I use Ubuntu 7.04 with 2.6.18.8 , 2.6.20, 2.6.21 kernel vanilla and when I use "make" I get this:

festor@sniper-win :~/rtl-wifi$ make
make -C /lib/modules/2.6.18.8-custom/build M=/home/festor/rtl-wifi modules
make[1]: se ingresa al directorio `/usr/src/linux-2.6.18.8'
  CC [M]  /home/festor/rtl-wifi/ieee80211/ieee80211_softmac.o
  CC [M]  /home/festor/rtl-wifi/ieee80211/ieee80211_rx.o
  CC [M]  /home/festor/rtl-wifi/ieee80211/ieee80211_tx.o
  CC [M]  /home/festor/rtl-wifi/ieee80211/ieee80211_wx.o
  CC [M]  /home/festor/rtl-wifi/ieee80211/ieee80211_module.o
  CC [M]  /home/festor/rtl-wifi/ieee80211/ieee80211_softmac_wx.o
  CC [M]  /home/festor/rtl-wifi/ieee80211/ieee80211_crypt.o
  CC [M]  /home/festor/rtl-wifi/ieee80211/ieee80211_crypt_ccmp.o
  CC [M]  /home/festor/rtl-wifi/ieee80211/ieee80211_crypt_tkip.o
  CC [M]  /home/festor/rtl-wifi/ieee80211/ieee80211_crypt_wep.o
  LD [M]  /home/festor/rtl-wifi/ieee80211/ieee80211- rtl.o
  LD [M]  /home/festor/rtl-wifi/ieee80211/ieee80211_crypt-rtl.o
  LD [M]  /home/festor/rtl-wifi/ieee80211/ieee80211_crypt_wep- rtl.o
  LD [M]  /home/festor/rtl-wifi/ieee80211/ieee80211_crypt_tkip-rtl.o
  LD [M]  /home/festor/rtl-wifi/ieee80211/ieee80211_crypt_ccmp- rtl.o
  CC [M]  /home/festor/rtl-wifi/rtl8187-newstack/r8187_core.o
  CC [M]  /home/festor/rtl-wifi/rtl8187-newstack/r8180_93cx6.o
  CC [M]  /home/festor/rtl-wifi/rtl8187-newstack/r8180_wx.o
  CC [M]  /home/festor/rtl-wifi/rtl8187-newstack/r8180_rtl8225.o
  CC [M]  /home/festor/rtl-wifi/rtl8187-newstack/r8180_rtl8225z2.o
  LD [M]  /home/festor/rtl-wifi/rtl8187-newstack/r8187.o
  CC [M]  /home/festor/rtl-wifi/rtl818x-newstack/r8180_core.o
  CC [M]  /home/festor/rtl-wifi/rtl818x-newstack/r8180_sa2400.o
  CC [M]  /home/festor/rtl-wifi/rtl818x-newstack/r8180_93cx6.o
  CC [M]  /home/festor/rtl-wifi/rtl818x-newstack/r8180_wx.o
/home/festor/rtl-wifi/rtl818x-newstack/r8180_wx.c:469: aviso: se definió 'r8180_wx_set_monitor_type' pero no se usa
  CC [M]  /home/festor/rtl-wifi/rtl818x-newstack/r8180_max2820.o
  CC [M]  /home/festor/rtl-wifi/rtl818x-newstack/r8180_gct.o
  CC [M]  /home/festor/rtl-wifi/rtl818x-newstack/r8180_rtl8225.o
  CC [M]  /home/festor/rtl-wifi/rtl818x-newstack/r8180_rtl8255.o
/home/festor/rtl-wifi/rtl818x-newstack/r8180_rtl8255.c: En la función 'rtl8255_rf_init':
/home/festor/rtl-wifi/rtl818x-newstack/r8180_rtl8255.c:1710: aviso: ISO C90 prohíbe las declaraciones mezcladas y código
  LD [M]  /home/festor/rtl-wifi/rtl818x-newstack/r8180.o
  Building modules, stage 2.
  MODPOST
  CC      /home/festor/rtl-wifi/ieee80211/ieee80211-rtl.mod.o
  LD [M]  /home/festor/rtl-wifi/ieee80211/ieee80211- rtl.ko
  CC      /home/festor/rtl-wifi/ieee80211/ieee80211_crypt-rtl.mod.o
  LD [M]  /home/festor/rtl-wifi/ieee80211/ieee80211_crypt- rtl.ko
  CC      /home/festor/rtl-wifi/ieee80211/ieee80211_crypt_ccmp-rtl.mod.o
  LD [M]  /home/festor/rtl-wifi/ieee80211/ieee80211_crypt_ccmp-rtl.ko
  CC      /home/festor/rtl-wifi/ieee80211/ieee80211_crypt_tkip-rtl.mod.o
  LD [M]  /home/festor/rtl-wifi/ieee80211/ieee80211_crypt_tkip-rtl.ko
  CC      /home/festor/rtl-wifi/ieee80211/ieee80211_crypt_wep- rtl.mod.o
  LD [M]  /home/festor/rtl-wifi/ieee80211/ieee80211_crypt_wep-rtl.ko
  CC      /home/festor/rtl-wifi/rtl8187-newstack/r8187.mod.o
  LD [M]  /home/festor/rtl-wifi/rtl8187-newstack/r8187.ko
  CC      /home/festor/rtl-wifi/rtl818x-newstack/r8180.mod.o
  LD [M]  /home/festor/rtl-wifi/rtl818x-newstack/r8180.ko
make[1]: se sale del directorio `/usr/src/linux-2.6.18.8'

In English:

/home/festor/rtl-wifi/rtl818x-newstack/r8180_wx.c:469: warning: `was defined r8180_wx_set_monitor_type' but it is not used

/home/festor/rtl-wifi/rtl818x-newstack/r8180_rtl8255.c: In the function `rtl8255_rf_init':

/home/festor/rtl-wifi/rtl818x-newstack/r8180_rtl8255.c:1710: warning: ISO C90 prohibits the mixed declarations and code
Building modules, stage 2.
MODPOST

Any ideas?