Thread: How to use the pciutils headers and objects?

1. You run the top-level makefile, because the lib makefile says this
> # Expects to be invoked from the top-level Makefile and uses lots of its variables.

You should end up with a library file (.so and/or .a)

You might end up with a separate include directory, containing only those header files which describe the public interface to the library. If not, you need to experiment a little.

Eg

Code:

#include <pci.h>
int main ( ) {
    struct pci_access pci;
    pci_init(&pci);
}

The way you use it would be
gcc -I/path/to/pciutils/include -L/path/to/pciutils/lib prog.c -lpciutils

The red path is the directory where pci.h is included from.
The green path is the directory where the library is located.
The actual library name is libpciutils.so

Does it actually create a .so file?
If so, where is it? (make the -L option point to it).
Also, check it's name is of the form libfoo.so (then pass -lfoo as the option to the compiler).

I have spent about 5 minutes looking at the build files and it looks like the library might be called "libpci".

Tim S.

Thanks for your help guys.
This is going to be long, but please bare with me. This is very important for me, and is actually just a small part of a greater project I have already written (in python).

I don't know how I missed that in the README...

Anyway, this is what I did:

Code:

$ sudo make SHARED=no install-lib
[sudo] password for absurd: 
make -C lib all
make[1]: Entering directory `/home/absurd/Documents/Programming/project/pciutils/lib'
make[1]: Nothing to be done for `all'.
make[1]: Leaving directory `/home/absurd/Documents/Programming/project/pciutils/lib'
install -d -m 755 /usr/local/lib
install -c -m 644 lib/libpci.a /usr/local/lib
install -d -m 755 /usr/local/include/pci /usr/local/lib/pkgconfig
install -c -m 644 lib/config.h lib/header.h lib/pci.h lib/types.h /usr/local/include/pci
install -c -m 644 lib/libpci.pc /usr/local/lib/pkgconfig

And this is how "my_example.c" (slightly changed "example.c") looks like:

Code:

#include <stdio.h>
#include <pci.h>
#include <internal.h>

int main(int argc, char* argv[]) {
    struct pci_access *pacc;
    struct pci_dev *dev;
    u8 cfg_space[4096] = {0};

    pacc = pci_alloc();  /* Get the pci_access structure */

    /* Set all options you want -- here we stick with the defaults */

    pci_init(pacc);     /* Initialize the PCI library */
    pci_scan_bus(pacc); /* We want to get the list of devices */

    for (dev=pacc->devices; dev; dev=dev->next)    { /* Iterate over all devices */

        if (!pci_read_block(dev, 0x0, cfg_space, 2)) {
            // handle error
            return 1;
        }
        printf("vendor id=%x%x\n", cfg_space[0], cfg_space[1]);

    }

    pci_cleanup(pacc);
    return 0;
}

And when I run it with:

Code:

$ gcc my_example.c -Iproject/pciutils/lib/ -lpci

It compiles and run, but:

1. Why do I have to specify -Iproject/pciutils/lib/ ?
   It seems like when I don't specify it, the preprocessor can't find the headers:
   
   
   Code:

   $ gcc my_example.c -lpci
   my_example.c:2:17: fatal error: pci.h: No such file or directory
   #include <pci.h>
            ^
   compilation terminated.

   Now, it is true that I can omit the -Iproject/pciutils/lib/ and do:
   
   Code:

   #include <pci/pci.h>

   but then; a) the pci.h that is used is the one at /usr/include/pci/pci.h which is not the same as the one I just downloaded with the repo (project/pciutils/lib/pci.h), and b) there's no /usr/include/pci/internal.h in /usr/include/pci/, which is used in example.c (and consequently in my_example.c) (CORRECTION: internal.h is not included in example.c, but is required if I want to gain access to some more low-level elements.)
2. The previous item led me to suspect that when I linked the libpci with -lpci I wasn't actually linking the newly installed library, but rather some old one that I already had. so I did an experiment:
   I added printf("flag\n"); in void pci_scan_bus(struct pci_access *a) (you can see that it is invoked in my_example.c):
   
