cat /etc/portage/package.mask/x11-drivers
=x11-drivers/xf86-video-nouveau-1.0.2

x11-libs/libdrm:0

  (x11-libs/libdrm-2.4.33::gentoo, installed) pulled in by
    <x11-libs/libdrm-2.4.34 required by (media-libs/mesa-8.0.4-r1::gentoo, installed)

  (x11-libs/libdrm-2.4.39::gentoo, ebuild scheduled for merge) pulled in by
    >=x11-libs/libdrm-2.4.34[video_cards_nouveau] required by (x11-drivers/xf86-video-nouveau-1.0.2::gentoo, ebuild scheduled for merge)

net-misc/curl:0

  (net-misc/curl-7.27.0-r3::gentoo, installed) pulled in by
    (no parents that aren't satisfied by other packages in this slot)

  (net-misc/curl-7.26.0::gentoo, ebuild scheduled for merge) pulled in by
    <net-misc/curl-7.27.0 required by (dev-cpp/libcmis-0.1.0-r1::gentoo, ebuild scheduled for merge)

emerge -pv mesa

These are the packages that would be merged, in order:

Calculating dependencies... done!
[ebuild   R    ] media-libs/mesa-8.0.4-r1  USE="classic egl gallium llvm nptl shared-glapi -bindist -debug -g3dvl -gbm -gles1 -gles2 -openvg -osmesa -pax_kernel -pic (-selinux) -shared-dricore -vdpau (-wayland) -xa -xvmc" VIDEO_CARDS="nouveau -i915 -i965 -intel -r100 -r200 -r300 -r600 -radeon -vmware" 0 kB

Total: 1 package (1 reinstall), Size of downloads: 0 kB

 * IMPORTANT: 7 news items need reading for repository 'gentoo'.
 * Use eselect news to read news items.

