arch/um/drivers/xterm_kern.c

Source file repositories/reference/linux-study-clean/arch/um/drivers/xterm_kern.c

File Facts

System
Linux kernel
Corpus path
arch/um/drivers/xterm_kern.c
Extension
.c
Size
1712 bytes
Lines
84
Domain
Architecture Layer
Bucket
arch/um
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

struct xterm_wait {
	struct completion ready;
	int fd;
	int pid;
	int new_fd;
};

static irqreturn_t xterm_interrupt(int irq, void *data)
{
	struct xterm_wait *xterm = data;
	int fd = -1, n_fds = 1;
	ssize_t ret;

	ret = os_rcv_fd_msg(xterm->fd, &fd, n_fds,
			    &xterm->pid, sizeof(xterm->pid));
	if (ret == -EAGAIN)
		return IRQ_NONE;

	if (ret < 0)
		fd = ret;
	else if (ret != sizeof(xterm->pid))
		fd = -EMSGSIZE;

	xterm->new_fd = fd;
	complete(&xterm->ready);

	return IRQ_HANDLED;
}

int xterm_fd(int socket, int *pid_out)
{
	struct xterm_wait *data;
	int err, ret;

	data = kmalloc_obj(*data);
	if (data == NULL) {
		printk(KERN_ERR "xterm_fd : failed to allocate xterm_wait\n");
		return -ENOMEM;
	}

	/* This is a locked semaphore... */
	*data = ((struct xterm_wait) { .fd 		= socket,
				       .pid 		= -1,
				       .new_fd	 	= -1 });
	init_completion(&data->ready);

	err = um_request_irq(XTERM_IRQ, socket, IRQ_READ, xterm_interrupt,
			     IRQF_SHARED, "xterm", data);
	if (err < 0) {
		printk(KERN_ERR "xterm_fd : failed to get IRQ for xterm, "
		       "err = %d\n",  err);
		ret = err;
		goto out;
	}

	/* ... so here we wait for an xterm interrupt.
	 *
	 * XXX Note, if the xterm doesn't work for some reason (eg. DISPLAY
	 * isn't set) this will hang... */
	wait_for_completion(&data->ready);

	um_free_irq(XTERM_IRQ, data);

	ret = data->new_fd;
	*pid_out = data->pid;
 out:
	kfree(data);

	return ret;
}

Annotation

Implementation Notes