In Debian(Etch kernel), in directory /slmodem-2.9.11-20080126
the bash command
make KERNEL_DIR=/lib/modules/2.6.18-6-686/build produced warnings and
errors.
Kernel headers, kernel source, and linux-kbuild-2.6.18-6-686 seem to be installed OK.
I used /sbin/lspci' before replacing this modem with a serial controller PCI modem, but scanModem's ModemData.txt lists the Motorola modem as:

"
For candidate card in slot 05:04.0, firmware information and bootup diagnostics
are:
PCI slot PCI ID SubsystemID Name
---------- --------- --------- --------------
05:04.0 1057:3052 1057:3020 Modem: Motorola Unknown device 3052
Modem interrupt assignment and sharing:
--- Bootup diagnostics for card in PCI slot 05:04.0 ----
ACPI: PCI Interrupt 0000:05:04.0[A] -> GSI 16 (level, low) -> IRQ 201
0000:05:04.0: ttyS1 at I/O 0x1008 (irq = 201) is a 16450
0000:05:04.0: ttyS2 at I/O 0x1010 (irq = 201) is a 8250
0000:05:04.0: ttyS3 at I/O 0x1018 (irq = 201) is a 16450
Couldn't register serial port 0000:05:04.0: -28
Predictive diagnostics for card in bus 05:04.0:
Modem chipset detected on
NAME="Modem: Motorola Unknown device 3052 "
CLASS=0703
PCIDEV=1057:3052
SUBSYS=1057:3020
IRQ=201
IDENT=slamr

For candidate modem in: 05:04.0
0703 Modem: Motorola Unknown device 3052
Primary device ID: 1057:3052
Support type needed or chipset: slamr

1057:3052 has a Motorola chipset, poorly supported by Motorola itself
"
Could someone please tell me what else could be needed to install this modem?
Thanks.

...some errors of 'make' command:

modem_main.c:973: error: storage size of 'prm' isn't known
modem_main.c:975: error: L_FUTUREared (first use in this function)
modem_main.c:974: error: L_CURRENTn.c:974: error: ckallwn
modem_main.c:974: warning: implicit declaration of function snm7r: error: L_CURRENTn.c:974: error: ckallwn

apt-get install build-essential
may have helped, or editing the Makefile's first lines to spell out
/lib/modules/2.6.18-6-686/build as the path to the kernel headers may have helped, because make worked, with some warnings, but no errors.
After make install, changing directory into ungrab-winmodem,
modprobe ungrab-winmodem, modprobe slamr, and slmodemd -c USA /dev/slamr0
seemed to create /dev/ttySL0, or at least a symbolic link from /dev/pts/0 to /dev/ttySLO...
but wvdialconf /etc/wvdial.conf can't find a modem, ttySL0 can't be found in /dev, and the file 0 can't be found in /dev/pts