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Date: Sun, 26 Apr 2015 20:26:28 +0100
From: Jonathan Cameron <jic23@kernel.org>
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To: Daniel Baluta <daniel.baluta@intel.com>
CC: jlbec@evilplan.org, lars@metafoo.de, knaack.h@gmx.de,
        linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org,
        octavian.purdila@intel.com, pebolle@tiscali.nl,
        patrick.porlan@intel.com, adriana.reus@intel.com,
        constantin.musca@intel.com, marten@intuitiveaerial.com
Subject: Re: [PATCH v4 2/4] iio: core: Introduce IIO configfs support
References: <1429538563-23430-1-git-send-email-daniel.baluta@intel.com> <1429538563-23430-3-git-send-email-daniel.baluta@intel.com>
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On 20/04/15 15:02, Daniel Baluta wrote:
> This creates an IIO configfs subystem named "iio", with a default "triggers"
> group.
> 
> Triggers group is used for handling software triggers. To create a new software
> trigger one must create a directory inside the trigger directory.
> 
> Software trigger name MUST follow the following convention:
> 	* <trigger-type>-<trigger-name>
> Where:
> 	* <trigger_type>, specifies the interrupt source (e.g: hrtimer)
> 	* <trigger-name>, specifies the IIO device trigger name
> 
> Failing to follow this convention will result in an directory creation error.
> 
> E.g, assuming that hrtimer trigger type is registered with IIO software
> trigger core:
> 
> $ mkdir /config/iio/triggers/hrtimer-instance1
> 
> Signed-off-by: Daniel Baluta <daniel.baluta@intel.com>
Looks good. Couple of little comments inline.

Jonathan
> ---
>  drivers/iio/Kconfig                 |   8 +++
>  drivers/iio/Makefile                |   1 +
>  drivers/iio/industrialio-configfs.c | 117 ++++++++++++++++++++++++++++++++++++
>  3 files changed, 126 insertions(+)
>  create mode 100644 drivers/iio/industrialio-configfs.c
> 
> diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
> index de7f1d9..c310156 100644
> --- a/drivers/iio/Kconfig
> +++ b/drivers/iio/Kconfig
> @@ -18,6 +18,14 @@ config IIO_BUFFER
>  	  Provide core support for various buffer based data
>  	  acquisition methods.
>  
> +config IIO_CONFIGFS
> +	tristate "Enable IIO configuration via configfs"
> +	select CONFIGFS_FS
> +	help
> +	  This allows configuring various IIO bits through configfs
> +	  (e.g. software triggers). For more info see
> +	  Documentation/iio/iio_configfs.txt.
> +
>  if IIO_BUFFER
>  
>  config IIO_BUFFER_CB
> diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
> index df87975..31aead3 100644
> --- a/drivers/iio/Makefile
> +++ b/drivers/iio/Makefile
> @@ -10,6 +10,7 @@ industrialio-$(CONFIG_IIO_SW_TRIGGER) += industrialio-sw-trigger.o
>  industrialio-$(CONFIG_IIO_BUFFER_CB) += buffer_cb.o
>  
>  obj-$(CONFIG_IIO_TRIGGERED_BUFFER) += industrialio-triggered-buffer.o
> +obj-$(CONFIG_IIO_CONFIGFS) += industrialio-configfs.o
>  obj-$(CONFIG_IIO_KFIFO_BUF) += kfifo_buf.o
>  
>  obj-y += accel/
> diff --git a/drivers/iio/industrialio-configfs.c b/drivers/iio/industrialio-configfs.c
> new file mode 100644
> index 0000000..0361434
> --- /dev/null
> +++ b/drivers/iio/industrialio-configfs.c
> @@ -0,0 +1,117 @@
> +/*
> + * Industrial I/O configfs bits
> + *
> + * Copyright (c) 2015 Intel Corporation
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License version 2 as published by
> + * the Free Software Foundation.
> + */
> +
> +#include <linux/configfs.h>
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/kmod.h>
> +#include <linux/slab.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/sw_trigger.h>
> +
> +#define MAX_NAME_LEN 32
Strikes me as perhaps a little short given we want to allow 'almost' arbitary names for the triggers.
> +
> +static struct config_group *trigger_make_group(struct config_group *group,
> +					       const char *name)
> +{
> +	char *type_name;
> +	char *trigger_name;
> +	char buf[MAX_NAME_LEN];
> +	struct iio_sw_trigger *t;
> +
> +	snprintf(buf, MAX_NAME_LEN, "%s", name);
> +
> +	/* group name should have the form <trigger-type>-<trigger-name> */
> +	type_name = buf;
> +	trigger_name = strchr(buf, '-');
> +	if (!trigger_name) {
> +		pr_err("Unable to locate '-' in %s. Use <type>-<name>.\n", buf);
> +		return ERR_PTR(-EINVAL);
> +	}
> +
> +	/* replace - with \0, this nicely separates the two strings */
> +	*trigger_name = '\0';
Dirty trick, but I like it.
> +	trigger_name++;
> +
> +	t = iio_sw_trigger_create(type_name, trigger_name);
> +	if (IS_ERR(t))
> +		return ERR_CAST(t);
> +
> +	config_item_set_name(&t->group.cg_item, name);
> +
> +	return &t->group;
> +}
> +
> +static void trigger_drop_group(struct config_group *group,
> +			       struct config_item *item)
> +{
> +	struct iio_sw_trigger *t = to_iio_sw_trigger(item);
> +
> +	if (t)
> +		iio_sw_trigger_destroy(t);
> +	config_item_put(item);
> +}
> +
> +static struct configfs_group_operations triggers_ops = {
> +	.make_group	= &trigger_make_group,
> +	.drop_item	= &trigger_drop_group,
> +};
> +
> +static struct config_item_type iio_triggers_group_type = {
> +	.ct_group_ops = &triggers_ops,
> +	.ct_owner       = THIS_MODULE,
> +};
> +
> +static struct config_group iio_triggers_group = {
> +	.cg_item = {
> +		.ci_namebuf = "triggers",
> +		.ci_type = &iio_triggers_group_type,
> +	},
> +};
> +
> +static struct config_group *iio_root_default_groups[] = {
> +	&iio_triggers_group,
> +	NULL
> +};
> +
> +static struct config_item_type iio_root_group_type = {
> +	.ct_owner       = THIS_MODULE,
> +};
> +
> +static struct configfs_subsystem iio_configfs_subsys = {
> +	.su_group = {
> +		.cg_item = {
> +			.ci_namebuf = "iio",
> +			.ci_type = &iio_root_group_type,
> +		},
> +		.default_groups = iio_root_default_groups,
> +	},
> +	.su_mutex = __MUTEX_INITIALIZER(iio_configfs_subsys.su_mutex),
> +};
> +
> +static int __init iio_configfs_init(void)
> +{
> +	config_group_init(&iio_triggers_group);
> +	config_group_init(&iio_configfs_subsys.su_group);
> +
> +	return configfs_register_subsystem(&iio_configfs_subsys);
> +}
> +module_init(iio_configfs_init);
> +
> +static void __exit iio_configfs_exit(void)
> +{
> +	configfs_unregister_subsystem(&iio_configfs_subsys);
> +}
> +module_exit(iio_configfs_exit);
> +
> +MODULE_AUTHOR("Daniel Baluta <daniel.baluta@intel.com>");
> +MODULE_DESCRIPTION("Industrial I/O configfs support");
> +MODULE_LICENSE("GPL v2");
>