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cdb4f26a63
Now that all in-kernel users of default_attrs for the kobj_type are gone and converted to properly use the default_groups pointer instead, it can be safely removed. There is one standard way to create sysfs files in a kobj_type, and not two like before, causing confusion as to which should be used. Cc: "Rafael J. Wysocki" <rafael@kernel.org> Link: https://lore.kernel.org/r/20220106133151.607703-1-gregkh@linuxfoundation.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
773 lines
19 KiB
C
773 lines
19 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* fs/sysfs/file.c - sysfs regular (text) file implementation
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*
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* Copyright (c) 2001-3 Patrick Mochel
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* Copyright (c) 2007 SUSE Linux Products GmbH
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* Copyright (c) 2007 Tejun Heo <teheo@suse.de>
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*
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* Please see Documentation/filesystems/sysfs.rst for more information.
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*/
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#include <linux/module.h>
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#include <linux/kobject.h>
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#include <linux/slab.h>
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#include <linux/list.h>
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#include <linux/mutex.h>
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#include <linux/seq_file.h>
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#include <linux/mm.h>
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#include "sysfs.h"
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/*
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* Determine ktype->sysfs_ops for the given kernfs_node. This function
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* must be called while holding an active reference.
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*/
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static const struct sysfs_ops *sysfs_file_ops(struct kernfs_node *kn)
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{
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struct kobject *kobj = kn->parent->priv;
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if (kn->flags & KERNFS_LOCKDEP)
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lockdep_assert_held(kn);
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return kobj->ktype ? kobj->ktype->sysfs_ops : NULL;
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}
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/*
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* Reads on sysfs are handled through seq_file, which takes care of hairy
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* details like buffering and seeking. The following function pipes
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* sysfs_ops->show() result through seq_file.
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*/
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static int sysfs_kf_seq_show(struct seq_file *sf, void *v)
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{
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struct kernfs_open_file *of = sf->private;
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struct kobject *kobj = of->kn->parent->priv;
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const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
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ssize_t count;
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char *buf;
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if (WARN_ON_ONCE(!ops->show))
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return -EINVAL;
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/* acquire buffer and ensure that it's >= PAGE_SIZE and clear */
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count = seq_get_buf(sf, &buf);
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if (count < PAGE_SIZE) {
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seq_commit(sf, -1);
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return 0;
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}
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memset(buf, 0, PAGE_SIZE);
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count = ops->show(kobj, of->kn->priv, buf);
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if (count < 0)
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return count;
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/*
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* The code works fine with PAGE_SIZE return but it's likely to
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* indicate truncated result or overflow in normal use cases.
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*/
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if (count >= (ssize_t)PAGE_SIZE) {
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printk("fill_read_buffer: %pS returned bad count\n",
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ops->show);
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/* Try to struggle along */
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count = PAGE_SIZE - 1;
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}
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seq_commit(sf, count);
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return 0;
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}
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static ssize_t sysfs_kf_bin_read(struct kernfs_open_file *of, char *buf,
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size_t count, loff_t pos)
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{
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struct bin_attribute *battr = of->kn->priv;
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struct kobject *kobj = of->kn->parent->priv;
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loff_t size = file_inode(of->file)->i_size;
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if (!count)
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return 0;
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if (size) {
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if (pos >= size)
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return 0;
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if (pos + count > size)
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count = size - pos;
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}
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if (!battr->read)
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return -EIO;
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return battr->read(of->file, kobj, battr, buf, pos, count);
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}
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/* kernfs read callback for regular sysfs files with pre-alloc */
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static ssize_t sysfs_kf_read(struct kernfs_open_file *of, char *buf,
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size_t count, loff_t pos)
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{
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const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
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struct kobject *kobj = of->kn->parent->priv;
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ssize_t len;
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/*
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* If buf != of->prealloc_buf, we don't know how
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* large it is, so cannot safely pass it to ->show
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*/
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if (WARN_ON_ONCE(buf != of->prealloc_buf))
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return 0;
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len = ops->show(kobj, of->kn->priv, buf);
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if (len < 0)
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return len;
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if (pos) {
