 byte aligned, i.e. the last 4 bits of an address are non-zero 3. Scatter Gather (SG) frames have more than one SG buffer in the SG list and any one of the buffers, except the last buffer in the SG list has data size that is not a multiple of 16 bytes, i.e., other than 16, 32, 48, 64, etc. With any one of the above three conditions present, there is likelihood of stalled FMAN packet processing, especially under stress with multiple ports injecting line-rate traffic. To avoid situations that stall FMAN packet processing, all of the above three conditions must be avoided; therefore, configure the system with the following rules: 1. Frame buffers must not span a 4KB address boundary, unless the frame start address is 256 byte aligned 2. All FMAN DMA start addresses (for example, BMAN buffer address, FD[address] + FD[offset]) are 16B aligned 3. SG table and buffer addresses are 16B aligned and the size of SG buffers are multiple of 16 bytes, except for the last SG buffer that can be of any size. Additional workaround notes: - Address alignment of 64 bytes is recommended for maximally efficient system bus transactions (although 16 byte alignment is sufficient to avoid the stall condition) - To support frame sizes that are larger than 4K bytes, there are two options: 1. Large single buffer frames that span a 4KB page boundary can be converted into SG frames to avoid transaction splits at the 4KB boundary, 2. Align the large single buffer to 256B address boundaries, ensure that the frame address plus offset is 256B aligned. - If software generated SG frames have buffers that are unaligned and with random non-multiple of 16 byte lengths, before transmitting such frames via FMAN, frames will need to be copied into a new single buffer or multiple buffer SG frame that is compliant with the three rules listed above. Signed-off-by: Madalin Bucur <madalin.bucur@nxp.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 26d5bb9e4c4b541c475751e015072eb2cbf70d15 ]

FMAN DMA read or writes under heavy traffic load may cause FMAN
internal resource leak; thus stopping further packet processing.

The FMAN internal queue can overflow when FMAN splits single
read or write transactions into multiple smaller transactions
such that more than 17 AXI transactions are in flight from FMAN
to interconnect. When the FMAN internal queue overflows, it can
stall further packet processing. The issue can occur with any one
of the following three conditions:

  1. FMAN AXI transaction crosses 4K address boundary (Errata
     A010022)
  2. FMAN DMA address for an AXI transaction is not 16 byte
     aligned, i.e. the last 4 bits of an address are non-zero
  3. Scatter Gather (SG) frames have more than one SG buffer in
     the SG list and any one of the buffers, except the last
     buffer in the SG list has data size that is not a multiple
     of 16 bytes, i.e., other than 16, 32, 48, 64, etc.

With any one of the above three conditions present, there is
likelihood of stalled FMAN packet processing, especially under
stress with multiple ports injecting line-rate traffic.

To avoid situations that stall FMAN packet processing, all of the
above three conditions must be avoided; therefore, configure the
system with the following rules:

  1. Frame buffers must not span a 4KB address boundary, unless
     the frame start address is 256 byte aligned
  2. All FMAN DMA start addresses (for example, BMAN buffer
     address, FD[address] + FD[offset]) are 16B aligned
  3. SG table and buffer addresses are 16B aligned and the size
     of SG buffers are multiple of 16 bytes, except for the last
     SG buffer that can be of any size.

Additional workaround notes:
- Address alignment of 64 bytes is recommended for maximally
efficient system bus transactions (although 16 byte alignment is
sufficient to avoid the stall condition)
- To support frame sizes that are larger than 4K bytes, there are
two options:
  1. Large single buffer frames that span a 4KB page boundary can
     be converted into SG frames to avoid transaction splits at
     the 4KB boundary,
  2. Align the large single buffer to 256B address boundaries,
     ensure that the frame address plus offset is 256B aligned.
- If software generated SG frames have buffers that are unaligned
and with random non-multiple of 16 byte lengths, before
transmitting such frames via FMAN, frames will need to be copied
into a new single buffer or multiple buffer SG frame that is
compliant with the three rules listed above.

