static int um_pci_send_cmd()

in drivers/virt-pci.c [66:169]

• 86 lines of code
• 23 McCabe index (conditional complexity)

static int um_pci_send_cmd(struct um_pci_device *dev,
			   struct virtio_pcidev_msg *cmd,
			   unsigned int cmd_size,
			   const void *extra, unsigned int extra_size,
			   void *out, unsigned int out_size)
{
	struct scatterlist out_sg, extra_sg, in_sg;
	struct scatterlist *sgs_list[] = {
		[0] = &out_sg,
		[1] = extra ? &extra_sg : &in_sg,
		[2] = extra ? &in_sg : NULL,
	};
	struct um_pci_message_buffer *buf;
	int delay_count = 0;
	int ret, len;
	bool posted;

	if (WARN_ON(cmd_size < sizeof(*cmd) || cmd_size > sizeof(*buf)))
		return -EINVAL;

	switch (cmd->op) {
	case VIRTIO_PCIDEV_OP_CFG_WRITE:
	case VIRTIO_PCIDEV_OP_MMIO_WRITE:
	case VIRTIO_PCIDEV_OP_MMIO_MEMSET:
		/* in PCI, writes are posted, so don't wait */
		posted = !out;
		WARN_ON(!posted);
		break;
	default:
		posted = false;
		break;
	}

	buf = get_cpu_var(um_pci_msg_bufs);
	memcpy(buf, cmd, cmd_size);

	if (posted) {
		u8 *ncmd = kmalloc(cmd_size + extra_size, GFP_ATOMIC);

		if (ncmd) {
			memcpy(ncmd, cmd, cmd_size);
			if (extra)
				memcpy(ncmd + cmd_size, extra, extra_size);
			cmd = (void *)ncmd;
			cmd_size += extra_size;
			extra = NULL;
			extra_size = 0;
		} else {
			/* try without allocating memory */
			posted = false;
			cmd = (void *)buf;
		}
	} else {
		cmd = (void *)buf;
	}

	sg_init_one(&out_sg, cmd, cmd_size);
	if (extra)
		sg_init_one(&extra_sg, extra, extra_size);
	if (out)
		sg_init_one(&in_sg, out, out_size);

	/* add to internal virtio queue */
	ret = virtqueue_add_sgs(dev->cmd_vq, sgs_list,
				extra ? 2 : 1,
				out ? 1 : 0,
				posted ? cmd : HANDLE_NO_FREE(cmd),
				GFP_ATOMIC);
	if (ret)
		goto out;

	if (posted) {
		virtqueue_kick(dev->cmd_vq);
		ret = 0;
		goto out;
	}

	/* kick and poll for getting a response on the queue */
	set_bit(UM_PCI_STAT_WAITING, &dev->status);
	virtqueue_kick(dev->cmd_vq);

	while (1) {
		void *completed = virtqueue_get_buf(dev->cmd_vq, &len);

		if (completed == HANDLE_NO_FREE(cmd))
			break;

		if (completed && !HANDLE_IS_NO_FREE(completed))
			kfree(completed);

		if (WARN_ONCE(virtqueue_is_broken(dev->cmd_vq) ||
			      ++delay_count > UM_VIRT_PCI_MAXDELAY,
			      "um virt-pci delay: %d", delay_count)) {
			ret = -EIO;
			break;
		}
		udelay(1);
	}
	clear_bit(UM_PCI_STAT_WAITING, &dev->status);

out:
	put_cpu_var(um_pci_msg_bufs);
	return ret;
}