[openib-general] Proposed device enumeration & async event APIs

[Roland Dreier]

    Fabian> Do you plan on having an allocation per client, or having
    Fabian> an array of allocations that you grow dynamically as
    Fabian> needed?  I would think the array would be beneficial since
    Fabian> you end up with fewer allocations.  It does require
    Fabian> synchronization and a counter to keep track of the array
    Fabian> size.  Resize would then just do a malloc, copy, and free.

I allocate per client per device.  I just wanted to do the dumbest,
simplest possible thing, given that the number of clients and devices
are probably going to be in single digits on almost all machines.
However, now that we have an API defined, we can make whatever changes
to the implementation are required later painlessly.

If you're curious, here's the actual implementation:

	void *ib_get_client_data(struct ib_device *device, struct ib_client *client)
	{
		struct ib_client_data *context;
		void *ret = NULL;
		unsigned long flags;

		spin_lock_irqsave(&device->client_data_lock, flags);
		list_for_each_entry(context, &device->client_data_list, list)
			if (context->client == client) {
				ret = context->data;
				break;
			}
		spin_unlock_irqrestore(&device->client_data_lock, flags);

		return ret;
	}

	int ib_set_client_data(struct ib_device *device, struct ib_client *client,
			       void *data)
	{
		struct ib_client_data *context;
		int ret = 0;
		unsigned long flags;

		spin_lock_irqsave(&device->client_data_lock, flags);
		list_for_each_entry(context, &device->client_data_list, list)
			if (context->client == client) {
				context->data = data;
				spin_unlock_irqrestore(&device->client_data_lock, flags);
				return 0;
			}

		spin_unlock_irqrestore(&device->client_data_lock, flags);
		context = kmalloc(sizeof *context, GFP_KERNEL);
		if (!context)
			return -ENOMEM;

		context->client = client;
		context->data   = data;

		spin_lock_irqsave(&device->client_data_lock, flags);
		list_add(&context->list, &device->client_data_list);
		spin_unlock_irqrestore(&device->client_data_lock, flags);

		return 0;
	}