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if (len <= pos)
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return 0;
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len -= pos;
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memmove(buf, buf + pos, len);
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}
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return min_t(ssize_t, count, len);
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}
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/* kernfs write callback for regular sysfs files */
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static ssize_t sysfs_kf_write(struct kernfs_open_file *of, char *buf,
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size_t count, loff_t pos)
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{
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const struct sysfs_ops *ops = sysfs_file_ops(of->kn);
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struct kobject *kobj = of->kn->parent->priv;
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if (!count)
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return 0;
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return ops->store(kobj, of->kn->priv, buf, count);
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}
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/* kernfs write callback for bin sysfs files */
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static ssize_t sysfs_kf_bin_write(struct kernfs_open_file *of, char *buf,
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size_t count, loff_t pos)
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{
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struct bin_attribute *battr = of->kn->priv;
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struct kobject *kobj = of->kn->parent->priv;
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loff_t size = file_inode(of->file)->i_size;
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if (size) {
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if (size <= pos)
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return -EFBIG;
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count = min_t(ssize_t, count, size - pos);
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}
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if (!count)
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return 0;
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if (!battr->write)
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return -EIO;
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return battr->write(of->file, kobj, battr, buf, pos, count);
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}
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static int sysfs_kf_bin_mmap(struct kernfs_open_file *of,
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struct vm_area_struct *vma)
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{
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struct bin_attribute *battr = of->kn->priv;
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struct kobject *kobj = of->kn->parent->priv;
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return battr->mmap(of->file, kobj, battr, vma);
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}
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static int sysfs_kf_bin_open(struct kernfs_open_file *of)
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{
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struct bin_attribute *battr = of->kn->priv;
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if (battr->f_mapping)
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of->file->f_mapping = battr->f_mapping();
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return 0;
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}
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void sysfs_notify(struct kobject *kobj, const char *dir, const char *attr)
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{
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struct kernfs_node *kn = kobj->sd, *tmp;
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if (kn && dir)
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kn = kernfs_find_and_get(kn, dir);
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else
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kernfs_get(kn);
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if (kn && attr) {
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tmp = kernfs_find_and_get(kn, attr);
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kernfs_put(kn);
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kn = tmp;
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}
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if (kn) {
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kernfs_notify(kn);
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kernfs_put(kn);
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}
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}
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EXPORT_SYMBOL_GPL(sysfs_notify);
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static const struct kernfs_ops sysfs_file_kfops_empty = {
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};
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static const struct kernfs_ops sysfs_file_kfops_ro = {
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.seq_show = sysfs_kf_seq_show,
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};
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static const struct kernfs_ops sysfs_file_kfops_wo = {
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.write = sysfs_kf_write,
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};
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static const struct kernfs_ops sysfs_file_kfops_rw = {
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.seq_show = sysfs_kf_seq_show,
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.write = sysfs_kf_write,
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};
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static const struct kernfs_ops sysfs_prealloc_kfops_ro = {
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.read = sysfs_kf_read,
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.prealloc = true,
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};
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static const struct kernfs_ops sysfs_prealloc_kfops_wo = {
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.write = sysfs_kf_write,
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.prealloc = true,
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};
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static const struct kernfs_ops sysfs_prealloc_kfops_rw = {
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.read = sysfs_kf_read,
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.write = sysfs_kf_write,
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.prealloc = true,
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};
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static const struct kernfs_ops sysfs_bin_kfops_ro = {
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.read = sysfs_kf_bin_read,
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};
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static const struct kernfs_ops sysfs_bin_kfops_wo = {
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.write = sysfs_kf_bin_write,
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};
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static const struct kernfs_ops sysfs_bin_kfops_rw = {
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.read = sysfs_kf_bin_read,
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.write = sysfs_kf_bin_write,
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};
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static const struct kernfs_ops sysfs_bin_kfops_mmap = {
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.read = sysfs_kf_bin_read,
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.write = sysfs_kf_bin_write,
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.mmap = sysfs_kf_bin_mmap,
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.open = sysfs_kf_bin_open,
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};