Signed-off-by: Madalin Bucur <madalin.bucur@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
modpost: move the namespace field in Module.symvers last 2020-03-25T07:25:55+00:00 Jessica Yu jeyu@kernel.org 2020-03-11T17:01:20+00:00 eba75a365f5549dbb4de9e3dda1aa4d8ca374e5d commit 5190044c2965514a973184ca68ef5fad57a24670 upstream. In order to preserve backwards compatability with kmod tools, we have to move the namespace field in Module.symvers last, as the depmod -e -E option looks at the first three fields in Module.symvers to check symbol versions (and it's expected they stay in the original order of crc, symbol, module). In addition, update an ancient comment above read_dump() in modpost that suggested that the export type field in Module.symvers was optional. I suspect that there were historical reasons behind that comment that are no longer accurate. We have been unconditionally printing the export type since 2.6.18 (commit bd5cbcedf44), which is over a decade ago now. Fix up read_dump() to treat each field as non-optional. I suspect the original read_dump() code treated the export field as optional in order to support pre <= 2.6.18 Module.symvers (which did not have the export type field). Note that although symbol namespaces are optional, the field will not be omitted from Module.symvers if a symbol does not have a namespace. In this case, the field will simply be empty and the next delimiter or end of line will follow. Cc: stable@vger.kernel.org Fixes: cb9b55d21fe0 ("modpost: add support for symbol namespaces") Tested-by: Matthias Maennich <maennich@google.com> Reviewed-by: Matthias Maennich <maennich@google.com> Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com> Signed-off-by: Jessica Yu <jeyu@kernel.org> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 5190044c2965514a973184ca68ef5fad57a24670 upstream.

In order to preserve backwards compatability with kmod tools, we have to
move the namespace field in Module.symvers last, as the depmod -e -E
option looks at the first three fields in Module.symvers to check symbol
versions (and it's expected they stay in the original order of crc,
symbol, module).

In addition, update an ancient comment above read_dump() in modpost that
suggested that the export type field in Module.symvers was optional. I
suspect that there were historical reasons behind that comment that are
no longer accurate. We have been unconditionally printing the export
type since 2.6.18 (commit bd5cbcedf44), which is over a decade ago now.

Fix up read_dump() to treat each field as non-optional. I suspect the
original read_dump() code treated the export field as optional in order
to support pre <= 2.6.18 Module.symvers (which did not have the export
type field). Note that although symbol namespaces are optional, the
field will not be omitted from Module.symvers if a symbol does not have
a namespace. In this case, the field will simply be empty and the next
delimiter or end of line will follow.

Cc: stable@vger.kernel.org
Fixes: cb9b55d21fe0 ("modpost: add support for symbol namespaces")
Tested-by: Matthias Maennich <maennich@google.com>
Reviewed-by: Matthias Maennich <maennich@google.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Jessica Yu <jeyu@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
ACPI: watchdog: Allow disabling WDAT at boot 2020-03-21T07:11:47+00:00 Jean Delvare jdelvare@suse.de 2020-02-06T15:58:45+00:00 20eed76927492b4a2b099e40835e8b9a686f6748 [ Upstream commit 3f9e12e0df012c4a9a7fd7eb0d3ae69b459d6b2c ] In case the WDAT interface is broken, give the user an option to ignore it to let a native driver bind to the watchdog device instead. Signed-off-by: Jean Delvare <jdelvare@suse.de> Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 3f9e12e0df012c4a9a7fd7eb0d3ae69b459d6b2c ]

In case the WDAT interface is broken, give the user an option to
ignore it to let a native driver bind to the watchdog device instead.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
cifs_atomic_open(): fix double-put on late allocation failure 2020-03-18T06:17:51+00:00 Al Viro viro@zeniv.linux.org.uk 2020-03-12T22:25:20+00:00 918ba24a9bbf85cbca33d2f3d5369915d3e7fbd3 commit d9a9f4849fe0c9d560851ab22a85a666cddfdd24 upstream. several iterations of ->atomic_open() calling conventions ago, we used to need fput() if ->atomic_open() failed at some point after successful finish_open(). Now (since 2016) it's not needed - struct file carries enough state to make fput() work regardless of the point in struct file lifecycle and discarding it on failure exits in open() got unified. Unfortunately, I'd missed the fact that we had an instance of ->atomic_open() (cifs one) that used to need that fput(), as well as the stale comment in finish_open() demanding such late failure handling. Trivially fixed... Fixes: fe9ec8291fca "do_last(): take fput() on error after opening to out:" Cc: stable@kernel.org # v4.7+ Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit d9a9f4849fe0c9d560851ab22a85a666cddfdd24 upstream.

