[PATCH v4 2/6] block: Add Sed-opal library

[Scott Bauer]

> +struct opal_dev *alloc_opal_dev(struct request_queue *q)
> +{
> +	struct opal_dev *opal_dev;
> +	unsigned long dma_align;
> +	struct opal_cmd *cmd;
> +
> +	opal_dev = kzalloc(sizeof(*opal_dev), GFP_KERNEL);
> +	if (!opal_dev)
> +		return opal_dev;
> +
> +	cmd = &opal_dev->cmd;
> +	cmd->cmd = cmd->cmd_buf;
> +	cmd->resp = cmd->resp_buf;
> +
> +	dma_align = (queue_dma_alignment(q) | q->dma_pad_mask) + 1;
> +	cmd->cmd = (u8 *)round_up((uintptr_t)cmd->cmd, dma_align);
> +	cmd->resp = (u8 *)round_up((uintptr_t)cmd->resp, dma_align);
> +
> +	INIT_LIST_HEAD(&opal_dev->unlk_lst);
> +	opal_dev->state = 0;
> +
> +	mutex_init(&opal_dev->dev_lock);
> +
> +	return opal_dev;
> +
> +}
> +EXPORT_SYMBOL(alloc_opal_dev);

Internally we've been discussing this function. We don't like the requirement
that we have to pass in a request_queue just to allocate an opal dev.

We have a few ideas and wanted to toss them out here and see if anyone has
one they love or one they hate.

So Idea one:

Pass in the alignment insetead of the request_queue. This pushes the burden
onto the driver calling alloc_opal_dev instead of the opal core. It also removes
the requirement of passing in a request_queue to something we think should be
agnostic to any blocklayer/lower level structures/knowledge.


Idea two:

Just let alloc_opal_dev kzalloc normally and do no alignment. It would then
be up to the drivers to move the data from the buffer to a bounce buffer,
that is aligned, in the send/recv functions before sending down to the controller.

Both are easy to implement but we wanted to see if anyone had other ideas or liked
one over the other.