Commit 3cc50d07 authored by Lukas Wunner's avatar Lukas Wunner Committed by Greg Kroah-Hartman
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driver core: Add device_show_string() helper for sysfs attributes 



For drivers wishing to expose an unsigned long, int or bool at a static
memory location in sysfs, the driver core provides ready-made helpers
such as device_show_ulong() to be used as ->show() callback.

Some drivers need to expose a string and so far they all provide their
own ->show() implementation.  arch/powerpc/perf/hv-24x7.c went so far
as to create a device_show_string() helper but kept it private.

Make it public for reuse by other drivers.  The pattern seems to be
sufficiently frequent to merit a public helper.

Add a DEVICE_STRING_ATTR_RO() macro in line with the existing
DEVICE_ULONG_ATTR() and similar macros to ease declaration of string
attributes.

Signed-off-by: default avatarLukas Wunner <lukas@wunner.de>
Acked-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/2e3eaaf2600bb55c0415c23ba301e809403a7aa2.1713608122.git.lukas@wunner.de


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e5019b14

arch/powerpc/perf/hv-24x7.c

+0 −10
Original line number Diff line number Diff line
@@ -425,16 +425,6 @@ static char *memdup_to_str(char *maybe_str, int max_len, gfp_t gfp) 
	return kasprintf(gfp, "%.*s", max_len, maybe_str);

}



static ssize_t device_show_string(struct device *dev,

		struct device_attribute *attr, char *buf)

{

	struct dev_ext_attribute *d;



	d = container_of(attr, struct dev_ext_attribute, attr);



	return sprintf(buf, "%s\n", (char *)d->var);

}



static ssize_t cpumask_show(struct device *dev,

			    struct device_attribute *attr, char *buf)

{

drivers/base/core.c

+9 −0
Original line number Diff line number Diff line
@@ -2538,6 +2538,15 @@ ssize_t device_show_bool(struct device *dev, struct device_attribute *attr, 
}

EXPORT_SYMBOL_GPL(device_show_bool);



ssize_t device_show_string(struct device *dev,

			   struct device_attribute *attr, char *buf)

{

	struct dev_ext_attribute *ea = to_ext_attr(attr);



	return sysfs_emit(buf, "%s\n", (char *)ea->var);

}

EXPORT_SYMBOL_GPL(device_show_string);



/**

 * device_release - free device structure.

 * @kobj: device's kobject.

include/linux/device.h

+15 −0
Original line number Diff line number Diff line
@@ -132,6 +132,8 @@ ssize_t device_show_bool(struct device *dev, struct device_attribute *attr, 
			char *buf);

ssize_t device_store_bool(struct device *dev, struct device_attribute *attr,

			 const char *buf, size_t count);

ssize_t device_show_string(struct device *dev, struct device_attribute *attr,

			   char *buf);



/**

 * DEVICE_ATTR - Define a device attribute.
@@ -251,6 +253,19 @@ ssize_t device_store_bool(struct device *dev, struct device_attribute *attr, 
	struct dev_ext_attribute dev_attr_##_name = \

		{ __ATTR(_name, _mode, device_show_bool, device_store_bool), &(_var) }



/**

 * DEVICE_STRING_ATTR_RO - Define a device attribute backed by a r/o string.

 * @_name: Attribute name.

 * @_mode: File mode.

 * @_var: Identifier of string.

 *

 * Like DEVICE_ULONG_ATTR(), but @_var is a string. Because the length of the

 * string allocation is unknown, the attribute must be read-only.

 */

#define DEVICE_STRING_ATTR_RO(_name, _mode, _var) \

	struct dev_ext_attribute dev_attr_##_name = \

		{ __ATTR(_name, (_mode) & ~0222, device_show_string, NULL), (_var) }



#define DEVICE_ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store) \

	struct device_attribute dev_attr_##_name =		\

		__ATTR_IGNORE_LOCKDEP(_name, _mode, _show, _store)