   Code:

   $ git diff
   diff --git a/lib/access.c b/lib/access.c
   index d991129..cc52dd9 100644
   --- a/lib/access.c
   +++ b/lib/access.c
   @@ -16,6 +16,7 @@
    void
    pci_scan_bus(struct pci_access *a)
    {
   +       printf("flag\n");
      a->methods->scan(a);
    }

   recompiled and reinstalled:
   
   Code:

   $ make 
   make -C lib all
   make[1]: Entering directory `/home/absurd/Documents/Programming/project/pciutils/lib'
   gcc -O2 -Wall -W -Wno-parentheses -Wstrict-prototypes -Wmissing-prototypes   -c -o access.o access.c
   rm -f libpci.a
   ar rcs libpci.a init.o access.o generic.o dump.o names.o filter.o names-hash.o names-parse.o names-net.o names-cache.o names-hwdb.o params.o caps.o sysfs.o proc.o i386-ports.o
   ranlib libpci.a
   make[1]: Leaving directory `/home/absurd/Documents/Programming/project/pciutils/lib'
   gcc   lspci.o ls-vpd.o ls-caps.o ls-caps-vendor.o ls-ecaps.o ls-kernel.o ls-tree.o ls-map.o common.o lib/libpci.a  -lz -lresolv -ludev  -o lspci
   gcc   setpci.o common.o lib/libpci.a  -lz -lresolv -ludev -o setpci
   gcc   example.o lib/libpci.a  -lz -lresolv -ludev -o example
   $ sudo make SHARED=no install-lib
   [sudo] password for absurd: 
   make -C lib all
   make[1]: Entering directory `/home/absurd/Documents/Programming/project/pciutils/lib'
   make[1]: Nothing to be done for `all'.
   make[1]: Leaving directory `/home/absurd/Documents/Programming/project/pciutils/lib'
   install -d -m 755 /usr/local/lib
   install -c -m 644 lib/libpci.a /usr/local/lib
   install -d -m 755 /usr/local/include/pci /usr/local/lib/pkgconfig
   install -c -m 644 lib/config.h lib/header.h lib/pci.h lib/types.h /usr/local/include/pci
   install -c -m 644 lib/libpci.pc /usr/local/lib/pkgconfig

   And then when I recompile my_example.c too:
   
   Code:

   gcc my_example.c -Iproject/pciutils/lib/ -lpci

   running ./a.out, I couldn't see the 'flag' printed out.
   So that got me to suspect that I am not linking the correct library...

Any help would be greatly apprecieated.

gcc -M my_example.c -Iproject/pciutils/lib/ -lpci
This will show you which include files get included.

gcc -Wl,-t my_example.c -Iproject/pciutils/lib/ -lpci
This will show you which files/libs are being processed by the linker.

> how can I tell if that's the one that was installed?
Read the log of the install.

install -c -m 644 lib/libpci.a /usr/local/lib

Use the -L option to direct the linker towards a different place (see post #2).

Progressions.

Code:

$ gcc example2.c
example2.c:2:17: fatal error: pci.h: No such file or directory
compilation terminated.

Oh, didn't find where to include pci.h from, so add a -I path.

Code:

$ gcc -I./lib example2.c
/tmp/ccTriEvn.o: In function `main':
example2.c:(.text+0x3f): undefined reference to `pci_alloc'
example2.c:(.text+0x55): undefined reference to `pci_init'
example2.c:(.text+0x64): undefined reference to `pci_scan_bus'
example2.c:(.text+0x98): undefined reference to `pci_read_block'
example2.c:(.text+0xf2): undefined reference to `pci_cleanup'
collect2: error: ld returned 1 exit status

Better, but missing the pci library. So add the -L and -l options.