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int sysfs_add_file_mode_ns(struct kernfs_node *parent,
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const struct attribute *attr, umode_t mode, kuid_t uid,
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kgid_t gid, const void *ns)
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{
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struct kobject *kobj = parent->priv;
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const struct sysfs_ops *sysfs_ops = kobj->ktype->sysfs_ops;
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struct lock_class_key *key = NULL;
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const struct kernfs_ops *ops = NULL;
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struct kernfs_node *kn;
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/* every kobject with an attribute needs a ktype assigned */
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if (WARN(!sysfs_ops, KERN_ERR
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"missing sysfs attribute operations for kobject: %s\n",
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kobject_name(kobj)))
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return -EINVAL;
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if (mode & SYSFS_PREALLOC) {
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if (sysfs_ops->show && sysfs_ops->store)
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ops = &sysfs_prealloc_kfops_rw;
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else if (sysfs_ops->show)
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ops = &sysfs_prealloc_kfops_ro;
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else if (sysfs_ops->store)
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ops = &sysfs_prealloc_kfops_wo;
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} else {
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if (sysfs_ops->show && sysfs_ops->store)
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ops = &sysfs_file_kfops_rw;
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else if (sysfs_ops->show)
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ops = &sysfs_file_kfops_ro;
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else if (sysfs_ops->store)
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ops = &sysfs_file_kfops_wo;
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}
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if (!ops)
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ops = &sysfs_file_kfops_empty;
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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if (!attr->ignore_lockdep)
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key = attr->key ?: (struct lock_class_key *)&attr->skey;
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#endif
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kn = __kernfs_create_file(parent, attr->name, mode & 0777, uid, gid,
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PAGE_SIZE, ops, (void *)attr, ns, key);
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if (IS_ERR(kn)) {
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if (PTR_ERR(kn) == -EEXIST)
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sysfs_warn_dup(parent, attr->name);
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return PTR_ERR(kn);
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}
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return 0;
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}
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int sysfs_add_bin_file_mode_ns(struct kernfs_node *parent,
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const struct bin_attribute *battr, umode_t mode,
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kuid_t uid, kgid_t gid, const void *ns)
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{
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const struct attribute *attr = &battr->attr;
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struct lock_class_key *key = NULL;
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const struct kernfs_ops *ops;
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struct kernfs_node *kn;
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if (battr->mmap)
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ops = &sysfs_bin_kfops_mmap;
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else if (battr->read && battr->write)
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ops = &sysfs_bin_kfops_rw;
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else if (battr->read)
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ops = &sysfs_bin_kfops_ro;
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else if (battr->write)
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ops = &sysfs_bin_kfops_wo;
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else
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ops = &sysfs_file_kfops_empty;
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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if (!attr->ignore_lockdep)
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key = attr->key ?: (struct lock_class_key *)&attr->skey;
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#endif
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kn = __kernfs_create_file(parent, attr->name, mode & 0777, uid, gid,
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battr->size, ops, (void *)attr, ns, key);
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if (IS_ERR(kn)) {
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if (PTR_ERR(kn) == -EEXIST)
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sysfs_warn_dup(parent, attr->name);
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return PTR_ERR(kn);
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}
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return 0;
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}
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/**
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* sysfs_create_file_ns - create an attribute file for an object with custom ns
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* @kobj: object we're creating for
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* @attr: attribute descriptor
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* @ns: namespace the new file should belong to
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*/
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int sysfs_create_file_ns(struct kobject *kobj, const struct attribute *attr,
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const void *ns)
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{
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kuid_t uid;
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kgid_t gid;
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if (WARN_ON(!kobj || !kobj->sd || !attr))
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return -EINVAL;
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kobject_get_ownership(kobj, &uid, &gid);
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return sysfs_add_file_mode_ns(kobj->sd, attr, attr->mode, uid, gid, ns);
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}
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EXPORT_SYMBOL_GPL(sysfs_create_file_ns);
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int sysfs_create_files(struct kobject *kobj, const struct attribute * const *ptr)
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{
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int err = 0;
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int i;
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for (i = 0; ptr[i] && !err; i++)
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err = sysfs_create_file(kobj, ptr[i]);
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if (err)
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while (--i >= 0)
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sysfs_remove_file(kobj, ptr[i]);
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return err;
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}
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EXPORT_SYMBOL_GPL(sysfs_create_files);
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/**
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* sysfs_add_file_to_group - add an attribute file to a pre-existing group.
