[Buildroot] [PATCH v2] eudev: generate hwdb.bin at system startup

[Matthew Weber]

Carlos,

On Tue, Oct 16, 2018 at 6:50 AM Carlos Santos <casantos at datacom.com.br> wrote:
>
> From: Carlos Santos <casantos at datacom.ind.br>
>
> Programs that use libudev (e.g. lsusb, from usbutils) need the hwdb.bin
> file to work properly.

Sounds like a great runtime test?  I had wondered other then testing
that the .bin generates, what's the example with those tools to show
the bin is working?

>
> If BR2_PACKAGE_EUDEV_ENABLE_HWDB is selected then the eudev installation
> populates /etc/udev/hwdb.d/ but does not genarete /etc/udev/hwdb.bin. It
> must be created running "udevadm hwdb --update" on the target device but
> this does not work with a read-only /etc, so we need these changes:
>
> - Add the BR2_PACKAGE_EUDEV_HWDB_BIN_PATH config, allowing the user to
>   set the location of hwdb.bin.
> - Patch the configuration script, allowing to set the hwdb.bin path by
>   means of an environment variable (udevhwdbbinpath).
> - Pass the value set in BR2_PACKAGE_EUDEV_HWDB_BIN_PATH to the configure
>   script by means of the udevhwdbbinpath variable.
> - Make the S10udev init script run "udevadm hwdb --update" to recreate
>   hwdb.bin or print an error message if the operation fails (e.g. no
>   write permission on the filesystem).
>
> Signed-off-by: Carlos Santos <casantos at datacom.ind.br>
> Tested-by: Matt Weber <matthew.weber at rockwellcollins.com>
> ---
> Changes v1->v2
> - Incorporate fixes and improvements provided by Matt Weber
>
> Note: there was a discussion via email and on IRC, with suggetsions to
> prebuild hwdb.bin at build time and to add a /etc/defaults/udev cfg file
> instead patching S10udev (like in the recent S01logging suggested
> updates). I like both suggestions but I'd prefer to implement them in
> subsequent patches rather, since they woud require additional changes
> (e.g. adding eudev as a host tool).

Guessing the use of SED setting that value maybe a sticking point
where there would be a push to use the default cfg approach.  Wouldn't
need to be an offline build in this patchset.

> ---
>  package/eudev/Config.in |  9 +++++++++
>  package/eudev/S10udev   |  8 +++++++-
>  package/eudev/eudev.mk  | 13 ++++++++++++-
>  3 files changed, 28 insertions(+), 2 deletions(-)
>
> diff --git a/package/eudev/Config.in b/package/eudev/Config.in
> index 2220265a55..a589a14af3 100644
> --- a/package/eudev/Config.in
> +++ b/package/eudev/Config.in
> @@ -32,6 +32,15 @@ config BR2_PACKAGE_EUDEV_ENABLE_HWDB
>         help
>           Enables hardware database installation to /etc/udev/hwdb.d
>
> +config BR2_PACKAGE_EUDEV_HWDB_BIN_PATH

I believe the dependency needs reflected here on
BR2_PACKAGE_EUDEV_ENABLE_HWDB?  Wouldn't that be the case?

> +       string "hwdb.bin path"
> +       default "/etc/udev/hwdb.bin"
> +       help
> +         Location of the hwdb.bin file, which is re-generated at system
> +         startup. The default is /etc/udev/hwdb.bin but you may want to
> +         move it elsewhere (e.g. /var/run/udev/hwdb.bin) if /etc is in
> +         a read-only filesystem.
> +
>  endif
>
>  comment "eudev needs eudev /dev management"
> diff --git a/package/eudev/S10udev b/package/eudev/S10udev
> index 4e799d6507..08aca82dd9 100755
> --- a/package/eudev/S10udev
> +++ b/package/eudev/S10udev
> @@ -21,14 +21,20 @@ UDEV_CONFIG=/etc/udev/udev.conf
>  test -r $UDEV_CONFIG || exit 6
>  . $UDEV_CONFIG
>
> +UDEV_HWDB_BIN=%%UDEV_HWDB_BIN%%
> +
>  case "$1" in
>      start)
>          printf "Populating %s using udev: " "${udev_root:-/dev}"
>          [ -e /proc/sys/kernel/hotplug ] && printf '\000\000\000\000' > /proc/sys/kernel/hotplug
>          /sbin/udevd -d || { echo "FAIL"; exit 1; }
> +        echo "done"
>          udevadm trigger --type=subsystems --action=add
>          udevadm trigger --type=devices --action=add
> -        udevadm settle --timeout=30 || echo "udevadm settle failed"
> +        udevadm settle --timeout=30 || { echo "udevadm settle failed" && exit 1; }
> +        echo "done"
> +        printf "Compiling hardware database information $UDEV_HWDB_BIN: "
> +        udevadm hwdb --update || { echo "FAIL" && exit 1; }
>          echo "done"
>          ;;
>      stop)
> diff --git a/package/eudev/eudev.mk b/package/eudev/eudev.mk
> index 11dc93762b..0a9c9d5a67 100644
> --- a/package/eudev/eudev.mk
> +++ b/package/eudev/eudev.mk
> @@ -44,8 +44,19 @@ else
>  EUDEV_CONF_OPTS += --disable-selinux
>  endif
>
> +define EUDEV_POST_PATCH
> +       $(SED) 's,$${udevconfdir}/hwdb.bin,$${udevhwdbbinpath:-$${udevconfdir}/hwdb.bin},' \
> +               $(@D)/configure
> +endef
> +EUDEV_POST_PATCH_HOOKS += EUDEV_POST_PATCH
> +
> +EUDEV_CONF_ENV += udevhwdbbinpath=$(BR2_PACKAGE_EUDEV_HWDB_BIN_PATH)
> +
>  define EUDEV_INSTALL_INIT_SYSV
> -       $(INSTALL) -D -m 0755 package/eudev/S10udev $(TARGET_DIR)/etc/init.d/S10udev
> +       $(INSTALL) -D -m 0755 package/eudev/S10udev \
> +               $(TARGET_DIR)/etc/init.d/S10udev
> +       $(SED) 's,%%UDEV_HWDB_BIN%%,$(BR2_PACKAGE_EUDEV_HWDB_BIN_PATH),' \
> +               $(TARGET_DIR)/etc/init.d/S10udev
>  endef
>
>  # Required by default rules for input devices
> --
> 2.14.4
>


-- 
Matthew L Weber / Pr Software Engineer
Airborne Information Systems / RC Linux Secure Platforms
MS 131-100, C Ave NE, Cedar Rapids, IA, 52498, USA
www.rockwellcollins.com

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