Code:

$ gcc -I./lib -L./lib example2.c -lpci
./lib/libpci.a(names-parse.o): In function `id_parse_list':
names-parse.c:(.text+0xcc): undefined reference to `gzgets'
names-parse.c:(.text+0x240): undefined reference to `gzeof'
names-parse.c:(.text+0x45f): undefined reference to `gzeof'
./lib/libpci.a(names-parse.o): In function `pci_load_name_list':
names-parse.c:(.text+0x5d5): undefined reference to `gzopen'
names-parse.c:(.text+0x5ff): undefined reference to `gzclose'
names-parse.c:(.text+0x6b3): undefined reference to `gzopen'
names-parse.c:(.text+0x6d9): undefined reference to `gzerror'
names-parse.c:(.text+0x6e9): undefined reference to `gzclose'
names-parse.c:(.text+0x70e): undefined reference to `zError'
names-parse.c:(.text+0x719): undefined reference to `gzclose'
names-parse.c:(.text+0x73a): undefined reference to `gzclose'
./lib/libpci.a(names-hwdb.o): In function `pci_id_hwdb_lookup':
names-hwdb.c:(.text+0xd4): undefined reference to `udev_hwdb_get_properties_list_entry'
names-hwdb.c:(.text+0xe9): undefined reference to `udev_list_entry_get_next'
names-hwdb.c:(.text+0xfd): undefined reference to `udev_list_entry_get_name'
names-hwdb.c:(.text+0x114): undefined reference to `udev_list_entry_get_value'
names-hwdb.c:(.text+0x249): undefined reference to `udev_new'
names-hwdb.c:(.text+0x256): undefined reference to `udev_hwdb_new'
./lib/libpci.a(names-hwdb.o): In function `pci_id_hwdb_free':
names-hwdb.c:(.text+0x27e): undefined reference to `udev_hwdb_unref'
names-hwdb.c:(.text+0x294): undefined reference to `udev_unref'
collect2: error: ld returned 1 exit status

Now we're missing other dependent libraries as well. Find out where they're resolved.
Obviously, 'gz' and 'udev' are common themes, so pick a symbol from each. Where one is, the rest are pretty sure to be found.

Code:

$ find /lib /usr/lib -name "*.a" | xargs nm --print-file-name --extern-only --defined-only 2>/dev/null | grep gzclose
/usr/lib/x86_64-linux-gnu/libz.a:gzclose.o:0000000000000000 T gzclose
/usr/lib/x86_64-linux-gnu/libz.a:gzread.o:0000000000000ea0 T gzclose_r
/usr/lib/x86_64-linux-gnu/libz.a:gzwrite.o:0000000000001170 T gzclose_w
$ find /lib /usr/lib -name "*.a" | xargs nm --print-file-name --extern-only --defined-only 2>/dev/null | grep udev_hwdb_get_properties_list_entry

On my system, libz is installed, but there is nothing for udev. At this point, you hit google to find out the appropriate package name for the missing library.

So anyway, let's try half of it.

Code:

$ gcc -I./lib -L./lib example2.c -lpci -lz
./lib/libpci.a(names-hwdb.o): In function `pci_id_hwdb_lookup':
names-hwdb.c:(.text+0xd4): undefined reference to `udev_hwdb_get_properties_list_entry'
names-hwdb.c:(.text+0xe9): undefined reference to `udev_list_entry_get_next'
names-hwdb.c:(.text+0xfd): undefined reference to `udev_list_entry_get_name'
names-hwdb.c:(.text+0x114): undefined reference to `udev_list_entry_get_value'
names-hwdb.c:(.text+0x249): undefined reference to `udev_new'
names-hwdb.c:(.text+0x256): undefined reference to `udev_hwdb_new'
./lib/libpci.a(names-hwdb.o): In function `pci_id_hwdb_free':
names-hwdb.c:(.text+0x27e): undefined reference to `udev_hwdb_unref'
names-hwdb.c:(.text+0x294): undefined reference to `udev_unref'
collect2: error: ld returned 1 exit status

Good, -lz resolved all the 'z' functions. All that is needed now is to obtain libudev (or whatever it's called).

Yeah, the find command for .so files would be this.

Code:

$ find /lib /usr/lib -name "*.so" | xargs nm --dynamic --print-file-name --extern-only --defined-only 2>/dev/null | grep udev_hwdb_get_properties_list_entry

Glad you're up and running