Re: Hi, how can I compile udev with cross compilation?

[Paul Bender <pebender@san.rr.com>]

On 2/20/2010 10:20 AM, Dan Nicholson wrote:
> On Sat, Feb 20, 2010 at 8:37 AM, Paul Bender<pebender@san.rr.com>  wrote:
>> On 2/20/2010 1:52 AM, huyle wrote:
>>>
>>> Hi,
>>> I am currently building an linux system for arm board. I am stuck with
>>> udev. So can you help me with some commands to compile udev with cross
>>> compilation?
>>> Thanks for your time
>>
>> I am cross compiling udev, but not for the ARM.
>>
>> The only trouble that I have encountered when cross compiling version 151 is
>> with the configure scripts determination of the pci.ids file location. This
>> is caused by autoconf's AC_CHECK_FILES macro generating an error when cross
>> compiling. However, this can be worked around by setting
>>
>> ac_cv_file__usr_share_pci_ids='no'
>> ac_cv_file__usr_share_hwdata_pci_ids='no'
>> ac_cv_file__usr_share_misc_pci_ids='no'
>>
>> in the build system's environment before running configure and setting the
>> configure script's --with-pci-ids-path argument.
>>
>> I have had this work around for so long that I have not given it much
>> thought. However, it is relatively easy to fix the configure script so that
>> it only attempting to determine the pci.ids file location when
>> --with-pci-ids-path is not set. Therefore, I have created and attached a
>> patch that should do this. Of course, after applying, you would need to
>> rerun autoconf or autoreconf.
>
> I think it would be better to just make the AC_CHECK_FILES conditional
> on cross compiling:
>
> if test $cross_compiling != yes; then
>      AC_CHECK_FILES...pci.ids not found, try --with-pci-ids-path
> else
>      # just assume pciids location
>      pciids=/usr/share/pci.ids
> fi
>
> Otherwise, people cross compiling will bomb unless they pass
> --with-pci-ids-path.

Unless I misunderstand AC_ARG_WITH, its third argument is for what to do 
when the corresponding --with configure argument is not provided, which 
is how it behaves in my build system (with autoconf 2.63). That is why I 
put the AC_CHECK_FILES in the third argument.

I like your patch better than mine as it does not generate the unhelpful 
error message:
"cannot check for file existence when cross compiling".
when the --with-pci-ids-path is not provided.

However, for cross compiling, it might be better to force the user to 
provide --with-pci-ids-path rather than assuming one since an incorrect 
assumed path would not be discovered until on target runtime.

> Likewise, you changed the 'test -n "$pciids"' to
> a 'test -x'. I don't know a lot of people with an executable pci
> database. Attached is a patch to do this.

Doh, that was supposed to be -z. Thanks for the catch.