[Buildroot] [PATCH RFC 0/2] add initial support for libcamera's qcam

[Buildroot] [PATCH RFC 0/2] add initial support for libcamera's qcam

[Quentin Schulz]

This adds initial support for qcam example GUI from libcamera. It is
based on Qt6 and uses openGL.

Sadly, the qt module from meson is currently broken (see first patch in
the series) and requires patching. Upstream isn't really happy with what
I suggested but I haven't understood what they don't like about it so
cannot currently suggest anything better, hence the RFC.

While qcam currently renders the camera liveview, all characters of the
GUI are squares. I have enabled fontconfig and UTF-8 locales but after
building everything (though I dircleaned qt6base once), so not entirely
sure what's missing or if it's PEBKAC, hence the RFC. Though that may be
acceptable? Do not know. Would appreciate pointers on how to debug this
(assumed) font issue.

I'm not planning on actively working on this as the only product we have
that could use this is currently stuck on qt5 so cannot use new qcam and
it would anyway only be for debug firmware releases. See this as a code
dump essentially. If there are hints or limited work required to have
this merged, I'll happily try to find time doing it but feel free to
take over the series or disregard it entirely.

This is based on top of
https://lore.kernel.org/buildroot/20250404-libcamera-0-5-0-v1-0-e2ca9d029aeb@cherry.de/T/#t

Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
---
Quentin Schulz (2):
      package/meson: look for qt6 tools on Buildroot host machine
      package/libcamera: initial support for Qt6 qcam

 package/libcamera/libcamera.mk                     |  5 ++
 ...e-look-for-qt-tools-only-on-build-machine.patch | 56 ++++++++++++++++++++++
 2 files changed, 61 insertions(+)
---
base-commit: 43abcd4c7dd8ad65d2f2012f3d4292362550a3ed
change-id: 20250404-libcamera-qcam-e8269c47e2f9
prerequisite-change-id: 20250404-libcamera-0-5-0-b9ecf899ddb4:v1
prerequisite-patch-id: 854e58d76fc57aa774ca0d315ecae56b67c00c8a
prerequisite-patch-id: 4873ac99203f0d789d64aec048249d9ba6a15a82
prerequisite-patch-id: c4d504c6563a911ba550be263063cfd7bf04bcbe
prerequisite-patch-id: 4a74788db759d3b67650f1456ee4d64f9394f50a
prerequisite-patch-id: 73a4b5a3204b1a901da74a3ffe1672055404dd2f
prerequisite-patch-id: 90b567b9a37abb58747d965ea2e0fef41358844b
prerequisite-patch-id: 946aac34b70f001c24fc6fe86caab759a4591359
prerequisite-patch-id: cee428a4219c83704347f6f194694f21093034da
prerequisite-patch-id: 6bbbdc80dc639a1b2918d79ae101e1030f3312bd

Best regards,
-- 
Quentin Schulz <quentin.schulz@cherry.de>

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[Buildroot] [PATCH RFC 1/2] package/meson: look for qt6 tools on Buildroot host machine

[Quentin Schulz]

From: Quentin Schulz <quentin.schulz@cherry.de>

Qt tools that are looked by the meson qt module are only required as a
build time dependency, to be run on the Buildroot host machine.

Therefore, meson should be looking for them on the host machine and not
on the Buildroot target.

This fixes Buildroot meson not being able to find the qt6 tools whenever
necessary (e.g. for libcamera qcam, whose support is added in a later
commit).

Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
---
 ...e-look-for-qt-tools-only-on-build-machine.patch | 56 ++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/package/meson/0001-qt-module-look-for-qt-tools-only-on-build-machine.patch b/package/meson/0001-qt-module-look-for-qt-tools-only-on-build-machine.patch
new file mode 100644
index 0000000000000000000000000000000000000000..c00ae0dbc3c63296afdc8a3d245091ee8337ddd8
--- /dev/null
+++ b/package/meson/0001-qt-module-look-for-qt-tools-only-on-build-machine.patch
@@ -0,0 +1,56 @@
+From b42daeeb3396df1a02c95d2f583058a74e7854e3 Mon Sep 17 00:00:00 2001
+From: Quentin Schulz <quentin.schulz@cherry.de>
+Date: Tue, 18 Mar 2025 15:07:53 +0100
+Subject: [PATCH] qt module: look for qt tools only on build machine
+
+Qt tools may be needed at build time, let's make their detection based
+on the build machine rather than the host machine as currently done.
+
+This incidentally fixes cross-compilation search for moc, rcc, uic and
+lrelease Qt tools because they are installed in libexec dir and that
+path is somehow not properly looked for otherwise.
+
+Before:
+
+"""
+Detecting Qt6 tools
+Run-time dependency qt6 (modules: Core) found: YES 6.8.1 (pkg-config)
+Program /usr/bin/moc found: NO
+Program /usr/lib/qt6/libexec/moc found: NO
+Program moc6 found: NO
+Program moc-qt6 found: NO
+Program moc found: NO
+"""
+
+After:
+
+"""
+Detecting Qt6 tools
+Found pkg-config: YES (/home/qschulz/work/upstream/buildroot/output/host/bin/pkg-config) 2.3.0
+Build-time dependency qt6 (modules: Core) found: YES 6.8.1 (pkg-config)
+Program /home/qschulz/work/upstream/buildroot/output/host/bin/moc found: NO
+Program /home/qschulz/work/upstream/buildroot/output/host/libexec/moc found: YES 6.8.1 6.8.1 (/home/qschulz/work/upstream/buildroot/output/host/libexec/moc)
+"""
+
+Suggested-by: Ross Burton <ross.burton@arm.com>
+Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
+Upstream: Submitted [https://github.com/mesonbuild/meson/pull/14381]
+Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
+---
+ mesonbuild/modules/_qt.py | 3 +++
+ 1 file changed, 3 insertions(+)
+
+diff --git a/mesonbuild/modules/_qt.py b/mesonbuild/modules/_qt.py
+index 7d52842f9..309068c51 100644
+--- a/mesonbuild/modules/_qt.py
++++ b/mesonbuild/modules/_qt.py
+@@ -270,6 +270,9 @@ class QtBaseModule(ExtensionModule):
+         self._tools_detected = True
+         mlog.log(f'Detecting Qt{self.qt_version} tools')
+         kwargs = {'required': required, 'modules': 'Core', 'method': method}
++        # Tools are for compile-time steps, so force native check for
++        # compatibility with cross-compile scenarios
++        kwargs["native"] = True
+         # Just pick one to make mypy happy
+         qt = T.cast('QtPkgConfigDependency', find_external_dependency(f'qt{self.qt_version}', state.environment, kwargs))
+         if qt.found():

-- 
2.49.0

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[Buildroot] [PATCH RFC 2/2] package/libcamera: initial support for Qt6 qcam

[Quentin Schulz]

From: Quentin Schulz <quentin.schulz@cherry.de>

This enables initial support for Qt6 qcam example application from
libcamera.

fontconfig is recommended otherwise the following messages can be
observed:

"""
QFontDatabase: Cannot find font directory /usr/lib/fonts.
Note that Qt no longer ships fonts. Deploy some (from https://dejavu-fonts.github.io/ for example) or switch to fontconfig.
"""

It seems to depend on UTF-8 as well (via BR2_GENERATE_LOCALE) otherwise
the following messages can be observed:

"""
Detected locale "C" with character encoding "ANSI_X3.4-1968", which is not UTF-8.
Qt depends on a UTF-8 locale, but has failed to switch to one.
If this causes problems, reconfigure your locale. See the locale(1) manual
for more information.
"""

Finally, while qcam starts and renders a liveview, the characters are
still rendered as square characters for now. Not sure what the issue is.

Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
---
 package/libcamera/libcamera.mk | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/package/libcamera/libcamera.mk b/package/libcamera/libcamera.mk
index 6877662bdf02df1c7f8ff37039b3096e96e52481..892f9cf275d9fd117f3a57795220a1673c2455d7 100644
--- a/package/libcamera/libcamera.mk
+++ b/package/libcamera/libcamera.mk
@@ -85,6 +85,11 @@ LIBCAMERA_CONF_OPTS += -Dcam=enabled
 LIBCAMERA_DEPENDENCIES += libevent
 endif
 
