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sysfs: add sysfs_bin_read()

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sysfs bin file handling will be merged into the regular file support.
This patch prepares the read path.

Copy fs/sysfs/bin.c::read() to fs/sysfs/file.c and make it use
sysfs_open_file instead of bin_buffer.  The function is identical copy
except for the use of sysfs_open_file.

The new function is added to sysfs_bin_operations.  This isn't used
yet but will eventually replace fs/sysfs/bin.c.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Tejun Heo 2013-10-01 17:42:06 -04:00 committed by Greg Kroah-Hartman
parent f9b9a6217c
commit 2f0c6b7593
1 changed files with 65 additions and 0 deletions
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65
fs/sysfs/file.c
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@ -139,6 +139,70 @@ static int sysfs_seq_show(struct seq_file *sf, void *v)
return 0;
}
/*
* Read method for bin files. As reading a bin file can have side-effects,
* the exact offset and bytes specified in read(2) call should be passed to
* the read callback making it difficult to use seq_file. Implement
* simplistic custom buffering for bin files.
*/
static ssize_t sysfs_bin_read(struct file *file, char __user *userbuf,
size_t bytes, loff_t *off)
{
struct sysfs_open_file *of = sysfs_of(file);
struct bin_attribute *battr = of->sd->s_bin_attr.bin_attr;
struct kobject *kobj = of->sd->s_parent->s_dir.kobj;
int size = file_inode(file)->i_size;
int count = min_t(size_t, bytes, PAGE_SIZE);
loff_t offs = *off;
char *buf;
if (!bytes)
return 0;
if (size) {
if (offs > size)
return 0;
if (offs + count > size)
count = size - offs;
}
buf = kmalloc(count, GFP_KERNEL);
if (!buf)
return -ENOMEM;
/* need of->sd for battr, its parent for kobj */
mutex_lock(&of->mutex);
if (!sysfs_get_active(of->sd)) {
count = -ENODEV;
mutex_unlock(&of->mutex);
goto out_free;
}
if (battr->read)
count = battr->read(file, kobj, battr, buf, offs, count);
else
count = -EIO;
sysfs_put_active(of->sd);
mutex_unlock(&of->mutex);
if (count < 0)
goto out_free;
if (copy_to_user(userbuf, buf, count)) {
count = -EFAULT;
goto out_free;
}
pr_debug("offs = %lld, *off = %lld, count = %d\n", offs, *off, count);
*off = offs + count;
out_free:
kfree(buf);
return count;
}
/**
* flush_write_buffer - push buffer to kobject
* @of: open file
@ -495,6 +559,7 @@ const struct file_operations sysfs_file_operations = {
};
const struct file_operations sysfs_bin_operations = {
.read = sysfs_bin_read,
.write = sysfs_write_file,
.llseek = generic_file_llseek,
};