File access within the kernel is not very difficult. But make sure you thought it trough; For example, don't use configuration-files, a sysctl-variable is a much better and cleaner solution. Loading firmware is probably also not a good reason for reading files. There are cases where you definitly want to access a file (kHTTPd and knfsd are two of them), and although the code is there, I have not been able to find a simple example of how to do it. So here comes my example (note: It doesn't do any kernel-locking to keep the example simple):

void ReadFile(char *Filename, int StartPos)
{
	struct file 	*filp;
	char		*Buffer;
	mm_segment_t	oldfs;
	int		BytesRead;

	Buffer = kmalloc(4096,GFP_KERNEL);
	if (Buffer==NULL) 
		return;
	
	filp = filp_open(Filename,00,O_RDONLY);
	if (IS_ERR(filp)||(filp==NULL))
		return;  /* Or do something else */

	if (filp->f_op->read==NULL)
		return;  /* File(system) doesn't allow reads */

	/* Now read 4096 bytes from postion "StartPos" */
	filp->f_pos = StartPos;
	oldfs = get_fs();
	set_fs(KERNEL_DS);
	BytesRead = filp->f_op->read(filp,Buffer,4096,&filp->f_pos);
	set_fs(oldfs);

	/* Close the file */
	fput(filp);

}

The example copies the data from the buffercache to the kernel(thread)s private memory. If the copy is to costly for you, it is possible to use the buffercache directly. I will not give an example of this, as this is very complex, version-dependend and well documented in do_generic_file_read(...) in mm/filemap.c.