emerge --info
Portage 2.3.4-r9 (funtoo/1.0/linux-gnu/arch/x86-64bit, gcc-4.6.2, glibc-2.13-r4, 3.4.4-funtoo-r0a x86_64)
=================================================================
System uname: Linux-3.4.4-funtoo-r0a-x86_64-Intel-R-_Core-TM-2_Quad_CPU_Q6600_@_2.40GHz-with-gentoo-2.2.0
Timestamp of tree: Mon, 08 Oct 2012 05:45:01 +0000
app-shells/bash:          4.2_p24
dev-lang/python:          2.7.3-r1000, 3.2.3-r1000
dev-util/cmake:           2.8.8-r3
sys-apps/baselayout:      2.2.0-r1
sys-apps/openrc:          0.10.2-r2
sys-apps/sandbox:         2.5
sys-devel/autoconf:       2.13, 2.69
sys-devel/automake:       1.11.6
sys-devel/binutils:       2.21.1-r1
sys-devel/gcc:            4.6.2-r1
sys-devel/gcc-config:     1.5
sys-devel/libtool:        2.4.2
sys-devel/make:           3.82-r3
sys-kernel/linux-headers: 2.6.39 (virtual/os-headers)
sys-libs/glibc:           2.13-r4
Repositories: gentoo
ACCEPT_KEYWORDS="amd64 ~amd64"
ACCEPT_LICENSE="* -@EULA"
CBUILD="x86_64-pc-linux-gnu"
CFLAGS="-march=core2 -O2 -pipe"
CHOST="x86_64-pc-linux-gnu"
CONFIG_PROTECT="/etc /usr/share/config /usr/share/gnupg/qualified.txt /var/bind"
CONFIG_PROTECT_MASK="${EPREFIX}/etc/gconf /etc/ca-certificates.conf /etc/env.d /etc/fonts/fonts.conf /etc/gconf /etc/gentoo-release /etc/php/apache2-php5.4/ext-active/ /etc/php/cgi-php5.4/ext-active/ /etc/php/cli-php5.4/ext-active/ /etc/revdep-rebuild /etc/sandbox.d /etc/terminfo /etc/udev/rules.d"
CXXFLAGS="-march=core2 -O2 -pipe"
DISTDIR="/usr/portage/distfiles"
FEATURES="assume-digests binpkg-logs config-protect-if-modified distlocks ebuild-locks fixlafiles news parallel-fetch parse-eapi-ebuild-head preserve-libs protect-owned sandbox sfperms strict unknown-features-warn unmerge-logs unmerge-orphans userfetch"
FFLAGS=""
GENTOO_MIRRORS="http://distfiles.gentoo.org"
LANG="ru_RU.UTF-8"
LC_ALL=""
LDFLAGS="-Wl,-O1 -Wl,--sort-common -Wl,--as-needed"
LINGUAS="ru en"
MAKEOPTS="-j5"
PKGDIR="/usr/portage/packages"
PORTAGE_CONFIGROOT="/"
PORTAGE_TMPDIR="/var/tmp"
PORTDIR="/usr/portage"
PORTDIR_OVERLAY=""
SYNC="git://github.com/funtoo/ports-2012.git"
SYNC_USER="root"
USE="X acl amd64 berkdb bzip2 cracklib crypt cxx dbus djvu ffmpeg flac gdbm iconv ipv6 kde matroska mmx modules mp3 mp4 mpeg mpeg2 mpeg4pt2 mudflap multilib ncurses nls nptl ogg opengl openmp pam pcre png python qt3support qt4 readline sse sse2 ssl tcpd tiff unicode xml zlib" ALSA_CARDS="snd_hda_intel" ALSA_PCM_PLUGINS="adpcm alaw asym copy dmix dshare dsnoop empty extplug file hooks iec958 ioplug ladspa lfloat linear meter mmap_emul mulaw multi null plug rate route share shm softvol" APACHE2_MODULES="actions alias auth_basic authn_alias authn_anon authn_dbm authn_default authn_file authz_dbm authz_default authz_groupfile authz_host authz_owner authz_user autoindex cache cgi cgid dav dav_fs dav_lock deflate dir disk_cache env expires ext_filter file_cache filter headers include info log_config logio mem_cache mime mime_magic negotiation rewrite setenvif speling status unique_id userdir usertrack vhost_alias" CALLIGRA_FEATURES="kexi words flow plan sheets stage tables krita karbon braindump" CAMERAS="ptp2" COLLECTD_PLUGINS="df interface irq load memory rrdtool swap syslog" ELIBC="glibc" GPSD_PROTOCOLS="ashtech aivdm earthmate evermore fv18 garmin garmintxt gpsclock itrax mtk3301 nmea ntrip navcom oceanserver oldstyle oncore rtcm104v2 rtcm104v3 sirf superstar2 timing tsip tripmate tnt ubx" INPUT_DEVICES="evdev synaptics virtualbox" KERNEL="linux" LCD_DEVICES="bayrad cfontz cfontz633 glk hd44780 lb216 lcdm001 mtxorb ncurses text" LIBREOFFICE_EXTENSIONS="presenter-console presenter-minimizer" LINGUAS="ru en" PHP_TARGETS="php5-3" PYTHON_ABIS="2.7 3.2" PYTHON_TARGETS="python2_7" QEMU_SOFTMMU_TARGETS="i386 x86_64" QEMU_USER_TARGETS="i386 x86_64" RUBY_TARGETS="ruby18 ruby19" USERLAND="GNU" VIDEO_CARDS="nouveau" XTABLES_ADDONS="quota2 psd pknock lscan length2 ipv4options ipset ipp2p iface geoip fuzzy condition tee tarpit sysrq steal rawnat logmark ipmark dhcpmac delude chaos account"
Unset:  CPPFLAGS, CTARGET, EMERGE_DEFAULT_OPTS, INSTALL_MASK, PORTAGE_BUNZIP2_COMMAND, PORTAGE_COMPRESS, PORTAGE_COMPRESS_FLAGS, SYNC_UMASK

cat /etc/portage/package.mask/x11-drivers
>=x11-drivers/xf86-video-nouveau-0.0.16_pre20120322

emerge --unmerge x11-libs/libdrm -av
emerge --unmerge media-libs/mesa -av

!!! Multiple package instances within a single package slot have been pulled
!!! into the dependency graph, resulting in a slot conflict:

net-misc/curl:0

  (net-misc/curl-7.27.0-r3::gentoo, installed) pulled in by
    (no parents that aren't satisfied by other packages in this slot)

  (net-misc/curl-7.26.0::gentoo, ebuild scheduled for merge) pulled in by
    <net-misc/curl-7.27.0 required by (dev-cpp/libcmis-0.1.0-r1::gentoo, ebuild scheduled for merge)