+ifeq ($(BR2_PACKAGE_QT6BASE_WIDGETS)$(BR2_PACKAGE_QT6BASE_OPENGL),yy)
+LIBCAMERA_CONF_OPTS += -Dqcam=enabled
+LIBCAMERA_DEPENDENCIES += qt6base
+endif
+
 ifeq ($(BR2_PACKAGE_ELFUTILS),y)
 # Optional dependency on libdw
 LIBCAMERA_DEPENDENCIES += elfutils

-- 
2.49.0

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Re: [Buildroot] [PATCH RFC 0/2] add initial support for libcamera's qcam

[Peter Seiderer via buildroot]

Hello Quentin,

On Tue, 08 Apr 2025 17:16:39 +0200, Quentin Schulz <foss+buildroot@0leil.net> wrote:

> This adds initial support for qcam example GUI from libcamera. It is
> based on Qt6 and uses openGL.
>
> Sadly, the qt module from meson is currently broken (see first patch in
> the series) and requires patching. Upstream isn't really happy with what
> I suggested but I haven't understood what they don't like about it so
> cannot currently suggest anything better, hence the RFC.

The following buildroot patch works for me (for the qcam case):

diff --git a/Makefile b/Makefile
index 5bf5abfe3b..8787a9065f 100644
--- a/Makefile
+++ b/Makefile
@@ -468,7 +468,7 @@ $(STAGING_DIR_SYMLINK): | $(BASE_DIR)
        ln -snf $(STAGING_DIR) $(STAGING_DIR_SYMLINK)

 # Quotes are needed for spaces and all in the original PATH content.
-BR_PATH = "$(HOST_DIR)/bin:$(HOST_DIR)/sbin:$(PATH)"
+BR_PATH = "$(HOST_DIR)/libexec:$(HOST_DIR)/bin:$(HOST_DIR)/sbin:$(PATH)"

 # Location of a file giving a big fat warning that output/target
 # should not be used as the root filesystem.


>
> While qcam currently renders the camera liveview, all characters of the
> GUI are squares. I have enabled fontconfig and UTF-8 locales but after
> building everything (though I dircleaned qt6base once), so not entirely
> sure what's missing or if it's PEBKAC, hence the RFC. Though that may be
> acceptable? Do not know. Would appreciate pointers on how to debug this
> (assumed) font issue.

Font rendering (and video output from a cheap USB cam) seems to work with
the following RPi4 defconfig (and additional 'dtoverlay=vc4-kms-v3d-pi4'):

