linux-kernel - Re: [PATCH V4 3/6] slimbus: Add messaging APIs to slimbus framework

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Message-ID: <20160305051325.GD18327@sirena.org.uk>
Date:	Sat, 5 Mar 2016 14:13:25 +0900
From:	Mark Brown <broonie@...nel.org>
To:	Sagar Dharia <sdharia@...eaurora.org>
Cc:	gregkh@...uxfoundation.org, bp@...e.de, poeschel@...onage.de,
	treding@...dia.com, gong.chen@...ux.intel.com,
	andreas.noever@...il.com, alan@...ux.intel.com,
	mathieu.poirier@...aro.org, daniel@...ll.ch, oded.gabbay@....com,
	jkosina@...e.cz, sharon.dvir1@...l.huji.ac.il, joe@...ches.com,
	davem@...emloft.net, james.hogan@...tec.com,
	michael.opdenacker@...e-electrons.com, daniel.thompson@...aro.org,
	robh+dt@...nel.org, pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	kheitke@...ience.com, mlocke@...eaurora.org, agross@...eaurora.org,
	linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH V4 3/6] slimbus: Add messaging APIs to slimbus framework

On Sat, Feb 06, 2016 at 11:44:22AM -0700, Sagar Dharia wrote:

> +	spin_lock_irqsave(&ctrl->txn_lock, flags);
> +	msg = ctrl->tid_tbl[tid];
> +	if (msg == NULL || msg->rbuf == NULL) {
> +		spin_unlock_irqrestore(&ctrl->txn_lock, flags);
> +		dev_err(&ctrl->dev, "Got response to invalid TID:%d, len:%d\n",
> +				tid, len);
> +		return;
> +	}
> +	memcpy(msg->rbuf, reply, len);
> +	ctrl->tid_tbl[tid] = NULL;
> +	if (msg->comp_cb)
> +		msg->comp_cb(msg->ctx, 0);
> +	spin_unlock_irqrestore(&ctrl->txn_lock, flags);

Do we need to hold the lock for so long (especially with things like the
memcpy())?  As far as I can tell we only need the lock for this:

> +	msg = ctrl->tid_tbl[tid];
> +	ctrl->tid_tbl[tid] = NULL;

> +	if (mc == SLIM_MSG_MC_REQUEST_CHANGE_VALUE ||
> +		mc == SLIM_MSG_MC_CHANGE_VALUE ||
> +		mc == SLIM_MSG_MC_REQUEST_CLEAR_INFORMATION ||
> +		mc == SLIM_MSG_MC_CLEAR_INFORMATION)
> +		txn->rl += msg->num_bytes;

A switch statement might be nicer here.

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