linux-kernel - Re: [PATCH v2 5/7] soc: qcom: smd: Support opening additional channels

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Date:	Wed, 14 Oct 2015 13:53:58 -0700
From:	Bjorn Andersson <bjorn.andersson@...ymobile.com>
To:	yfw <fengwei.yin@...aro.org>
CC:	Andy Gross <agross@...eaurora.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	"linux-soc@...r.kernel.org" <linux-soc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Subject: Re: [PATCH v2 5/7] soc: qcom: smd: Support opening additional
 channels

On Wed 14 Oct 08:09 PDT 2015, yfw wrote:

> Hi Bjorn,
> 
> On 2015/10/10 4:48, Bjorn Andersson wrote:
> > With the qcom_smd_open_channel() API we allow SMD devices to open
> > additional SMD channels, to allow implementation of multi-channel SMD
> > devices - like Bluetooth.
> >
> > Channels are opened from the same edge as the calling SMD device is tied
> > to.
> >
[..]
> > +/**
> > + * qcom_smd_open_channel() - claim additional channels on the same edge
> > + * @sdev:	smd_device handle
> > + * @name:	channel name
> > + * @cb:		callback method to use for incoming data
> > + *
> > + * Returns a channel handle on success, or -EPROBE_DEFER if the channel isn't
> > + * ready.
> > + */
> > +struct qcom_smd_channel *qcom_smd_open_channel(struct qcom_smd_device *sdev,
> > +					       const char *name,
> > +					       qcom_smd_cb_t cb)
> > +{
> > +	struct qcom_smd_channel *channel;
> > +	struct qcom_smd_edge *edge = sdev->channel->edge;
> > +	int ret;
> > +
> > +	/* Wait up to HZ for the channel to appear */
> > +	ret = wait_event_interruptible_timeout(edge->new_channel_event,
> > +			(channel = qcom_smd_find_channel(edge, name)) != NULL,
> > +			HZ);
> > +	if (!ret)
> > +		return ERR_PTR(-ETIMEDOUT);
> > +
> > +	if (channel->state != SMD_CHANNEL_CLOSED) {
> > +		dev_err(&sdev->dev, "channel %s is busy\n", channel->name);
> > +		return ERR_PTR(-EBUSY);
> > +	}
> > +
> > +	channel->qsdev = sdev;
> > +	ret = qcom_smd_channel_open(channel, cb);
> > +	if (ret) {
> > +		channel->qsdev = NULL;
> > +		return ERR_PTR(ret);
> > +	}
> > +
> > +	/*
> > +	 * Append the list of channel to the channels associated with the sdev
> > +	 */
> > +	list_add_tail(&channel->dev_list, &sdev->channel->dev_list);
> > +
> > +	return channel;
> > +}
> > +EXPORT_SYMBOL(qcom_smd_open_channel);
> > +
> Do we need qcom_smd_close_channel API here?
> 

On success the channel is associated with the qcom_smd_device, which
tears down all associated channels on destruction.

I have not yet seen any reason for decoupling the life cycle of a
channel further from the device (in most cases it's very must 1:1).

But I will update the comment above to clarify this fact, thanks!

Regards,
Bjorn
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