[Buildroot] libcec needs to be patched to provide a correct libcec.pc

[Buildroot] libcec needs to be patched to provide a correct libcec.pc

[Yann E. MORIN]

Bernd, All,

You previously said (on IRC) that  "libcec needs to be patched in order
to provide a correct libcec.pc"

What I saw is that libcec.pc has:
    Libs: -L${libdir} -lcec

Do you mean it should also have -ludev, like:
    Libs: -L${libdir} -lcec -ludev

The issue I see with adding -ludev is:
  - libcec can not be built static, so it is always built as a .so
  - libcec.so has a DT_NEEDED tag on libudev.so.1
  - normally, the linker will follow the DT_NEEDED flags of .so

So, linking a program against -lcec should be enough (unless that
program itself requires -ludev, but then it should specify it, and
that's unrelated to libcec)

Can you elaborate a bit on why and how we should patch libcec.pc,
please?

Regards,
Yann E. MORIN.

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[Buildroot] libcec needs to be patched to provide a correct libcec.pc

[Bernd Kuhls]

Hi Yann,

"Yann E. MORIN" <yann.morin.1998@free.fr> wrote in 
news:20140613212754.GB16169 at free.fr:

> Can you elaborate a bit on why and how we should patch libcec.pc,
> please?

when libcec finds libudev during configure 
output/staging/usr/lib/pkgconfig/libcec.pc will contain

Requires:  udev

When xbmc configure searches for libcec it finds this requirement and tries 
to find udev.pc, which fails when only libudev is present:

checking for UDEV... yes
configure: == libusb disabled. ==
checking for CEC... no
configure: error: == libcec disabled. CEC adapter support will not be 
available. ==

xbmc/config.log shows:

configure:29084: $PKG_CONFIG --exists --print-errors "libcec >= 2.1.0"
Package udev was not found in the pkg-config search path.
Perhaps you should add the directory containing `udev.pc'
to the PKG_CONFIG_PATH environment variable
No package 'udev' found

So we need to patch libcec/configure.ac in line 237 from 

REQUIRES="$REQUIRES udev"

to

REQUIRES="$REQUIRES libudev"

to make xbmc happy.

Regards, Bernd

[Buildroot] libcec needs to be patched to provide a correct libcec.pc

[Yann E. MORIN]

Bernd, All,

On 2014-06-14 05:52 +0200, Bernd Kuhls spake thusly:
> "Yann E. MORIN" <yann.morin.1998@free.fr> wrote in 
> news:20140613212754.GB16169 at free.fr:
> > Can you elaborate a bit on why and how we should patch libcec.pc,
> > please?
> 
> when libcec finds libudev during configure 
> output/staging/usr/lib/pkgconfig/libcec.pc will contain
> 
> Requires:  udev
> 
> When xbmc configure searches for libcec it finds this requirement and tries 
> to find udev.pc, which fails when only libudev is present:
> 
> checking for UDEV... yes
> configure: == libusb disabled. ==
> checking for CEC... no
> configure: error: == libcec disabled. CEC adapter support will not be 
> available. ==
> 
> xbmc/config.log shows:
> 
> configure:29084: $PKG_CONFIG --exists --print-errors "libcec >= 2.1.0"
> Package udev was not found in the pkg-config search path.
> Perhaps you should add the directory containing `udev.pc'
> to the PKG_CONFIG_PATH environment variable
> No package 'udev' found
> 
> So we need to patch libcec/configure.ac in line 237 from 
> 
> REQUIRES="$REQUIRES udev"
> 
> to
> 
> REQUIRES="$REQUIRES libudev"
> 
> to make xbmc happy.

Ah! OK, I get it now! Thanks for the thorough explanations. :-)

And indeed, my libudev-only small test-case obviously demonstrates the
above:

    $ ls -l staging/usr/lib/pkgconfig/
    total 8
    -rw-r--r-- 1 ymorin ymorin 278 Jun 13 22:58 libcec.pc
->  -rw-r--r-- 1 ymorin ymorin 509 Jun 13 22:49 libudev.pc

    $ cat staging/usr/lib/pkgconfig/libcec.pc
    prefix=/usr
    exec_prefix=/usr
    libdir=${exec_prefix}/lib
    includedir=${prefix}/include

    Name: libcec
    Description: Pulse-Eight CEC adapter library
    URL: http://www.pulse-eight.com/
    Version: 2:1:0
->  Requires:  udev
    Libs: -L${libdir} -lcec
    Cflags: -I${includedir} -I${includedir}/libcec


So, in case we only provide a libudev, can't we just simlink udev.pc to
libudev.pc  (or the other way around) as we won't patch every and all
packages in the wild?

I'll do the symlinking unless there is a good reason not to.

Regards,
Yann E. MORIN.

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
| +33 223 225 172 `------------.-------:  X  AGAINST      |  \e/  There is no  |
| http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
'------------------------------^-------^------------------^--------------------'