linux-kernel - Re: [PATCH 0/7] convert semaphore to mutex in struct class

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Date:	Thu, 10 Jan 2008 14:23:41 +0100
From:	Cornelia Huck <cornelia.huck@...ibm.com>
To:	Dave Young <hidave.darkstar@...il.com>
Cc:	Greg KH <gregkh@...e.de>,
	Stefan Richter <stefanr@...6.in-berlin.de>,
	James.Bottomley@...senpartnership.com, linux-scsi@...r.kernel.org,
	a.zummo@...ertech.it, peterz@...radead.org, cbou@...l.ru,
	linux-kernel@...r.kernel.org, David Brownell <david-b@...bell.net>,
	krh@...hat.com, stern@...land.harvard.edu,
	rtc-linux@...glegroups.com,
	spi-devel-general@...ts.sourceforge.net,
	linux1394-devel@...ts.sourceforge.net, dwmw2@...radead.org,
	davem@...emloft.net, jarkao2@...il.com
Subject: Re: [PATCH 0/7] convert semaphore to mutex in struct class

On Thu, 10 Jan 2008 17:48:43 +0800,
Dave Young <hidave.darkstar@...il.com> wrote:

Please add a kerneldoc comment for each of the new interfaces.

> +int class_for_each_device(struct class *class, void *data,
> +			   int (*fn)(struct device *, void *))
> +{
> +	struct device *dev;
> +	int error = 0;
> +
> +	if (!class)
> +		return -EINVAL;
> +	mutex_lock(&class->mutex);
> +	list_for_each_entry(dev, &class->devices, node) {
> +		error = fn(dev, data);

Hm, the equivalent _for_each_device() functions all elevate the
device's refcount while calling fn(). I wonder whether we want this
here as well?

> +		if (error)
> +			break;
> +	}
> +	mutex_unlock(&class->mutex);
> +
> +	return error;
> +}
> +EXPORT_SYMBOL_GPL(class_for_each_device);
> +
> +struct device *class_find_device(struct class *class, void *data,
> +				   int (*match)(struct device *, void *))
> +{
> +	struct device *dev;
> +
> +	if (!class)
> +		return NULL;
> +
> +	mutex_lock(&class->mutex);
> +	list_for_each_entry(dev, &class->devices, node)
> +		if (match(dev, data) && get_device(dev))

First get the reference and then drop it if the match function returns
0 to make this analogous to the other _find_device() functions?

> +			break;
> +	mutex_unlock(&class->mutex);
> +
> +	return dev;
> +}
> +EXPORT_SYMBOL_GPL(class_find_device);
> +
> +int class_for_each_child(struct class *class, void *data,
> +			   int (*fn)(struct class_device *, void *))

Haven't looked at the callers, but isn't it better to convert them to
use struct device instead so we don't need to introduce new
class_device api?

> +{
> +	struct class_device *dev;
> +	int error = 0;
> +
> +	if (!class)
> +		return -EINVAL;
> +	mutex_lock(&class->mutex);
> +	list_for_each_entry(dev, &class->children, node) {
> +		error = fn(dev, data);

Same comment as above concerning reference counts.

> +		if (error)
> +			break;
> +	}
> +	mutex_unlock(&class->mutex);
> +
> +	return error;
> +}
> +EXPORT_SYMBOL_GPL(class_for_each_child);
> +
> +struct class_device *class_find_child(struct class *class, void *data,
> +				   int (*match)(struct class_device *, void *))
> +{
> +	struct class_device *dev;
> +
> +	if (!class)
> +		return NULL;
> +
> +	mutex_lock(&class->mutex);
> +	list_for_each_entry(dev, &class->children, node)
> +		if (match(dev, data) && class_device_get(dev))

And here.

> +			break;
> +	mutex_unlock(&class->mutex);
> +
> +	return dev;
> +}
> +EXPORT_SYMBOL_GPL(class_find_child);
> +
--
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