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* @kobj: object we're acting for.
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* @attr: attribute descriptor.
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* @group: group name.
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*/
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int sysfs_add_file_to_group(struct kobject *kobj,
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const struct attribute *attr, const char *group)
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{
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struct kernfs_node *parent;
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kuid_t uid;
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kgid_t gid;
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int error;
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if (group) {
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parent = kernfs_find_and_get(kobj->sd, group);
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} else {
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parent = kobj->sd;
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kernfs_get(parent);
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}
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if (!parent)
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return -ENOENT;
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kobject_get_ownership(kobj, &uid, &gid);
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error = sysfs_add_file_mode_ns(parent, attr, attr->mode, uid, gid,
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NULL);
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kernfs_put(parent);
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return error;
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}
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EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
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/**
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* sysfs_chmod_file - update the modified mode value on an object attribute.
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* @kobj: object we're acting for.
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* @attr: attribute descriptor.
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* @mode: file permissions.
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*
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*/
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int sysfs_chmod_file(struct kobject *kobj, const struct attribute *attr,
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umode_t mode)
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{
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struct kernfs_node *kn;
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struct iattr newattrs;
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int rc;
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kn = kernfs_find_and_get(kobj->sd, attr->name);
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if (!kn)
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return -ENOENT;
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newattrs.ia_mode = (mode & S_IALLUGO) | (kn->mode & ~S_IALLUGO);
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newattrs.ia_valid = ATTR_MODE;
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rc = kernfs_setattr(kn, &newattrs);
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kernfs_put(kn);
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return rc;
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}
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EXPORT_SYMBOL_GPL(sysfs_chmod_file);
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/**
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* sysfs_break_active_protection - break "active" protection
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* @kobj: The kernel object @attr is associated with.
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* @attr: The attribute to break the "active" protection for.
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*
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* With sysfs, just like kernfs, deletion of an attribute is postponed until
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* all active .show() and .store() callbacks have finished unless this function
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* is called. Hence this function is useful in methods that implement self
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* deletion.
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*/
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struct kernfs_node *sysfs_break_active_protection(struct kobject *kobj,
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const struct attribute *attr)
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{
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struct kernfs_node *kn;
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kobject_get(kobj);
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kn = kernfs_find_and_get(kobj->sd, attr->name);
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if (kn)
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kernfs_break_active_protection(kn);
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return kn;
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}
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EXPORT_SYMBOL_GPL(sysfs_break_active_protection);
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/**
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* sysfs_unbreak_active_protection - restore "active" protection
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* @kn: Pointer returned by sysfs_break_active_protection().
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*
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* Undo the effects of sysfs_break_active_protection(). Since this function
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* calls kernfs_put() on the kernfs node that corresponds to the 'attr'
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* argument passed to sysfs_break_active_protection() that attribute may have
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* been removed between the sysfs_break_active_protection() and
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* sysfs_unbreak_active_protection() calls, it is not safe to access @kn after
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* this function has returned.