BR2_arm=y
BR2_cortex_a72=y
BR2_ARM_FPU_NEON_VFPV4=y
BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_6_6=y
BR2_PACKAGE_GLIBC_UTILS=y
BR2_BINUTILS_VERSION_2_44_X=y
BR2_GCC_VERSION_14_X=y
BR2_TOOLCHAIN_BUILDROOT_CXX=y
BR2_PACKAGE_HOST_GDB=y
BR2_GDB_VERSION_16=y
BR2_ENABLE_DEBUG=y
BR2_GLOBAL_PATCH_DIR="board/raspberrypi/patches"
BR2_DOWNLOAD_FORCE_CHECK_HASHES=y
BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_EUDEV=y
BR2_SYSTEM_DHCP="eth0"
BR2_GENERATE_LOCALE="C en_US"
BR2_ROOTFS_POST_BUILD_SCRIPT="board/raspberrypi4/post-build.sh"
BR2_ROOTFS_POST_IMAGE_SCRIPT="board/raspberrypi4/post-image.sh"
BR2_LINUX_KERNEL=y
BR2_LINUX_KERNEL_CUSTOM_TARBALL=y
BR2_LINUX_KERNEL_CUSTOM_TARBALL_LOCATION="$(call github,raspberrypi,linux,576cc10e1ed50a9eacffc7a05c796051d7343ea4)/linux-576cc10e1ed50a9eacffc7a05c796051d7343ea4.tar.gz"
BR2_LINUX_KERNEL_DEFCONFIG="bcm2711"
BR2_LINUX_KERNEL_DTS_SUPPORT=y
BR2_LINUX_KERNEL_INTREE_DTS_NAME="broadcom/bcm2711-rpi-4-b broadcom/bcm2711-rpi-400 broadcom/bcm2711-rpi-cm4 broadcom/bcm2711-rpi-cm4s"
BR2_LINUX_KERNEL_NEEDS_HOST_OPENSSL=y
BR2_PACKAGE_BUSYBOX_SHOW_OTHERS=y
BR2_PACKAGE_XZ=y
BR2_PACKAGE_STRACE=y
BR2_PACKAGE_DEJAVU=y
BR2_PACKAGE_MESA3D=y
BR2_PACKAGE_MESA3D_GALLIUM_DRIVER_V3D=y
BR2_PACKAGE_MESA3D_OPENGL_ES=y
BR2_PACKAGE_QT6=y
BR2_PACKAGE_QT6BASE_GUI=y
BR2_PACKAGE_QT6BASE_EGLFS=y
BR2_PACKAGE_QT6BASE_DEFAULT_QPA="eglfs"
BR2_PACKAGE_QT6BASE_FONTCONFIG=y
BR2_PACKAGE_QT6BASE_HARFBUZZ=y
BR2_PACKAGE_QT6BASE_GIF=y
BR2_PACKAGE_QT6BASE_JPEG=y
BR2_PACKAGE_QT6BASE_PNG=y
BR2_PACKAGE_QT6BASE_WIDGETS=y
BR2_PACKAGE_QT6BASE_NETWORK=y
BR2_PACKAGE_RPI_FIRMWARE=y
BR2_PACKAGE_RPI_FIRMWARE_VARIANT_PI4=y
BR2_PACKAGE_RPI_FIRMWARE_CONFIG_FILE="board/raspberrypi4/config_4.txt"
BR2_PACKAGE_LIBEXIF=y
BR2_PACKAGE_TIFF=y
BR2_PACKAGE_LIBV4L=y
BR2_PACKAGE_LIBV4L_UTILS=y
BR2_PACKAGE_LIBXKBCOMMON=y
BR2_PACKAGE_LIBCAMERA=y
BR2_PACKAGE_OPENSSH=y
BR2_PACKAGE_BASH=y
BR2_PACKAGE_SUDO=y
BR2_PACKAGE_KMOD_TOOLS=y
BR2_TARGET_ROOTFS_EXT2=y
BR2_TARGET_ROOTFS_EXT2_4=y
BR2_TARGET_ROOTFS_EXT2_SIZE="256M"
# BR2_TARGET_ROOTFS_TAR is not set
BR2_PACKAGE_HOST_DOSFSTOOLS=y
BR2_PACKAGE_HOST_GENIMAGE=y
BR2_PACKAGE_HOST_KMOD_XZ=y
BR2_PACKAGE_HOST_MTOOLS=y

The UTF-8 locale warning vanishes if I start qcam with

	$ LANG=C.UTF-8 qcam

or

	$ LANG=en_US.UTF-8 qcam

Regards,
Peter

>
> I'm not planning on actively working on this as the only product we have
> that could use this is currently stuck on qt5 so cannot use new qcam and
> it would anyway only be for debug firmware releases. See this as a code
> dump essentially. If there are hints or limited work required to have
> this merged, I'll happily try to find time doing it but feel free to
> take over the series or disregard it entirely.
>
> This is based on top of
> https://lore.kernel.org/buildroot/20250404-libcamera-0-5-0-v1-0-e2ca9d029aeb@cherry.de/T/#t
>
> Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
> ---
> Quentin Schulz (2):
>       package/meson: look for qt6 tools on Buildroot host machine
>       package/libcamera: initial support for Qt6 qcam
>
>  package/libcamera/libcamera.mk                     |  5 ++
>  ...e-look-for-qt-tools-only-on-build-machine.patch | 56 ++++++++++++++++++++++
>  2 files changed, 61 insertions(+)
> ---
> base-commit: 43abcd4c7dd8ad65d2f2012f3d4292362550a3ed
> change-id: 20250404-libcamera-qcam-e8269c47e2f9
> prerequisite-change-id: 20250404-libcamera-0-5-0-b9ecf899ddb4:v1
> prerequisite-patch-id: 854e58d76fc57aa774ca0d315ecae56b67c00c8a
> prerequisite-patch-id: 4873ac99203f0d789d64aec048249d9ba6a15a82
> prerequisite-patch-id: c4d504c6563a911ba550be263063cfd7bf04bcbe
> prerequisite-patch-id: 4a74788db759d3b67650f1456ee4d64f9394f50a
> prerequisite-patch-id: 73a4b5a3204b1a901da74a3ffe1672055404dd2f
> prerequisite-patch-id: 90b567b9a37abb58747d965ea2e0fef41358844b
> prerequisite-patch-id: 946aac34b70f001c24fc6fe86caab759a4591359
> prerequisite-patch-id: cee428a4219c83704347f6f194694f21093034da
> prerequisite-patch-id: 6bbbdc80dc639a1b2918d79ae101e1030f3312bd
>
> Best regards,

