It appears that this dependency is intended for use during src_test(). This dependency is automagic, but only affect test binaries which are not installed. The only case where this is harmful is when cairo.pc is installed but libcairo.so is broken. However, RESTRICT="test" is set. Thus, it would make sense not to build these files unless if the test-phase is enabled. I only tested x11-libs/libdrm-2.4.17. ./configure fragment: `` checking for CAIRO... yes checking for LIBUDEV... yes '' ohnobinki@ohnopublishing ~/liblist-2.1 $ nm /var/tmp/portage/x11-libs/libdrm-2.4.17/work.amd64/libdrm-2.4.17/tests/modetest/modetest.o 0000000000000000 r .LC1 0000000000000000 r .LC3 0000000000000008 r .LC51 0000000000000010 r .LC52 0000000000000018 r .LC54 0000000000000020 r .LC55 0000000000000028 r .LC56 U _IO_getc U __errno_location U __strdup U cairo_arc U cairo_create U cairo_destroy U cairo_fill U cairo_image_surface_create U cairo_image_surface_get_data U cairo_image_surface_get_stride U cairo_line_to U cairo_move_to U cairo_new_sub_path U cairo_set_line_cap U cairo_set_line_width ohnobinki@ohnopublishing ~ $ nm /var/tmp/portage/x11-libs/libdrm-2.4.17/work.amd64/libdrm-2.4.17/tests/.libs/libdrmtest.a |grep udev U udev_device_get_devnode U udev_device_get_parent U udev_device_get_property_value U udev_device_get_subsystem U udev_device_new_from_syspath ... OK, sorry, this is a big bug report about a problem that essentially doesn't exist. Do what you will with it ;-).
Created attachment 214651 [details] /tmp/libdrm-2.4.17-build.log
*** Bug 300213 has been marked as a duplicate of this bug. ***
*** Bug 300646 has been marked as a duplicate of this bug. ***
The attachment for bug 300646 looks promising.
I just ran into this while doing some cross-compiling. It's trivial to fix now, just give --disable-cairo-tests to ./configure.
*** Bug 332271 has been marked as a duplicate of this bug. ***
should be all set now in the tree; thanks for the report! Commit message: Explicitly disable udev/cairo since they are used only by tests http://sources.gentoo.org/x11-libs/libdrm/libdrm-2.4.59-r1.ebuild?rev=1.1