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*/
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void sysfs_unbreak_active_protection(struct kernfs_node *kn)
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{
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struct kobject *kobj = kn->parent->priv;
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kernfs_unbreak_active_protection(kn);
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kernfs_put(kn);
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kobject_put(kobj);
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}
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EXPORT_SYMBOL_GPL(sysfs_unbreak_active_protection);
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/**
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* sysfs_remove_file_ns - remove an object attribute with a custom ns tag
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* @kobj: object we're acting for
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* @attr: attribute descriptor
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* @ns: namespace tag of the file to remove
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*
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* Hash the attribute name and namespace tag and kill the victim.
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*/
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void sysfs_remove_file_ns(struct kobject *kobj, const struct attribute *attr,
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const void *ns)
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{
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struct kernfs_node *parent = kobj->sd;
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kernfs_remove_by_name_ns(parent, attr->name, ns);
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}
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EXPORT_SYMBOL_GPL(sysfs_remove_file_ns);
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/**
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* sysfs_remove_file_self - remove an object attribute from its own method
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* @kobj: object we're acting for
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* @attr: attribute descriptor
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*
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* See kernfs_remove_self() for details.
|
|
*/
|
|
bool sysfs_remove_file_self(struct kobject *kobj, const struct attribute *attr)
|
|
{
|
|
struct kernfs_node *parent = kobj->sd;
|
|
struct kernfs_node *kn;
|
|
bool ret;
|
|
|
|
kn = kernfs_find_and_get(parent, attr->name);
|
|
if (WARN_ON_ONCE(!kn))
|
|
return false;
|
|
|
|
ret = kernfs_remove_self(kn);
|
|
|
|
kernfs_put(kn);
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(sysfs_remove_file_self);
|
|
|
|
void sysfs_remove_files(struct kobject *kobj, const struct attribute * const *ptr)
|
|
{
|
|
int i;
|
|
|
|
for (i = 0; ptr[i]; i++)
|
|
sysfs_remove_file(kobj, ptr[i]);
|
|
}
|
|
EXPORT_SYMBOL_GPL(sysfs_remove_files);
|
|
|
|
/**
|
|
* sysfs_remove_file_from_group - remove an attribute file from a group.
|
|
* @kobj: object we're acting for.
|
|
* @attr: attribute descriptor.
|
|
* @group: group name.
|
|
*/
|
|
void sysfs_remove_file_from_group(struct kobject *kobj,
|
|
const struct attribute *attr, const char *group)
|
|
{
|
|
struct kernfs_node *parent;
|
|
|
|
if (group) {
|
|
parent = kernfs_find_and_get(kobj->sd, group);
|
|
} else {
|
|
parent = kobj->sd;
|
|
kernfs_get(parent);
|
|
}
|
|
|
|
if (parent) {
|
|
kernfs_remove_by_name(parent, attr->name);
|
|
kernfs_put(parent);
|
|
}
|
|
}
|
|
EXPORT_SYMBOL_GPL(sysfs_remove_file_from_group);
|
|
|
|
/**
|
|
* sysfs_create_bin_file - create binary file for object.
|
|
* @kobj: object.
|
|
* @attr: attribute descriptor.
|
|
*/
|
|
int sysfs_create_bin_file(struct kobject *kobj,
|
|
const struct bin_attribute *attr)
|
|
{
|
|
kuid_t uid;
|
|
kgid_t gid;
|
|
|
|
if (WARN_ON(!kobj || !kobj->sd || !attr))
|
|
return -EINVAL;
|
|
|
|
kobject_get_ownership(kobj, &uid, &gid);
|
|
return sysfs_add_bin_file_mode_ns(kobj->sd, attr, attr->attr.mode, uid,
|
|
gid, NULL);
|
|
}
|
|
EXPORT_SYMBOL_GPL(sysfs_create_bin_file);
|
|
|
|
/**
|
|
* sysfs_remove_bin_file - remove binary file for object.