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Re: [Buildroot] [PATCH RFC 0/2] add initial support for libcamera's qcam

[Quentin Schulz via buildroot]

Hi Peter,

On 4/10/25 3:54 PM, Peter Seiderer wrote:
> Hello Quentin,
> 
> On Tue, 08 Apr 2025 17:16:39 +0200, Quentin Schulz <foss+buildroot@0leil.net> wrote:
> 
>> This adds initial support for qcam example GUI from libcamera. It is
>> based on Qt6 and uses openGL.
>>
>> Sadly, the qt module from meson is currently broken (see first patch in
>> the series) and requires patching. Upstream isn't really happy with what
>> I suggested but I haven't understood what they don't like about it so
>> cannot currently suggest anything better, hence the RFC.
> 
> The following buildroot patch works for me (for the qcam case):
> 
> diff --git a/Makefile b/Makefile
> index 5bf5abfe3b..8787a9065f 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -468,7 +468,7 @@ $(STAGING_DIR_SYMLINK): | $(BASE_DIR)
>          ln -snf $(STAGING_DIR) $(STAGING_DIR_SYMLINK)
> 
>   # Quotes are needed for spaces and all in the original PATH content.
> -BR_PATH = "$(HOST_DIR)/bin:$(HOST_DIR)/sbin:$(PATH)"
> +BR_PATH = "$(HOST_DIR)/libexec:$(HOST_DIR)/bin:$(HOST_DIR)/sbin:$(PATH)"
> 
>   # Location of a file giving a big fat warning that output/target
>   # should not be used as the root filesystem.
> 

OK so this "works".

The issue is that meson still believes it's looking for a runtime 
dependency (though it finds the binaries and runs them on Buildroot host 
machine).

I guess this is possibly more acceptable for Buildroot (and in any case 
not exclusive with the meson patch) as /libexec stores binaries that 
could be executed? Though [1] says "internal binaries that are not 
intended to be executed directly by users or shell scripts".