several iterations of ->atomic_open() calling conventions ago, we
used to need fput() if ->atomic_open() failed at some point after
successful finish_open().  Now (since 2016) it's not needed -
struct file carries enough state to make fput() work regardless
of the point in struct file lifecycle and discarding it on
failure exits in open() got unified.  Unfortunately, I'd missed
the fact that we had an instance of ->atomic_open() (cifs one)
that used to need that fput(), as well as the stale comment in
finish_open() demanding such late failure handling.  Trivially
fixed...

Fixes: fe9ec8291fca "do_last(): take fput() on error after opening to out:"
Cc: stable@kernel.org # v4.7+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
netfilter: nf_flowtable: fix documentation 2020-03-05T15:43:51+00:00 Matteo Croce mcroce@redhat.com 2020-01-30T19:10:19+00:00 dd3fd6dec30cf7f8657dbc0170e8cc907b4dd1cc commit 78e06cf430934fc3768c342cbebdd1013dcd6fa7 upstream. In the flowtable documentation there is a missing semicolon, the command as is would give this error: nftables.conf:5:27-33: Error: syntax error, unexpected devices, expecting newline or semicolon hook ingress priority 0 devices = { br0, pppoe-data }; ^^^^^^^ nftables.conf:4:12-13: Error: invalid hook (null) flowtable ft { ^^ Fixes: 19b351f16fd9 ("netfilter: add flowtable documentation") Signed-off-by: Matteo Croce <mcroce@redhat.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 78e06cf430934fc3768c342cbebdd1013dcd6fa7 upstream.

In the flowtable documentation there is a missing semicolon, the command
as is would give this error:

    nftables.conf:5:27-33: Error: syntax error, unexpected devices, expecting newline or semicolon
                    hook ingress priority 0 devices = { br0, pppoe-data };
                                            ^^^^^^^
    nftables.conf:4:12-13: Error: invalid hook (null)
            flowtable ft {
                      ^^

Fixes: 19b351f16fd9 ("netfilter: add flowtable documentation")
Signed-off-by: Matteo Croce <mcroce@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
kbuild: remove header compile test 2020-03-05T15:43:47+00:00 Masahiro Yamada yamada.masahiro@socionext.com 2019-11-07T07:14:40+00:00 ef134d8b493c537b81e8cbd56704efff0b402d8a commit fcbb8461fd2376ba3782b5b8bd440c929b8e4980 upstream. There are both positive and negative options about this feature. At first, I thought it was a good idea, but actually Linus stated a negative opinion (https://lkml.org/lkml/2019/9/29/227). I admit it is ugly and annoying. The baseline I'd like to keep is the compile-test of uapi headers. (Otherwise, kernel developers have no way to ensure the correctness of the exported headers.) I will maintain a small build rule in usr/include/Makefile. Remove the other header test functionality. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> [ added to 5.4.y due to start of build warnings from backported patches because of this feature - gregkh] Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit fcbb8461fd2376ba3782b5b8bd440c929b8e4980 upstream.

There are both positive and negative options about this feature.
At first, I thought it was a good idea, but actually Linus stated a
negative opinion (https://lkml.org/lkml/2019/9/29/227). I admit it
is ugly and annoying.

The baseline I'd like to keep is the compile-test of uapi headers.
(Otherwise, kernel developers have no way to ensure the correctness
of the exported headers.)

I will maintain a small build rule in usr/include/Makefile.
Remove the other header test functionality.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
[ added to 5.4.y due to start of build warnings from backported patches
  because of this feature - gregkh]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>