|
|
* @kobj: object.
|
|
* @attr: attribute descriptor.
|
|
*/
|
|
void sysfs_remove_bin_file(struct kobject *kobj,
|
|
const struct bin_attribute *attr)
|
|
{
|
|
kernfs_remove_by_name(kobj->sd, attr->attr.name);
|
|
}
|
|
EXPORT_SYMBOL_GPL(sysfs_remove_bin_file);
|
|
|
|
static int internal_change_owner(struct kernfs_node *kn, kuid_t kuid,
|
|
kgid_t kgid)
|
|
{
|
|
struct iattr newattrs = {
|
|
.ia_valid = ATTR_UID | ATTR_GID,
|
|
.ia_uid = kuid,
|
|
.ia_gid = kgid,
|
|
};
|
|
return kernfs_setattr(kn, &newattrs);
|
|
}
|
|
|
|
/**
|
|
* sysfs_link_change_owner - change owner of a sysfs file.
|
|
* @kobj: object of the kernfs_node the symlink is located in.
|
|
* @targ: object of the kernfs_node the symlink points to.
|
|
* @name: name of the link.
|
|
* @kuid: new owner's kuid
|
|
* @kgid: new owner's kgid
|
|
*
|
|
* This function looks up the sysfs symlink entry @name under @kobj and changes
|
|
* the ownership to @kuid/@kgid. The symlink is looked up in the namespace of
|
|
* @targ.
|
|
*
|
|
* Returns 0 on success or error code on failure.
|
|
*/
|
|
int sysfs_link_change_owner(struct kobject *kobj, struct kobject *targ,
|
|
const char *name, kuid_t kuid, kgid_t kgid)
|
|
{
|
|
struct kernfs_node *kn = NULL;
|
|
int error;
|
|
|
|
if (!name || !kobj->state_in_sysfs || !targ->state_in_sysfs)
|
|
return -EINVAL;
|
|
|
|
error = -ENOENT;
|
|
kn = kernfs_find_and_get_ns(kobj->sd, name, targ->sd->ns);
|
|
if (!kn)
|
|
goto out;
|
|
|
|
error = -EINVAL;
|
|
if (kernfs_type(kn) != KERNFS_LINK)
|
|
goto out;
|
|
if (kn->symlink.target_kn->priv != targ)
|
|
goto out;
|
|
|
|
error = internal_change_owner(kn, kuid, kgid);
|
|
|
|
out:
|
|
kernfs_put(kn);
|
|
return error;
|
|
}
|
|
|
|
/**
|
|
* sysfs_file_change_owner - change owner of a sysfs file.
|
|
* @kobj: object.
|
|
* @name: name of the file to change.
|
|
* @kuid: new owner's kuid
|
|
* @kgid: new owner's kgid
|
|
*
|
|
* This function looks up the sysfs entry @name under @kobj and changes the
|
|
* ownership to @kuid/@kgid.
|
|
*
|
|
* Returns 0 on success or error code on failure.
|
|
*/
|
|
int sysfs_file_change_owner(struct kobject *kobj, const char *name, kuid_t kuid,
|
|
kgid_t kgid)
|
|
{
|
|
struct kernfs_node *kn;
|
|
int error;
|
|
|
|
if (!name)
|
|
return -EINVAL;
|
|
|
|
if (!kobj->state_in_sysfs)
|
|
return -EINVAL;
|
|
|
|
kn = kernfs_find_and_get(kobj->sd, name);
|
|
if (!kn)
|
|
return -ENOENT;
|
|
|
|
error = internal_change_owner(kn, kuid, kgid);
|
|
|
|
kernfs_put(kn);
|
|
|
|
return error;
|
|
}
|
|
EXPORT_SYMBOL_GPL(sysfs_file_change_owner);
|
|
|
|
/**
|
|
* sysfs_change_owner - change owner of the given object.