[1] https://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch04s07.html

> 
>>
>> While qcam currently renders the camera liveview, all characters of the
>> GUI are squares. I have enabled fontconfig and UTF-8 locales but after
>> building everything (though I dircleaned qt6base once), so not entirely
>> sure what's missing or if it's PEBKAC, hence the RFC. Though that may be
>> acceptable? Do not know. Would appreciate pointers on how to debug this
>> (assumed) font issue.
> 
> Font rendering (and video output from a cheap USB cam) seems to work with
> the following RPi4 defconfig (and additional 'dtoverlay=vc4-kms-v3d-pi4'):
> 
> BR2_arm=y
> BR2_cortex_a72=y
> BR2_ARM_FPU_NEON_VFPV4=y
> BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_6_6=y
> BR2_PACKAGE_GLIBC_UTILS=y
> BR2_BINUTILS_VERSION_2_44_X=y
> BR2_GCC_VERSION_14_X=y
> BR2_TOOLCHAIN_BUILDROOT_CXX=y
> BR2_PACKAGE_HOST_GDB=y
> BR2_GDB_VERSION_16=y
> BR2_ENABLE_DEBUG=y
> BR2_GLOBAL_PATCH_DIR="board/raspberrypi/patches"
> BR2_DOWNLOAD_FORCE_CHECK_HASHES=y
> BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_EUDEV=y
> BR2_SYSTEM_DHCP="eth0"
> BR2_GENERATE_LOCALE="C en_US"
> BR2_ROOTFS_POST_BUILD_SCRIPT="board/raspberrypi4/post-build.sh"
> BR2_ROOTFS_POST_IMAGE_SCRIPT="board/raspberrypi4/post-image.sh"
> BR2_LINUX_KERNEL=y
> BR2_LINUX_KERNEL_CUSTOM_TARBALL=y
> BR2_LINUX_KERNEL_CUSTOM_TARBALL_LOCATION="$(call github,raspberrypi,linux,576cc10e1ed50a9eacffc7a05c796051d7343ea4)/linux-576cc10e1ed50a9eacffc7a05c796051d7343ea4.tar.gz"
> BR2_LINUX_KERNEL_DEFCONFIG="bcm2711"
> BR2_LINUX_KERNEL_DTS_SUPPORT=y
> BR2_LINUX_KERNEL_INTREE_DTS_NAME="broadcom/bcm2711-rpi-4-b broadcom/bcm2711-rpi-400 broadcom/bcm2711-rpi-cm4 broadcom/bcm2711-rpi-cm4s"
> BR2_LINUX_KERNEL_NEEDS_HOST_OPENSSL=y
> BR2_PACKAGE_BUSYBOX_SHOW_OTHERS=y
> BR2_PACKAGE_XZ=y
> BR2_PACKAGE_STRACE=y
> BR2_PACKAGE_DEJAVU=y
> BR2_PACKAGE_MESA3D=y
> BR2_PACKAGE_MESA3D_GALLIUM_DRIVER_V3D=y
> BR2_PACKAGE_MESA3D_OPENGL_ES=y
> BR2_PACKAGE_QT6=y
> BR2_PACKAGE_QT6BASE_GUI=y
> BR2_PACKAGE_QT6BASE_EGLFS=y
> BR2_PACKAGE_QT6BASE_DEFAULT_QPA="eglfs"
> BR2_PACKAGE_QT6BASE_FONTCONFIG=y
> BR2_PACKAGE_QT6BASE_HARFBUZZ=y
> BR2_PACKAGE_QT6BASE_GIF=y
> BR2_PACKAGE_QT6BASE_JPEG=y
> BR2_PACKAGE_QT6BASE_PNG=y
> BR2_PACKAGE_QT6BASE_WIDGETS=y
> BR2_PACKAGE_QT6BASE_NETWORK=y
> BR2_PACKAGE_RPI_FIRMWARE=y
> BR2_PACKAGE_RPI_FIRMWARE_VARIANT_PI4=y
> BR2_PACKAGE_RPI_FIRMWARE_CONFIG_FILE="board/raspberrypi4/config_4.txt"
> BR2_PACKAGE_LIBEXIF=y
> BR2_PACKAGE_TIFF=y
> BR2_PACKAGE_LIBV4L=y
> BR2_PACKAGE_LIBV4L_UTILS=y
> BR2_PACKAGE_LIBXKBCOMMON=y
> BR2_PACKAGE_LIBCAMERA=y
> BR2_PACKAGE_OPENSSH=y
> BR2_PACKAGE_BASH=y
> BR2_PACKAGE_SUDO=y
> BR2_PACKAGE_KMOD_TOOLS=y
> BR2_TARGET_ROOTFS_EXT2=y
> BR2_TARGET_ROOTFS_EXT2_4=y
> BR2_TARGET_ROOTFS_EXT2_SIZE="256M"
> # BR2_TARGET_ROOTFS_TAR is not set
> BR2_PACKAGE_HOST_DOSFSTOOLS=y
> BR2_PACKAGE_HOST_GENIMAGE=y
> BR2_PACKAGE_HOST_KMOD_XZ=y
> BR2_PACKAGE_HOST_MTOOLS=y
> 
> The UTF-8 locale warning vanishes if I start qcam with
> 
> 	$ LANG=C.UTF-8 qcam
> 
> or
> 
> 	$ LANG=en_US.UTF-8 qcam
> 

Removed all the BSP parts and could generate a rootfs for my PX30 
Ringneck that displayed everything...

Looking into which exact package/symbol is actually required to make 
this work so I can add it as a dependency. Or... is that expected from 
the user to figure out what exactly is needed and compile the app with 
broken font-rendering (though working camera preview)?

