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-rw-r--r--fs/sysfs/file.c65
1 files changed, 65 insertions, 0 deletions
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index b36473f..9ba492a 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -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,
};
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