|
|
* @kobj: object.
|
|
* @kuid: new owner's kuid
|
|
* @kgid: new owner's kgid
|
|
*
|
|
* Change the owner of the default directory, files, groups, and attributes of
|
|
* @kobj to @kuid/@kgid. Note that sysfs_change_owner mirrors how the sysfs
|
|
* entries for a kobject are added by driver core. In summary,
|
|
* sysfs_change_owner() takes care of the default directory entry for @kobj,
|
|
* the default attributes associated with the ktype of @kobj and the default
|
|
* attributes associated with the ktype of @kobj.
|
|
* Additional properties not added by driver core have to be changed by the
|
|
* driver or subsystem which created them. This is similar to how
|
|
* driver/subsystem specific entries are removed.
|
|
*
|
|
* Returns 0 on success or error code on failure.
|
|
*/
|
|
int sysfs_change_owner(struct kobject *kobj, kuid_t kuid, kgid_t kgid)
|
|
{
|
|
int error;
|
|
const struct kobj_type *ktype;
|
|
|
|
if (!kobj->state_in_sysfs)
|
|
return -EINVAL;
|
|
|
|
/* Change the owner of the kobject itself. */
|
|
error = internal_change_owner(kobj->sd, kuid, kgid);
|
|
if (error)
|
|
return error;
|
|
|
|
ktype = get_ktype(kobj);
|
|
if (ktype) {
|
|
/*
|
|
* Change owner of the default groups associated with the
|
|
* ktype of @kobj.
|
|
*/
|
|
error = sysfs_groups_change_owner(kobj, ktype->default_groups,
|
|
kuid, kgid);
|
|
if (error)
|
|
return error;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(sysfs_change_owner);
|
|
|
|
/**
|
|
* sysfs_emit - scnprintf equivalent, aware of PAGE_SIZE buffer.
|
|
* @buf: start of PAGE_SIZE buffer.
|
|
* @fmt: format
|
|
* @...: optional arguments to @format
|
|
*
|
|
*
|
|
* Returns number of characters written to @buf.
|
|
*/
|
|
int sysfs_emit(char *buf, const char *fmt, ...)
|
|
{
|
|
va_list args;
|
|
int len;
|
|
|
|
if (WARN(!buf || offset_in_page(buf),
|
|
"invalid sysfs_emit: buf:%p\n", buf))
|
|
return 0;
|
|
|
|
va_start(args, fmt);
|
|
len = vscnprintf(buf, PAGE_SIZE, fmt, args);
|
|
va_end(args);
|
|
|
|
return len;
|
|
}
|
|
EXPORT_SYMBOL_GPL(sysfs_emit);
|
|
|
|
/**
|
|
* sysfs_emit_at - scnprintf equivalent, aware of PAGE_SIZE buffer.
|
|
* @buf: start of PAGE_SIZE buffer.
|
|
* @at: offset in @buf to start write in bytes
|
|
* @at must be >= 0 && < PAGE_SIZE
|
|
* @fmt: format
|
|
* @...: optional arguments to @fmt
|
|
*
|
|
*
|
|
* Returns number of characters written starting at &@buf[@at].
|
|
*/
|
|
int sysfs_emit_at(char *buf, int at, const char *fmt, ...)
|
|
{
|
|
va_list args;
|
|
int len;
|
|
|
|
if (WARN(!buf || offset_in_page(buf) || at < 0 || at >= PAGE_SIZE,
|
|
"invalid sysfs_emit_at: buf:%p at:%d\n", buf, at))
|
|
return 0;
|
|
|
|
va_start(args, fmt);
|
|
len = vscnprintf(buf + at, PAGE_SIZE - at, fmt, args);
|
|
va_end(args);
|
|
|
|
return len;
|
|
}
|
|
EXPORT_SYMBOL_GPL(sysfs_emit_at);
|