Thanks for the hints,
Quentin
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Re: [Buildroot] [PATCH RFC 1/2] package/meson: look for qt6 tools on Buildroot host machine

[Arnout Vandecappelle via buildroot]

On 08/04/2025 17:16, Quentin Schulz wrote:
> From: Quentin Schulz <quentin.schulz@cherry.de>
> 
> Qt tools that are looked by the meson qt module are only required as a
> build time dependency, to be run on the Buildroot host machine.
> 
> Therefore, meson should be looking for them on the host machine and not
> on the Buildroot target.
> 
> This fixes Buildroot meson not being able to find the qt6 tools whenever
> necessary (e.g. for libcamera qcam, whose support is added in a later
> commit).

  As mentioned in the other thread, we should take the upstream fixes instead.

  Regards,
  Arnout

> 
> Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
> ---
>   ...e-look-for-qt-tools-only-on-build-machine.patch | 56 ++++++++++++++++++++++
>   1 file changed, 56 insertions(+)
> 
> diff --git a/package/meson/0001-qt-module-look-for-qt-tools-only-on-build-machine.patch b/package/meson/0001-qt-module-look-for-qt-tools-only-on-build-machine.patch
> new file mode 100644
> index 0000000000000000000000000000000000000000..c00ae0dbc3c63296afdc8a3d245091ee8337ddd8
> --- /dev/null
> +++ b/package/meson/0001-qt-module-look-for-qt-tools-only-on-build-machine.patch
> @@ -0,0 +1,56 @@
> +From b42daeeb3396df1a02c95d2f583058a74e7854e3 Mon Sep 17 00:00:00 2001
> +From: Quentin Schulz <quentin.schulz@cherry.de>
> +Date: Tue, 18 Mar 2025 15:07:53 +0100
> +Subject: [PATCH] qt module: look for qt tools only on build machine
> +
> +Qt tools may be needed at build time, let's make their detection based
> +on the build machine rather than the host machine as currently done.
> +
> +This incidentally fixes cross-compilation search for moc, rcc, uic and
> +lrelease Qt tools because they are installed in libexec dir and that
> +path is somehow not properly looked for otherwise.
> +
> +Before:
> +
> +"""
> +Detecting Qt6 tools
> +Run-time dependency qt6 (modules: Core) found: YES 6.8.1 (pkg-config)
> +Program /usr/bin/moc found: NO
> +Program /usr/lib/qt6/libexec/moc found: NO
> +Program moc6 found: NO
> +Program moc-qt6 found: NO
> +Program moc found: NO
> +"""
> +
> +After:
> +
> +"""
> +Detecting Qt6 tools
> +Found pkg-config: YES (/home/qschulz/work/upstream/buildroot/output/host/bin/pkg-config) 2.3.0
> +Build-time dependency qt6 (modules: Core) found: YES 6.8.1 (pkg-config)
> +Program /home/qschulz/work/upstream/buildroot/output/host/bin/moc found: NO
> +Program /home/qschulz/work/upstream/buildroot/output/host/libexec/moc found: YES 6.8.1 6.8.1 (/home/qschulz/work/upstream/buildroot/output/host/libexec/moc)
> +"""
> +
> +Suggested-by: Ross Burton <ross.burton@arm.com>
> +Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
> +Upstream: Submitted [https://github.com/mesonbuild/meson/pull/14381]
> +Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
> +---
> + mesonbuild/modules/_qt.py | 3 +++
> + 1 file changed, 3 insertions(+)
> +
> +diff --git a/mesonbuild/modules/_qt.py b/mesonbuild/modules/_qt.py
> +index 7d52842f9..309068c51 100644
> +--- a/mesonbuild/modules/_qt.py
> ++++ b/mesonbuild/modules/_qt.py
> +@@ -270,6 +270,9 @@ class QtBaseModule(ExtensionModule):
> +         self._tools_detected = True
> +         mlog.log(f'Detecting Qt{self.qt_version} tools')
> +         kwargs = {'required': required, 'modules': 'Core', 'method': method}
> ++        # Tools are for compile-time steps, so force native check for
> ++        # compatibility with cross-compile scenarios
> ++        kwargs["native"] = True
> +         # Just pick one to make mypy happy
> +         qt = T.cast('QtPkgConfigDependency', find_external_dependency(f'qt{self.qt_version}', state.environment, kwargs))
> +         if qt.found():
> 

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