Question

I’m currently trying to compile a Linux USB UART driver, which is provided here:
http://www.exar.com/connectivity/uart-and-bridging-solutions/usb-uarts/xr21v1410

The driver consists of 2 header files and one large C file. These are the contents of the Makefile:

obj-m := vizzini.o

KERNELDIR ?= /lib/modules/$(shell uname -r)/build
PWD       := $(shell pwd)

EXTRA_CFLAGS    := -DDEBUG=0

all:
    $(MAKE) -C $(KERNELDIR) M=$(PWD)

modules_install:
    $(MAKE) -C $(KERNELDIR) M=$(PWD) modules_install

clean:
    rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions vtty

This is the error the compiler is throwing when I run make:

[sj755@localhost xr21v141x-lnx-2.6.35-pak]$ make
make -C /lib/modules/3.4.9-2.fc16.x86_64/build M=/home/sj755/Downloads/xr21v141x-lnx-2.6.35-pak
make[1]: Entering directory `/usr/src/kernels/3.4.9-2.fc16.x86_64'
  LD      /home/sj755/Downloads/xr21v141x-lnx-2.6.35-pak/built-in.o
  CC [M]  /home/sj755/Downloads/xr21v141x-lnx-2.6.35-pak/vizzini.o
/home/sj755/Downloads/xr21v141x-lnx-2.6.35-pak/vizzini.c:1643:9: warning: initialization from incompatible pointer type [enabled by default]
/home/sj755/Downloads/xr21v141x-lnx-2.6.35-pak/vizzini.c:1643:9: warning: (near initialization for ‘vizzini_device.ioctl’) [enabled by default]
/home/sj755/Downloads/xr21v141x-lnx-2.6.35-pak/vizzini.c:1646:9: warning: initialization from incompatible pointer type [enabled by default]
/home/sj755/Downloads/xr21v141x-lnx-2.6.35-pak/vizzini.c:1646:9: warning: (near initialization for ‘vizzini_device.tiocmget’) [enabled by default]
/home/sj755/Downloads/xr21v141x-lnx-2.6.35-pak/vizzini.c:1647:9: warning: initialization from incompatible pointer type [enabled by default]
/home/sj755/Downloads/xr21v141x-lnx-2.6.35-pak/vizzini.c:1647:9: warning: (near initialization for ‘vizzini_device.tiocmset’) [enabled by default]
/home/sj755/Downloads/xr21v141x-lnx-2.6.35-pak/vizzini.c: In function ‘vizzini_init’:
/home/sj755/Downloads/xr21v141x-lnx-2.6.35-pak/vizzini.c:1663:9: error: implicit declaration of function ‘usb_serial_register’ [-Werror=implicit-function-declaration]
/home/sj755/Downloads/xr21v141x-lnx-2.6.35-pak/vizzini.c:1677:9: error: implicit declaration of function ‘usb_serial_deregister’ [-Werror=implicit-function-declaration]
/home/sj755/Downloads/xr21v141x-lnx-2.6.35-pak/vizzini.c: In function ‘__check_debug’:
/home/sj755/Downloads/xr21v141x-lnx-2.6.35-pak/vizzini.c:1698:83: warning: return from incompatible pointer type [enabled by default]
cc1: some warnings being treated as errors
make[2]: *** [/home/sj755/Downloads/xr21v141x-lnx-2.6.35-pak/vizzini.o] Error 1
make[1]: *** [_module_/home/sj755/Downloads/xr21v141x-lnx-2.6.35-pak] Error 2
make[1]: Leaving directory `/usr/src/kernels/3.4.9-2.fc16.x86_64'
make: *** [all] Error 2

These are the headers included in the main c source file:

#include <linux/kernel.h>
#include <linux/jiffies.h>
#include <linux/errno.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/module.h>
#include <linux/usb.h>
#include <linux/usb/serial.h>
#include <linux/serial.h>
#include <linux/slab.h>
#include <asm/unaligned.h>
#include <asm/uaccess.h>

#include <linux/usb/cdc.h>
#ifndef CDC_DATA_INTERFACE_TYPE
#define CDC_DATA_INTERFACE_TYPE 0x0a
#endif
#ifndef USB_RT_ACM
#define USB_RT_ACM      (USB_TYPE_CLASS | USB_RECIP_INTERFACE)
#define ACM_CTRL_DTR            0x01
#define ACM_CTRL_RTS            0x02
#define ACM_CTRL_DCD            0x01
#define ACM_CTRL_DSR            0x02
#define ACM_CTRL_BRK            0x04
#define ACM_CTRL_RI             0x08
#define ACM_CTRL_FRAMING        0x10
#define ACM_CTRL_PARITY         0x20
#define ACM_CTRL_OVERRUN        0x40
#endif

#include "linux/version.h"

#include "vizzini.h"

Running Linux kernel 3.4.9-2.fc16.x86_64

I would greatly appreciate any help in resolving the errors.

EDIT

It seems that usb_serial_register and usb_serial_deregister were never defined in my kernel’s API. However, usb_serial_register_drivers and usb_serial_deregister_drivers are. Below are the definitions:

int usb_serial_register(struct usb_serial_driver *driver);
void usb_serial_deregister(struct usb_serial_driver *device);
int usb_serial_register_drivers(struct usb_driver *udriver,
                                struct usb_serial_driver * const serial_drivers[]);
void usb_serial_deregister_drivers(struct usb_driver *udriver,
                                   struct usb_serial_driver * const serial_drivers[]);

Answer 1

The API inside the kernel (available header files, their contents, function prototypes (or if they exist in the first place), …) is not fixed (see Documentation/stable_api_nonsense.txt in your nearest Linux source if you are curious), so a driver can typically only be compiled for a rather narrow range of kernels. Check if the source is (roughly) contemporary with the kernel.

You should also check if a driver for that has already been included in the kernel, either as an official driver or in the staging area. Look around Linux USB to check for alternative drivers and other news. If nothing else helps, you should take a look at LWN‘s kernel pages (search there for functions you can’t find in the current source and discussion on replacement), probably after using something like cscope to create an index of your source (kernel and driver). Please do get in touch with the people responsible for this area, so they know you are groping around and perhaps give some pointers.