LinuxKPI,lindebugfs: add more base type support

[bz]

Summary

Add debugfs_create_u8() based on other already present implementations.
I am unclear if we need to add extra checks.

Add a dummy (no real implementation yet) for debugfs_create_blob().

Both are needed for iwlwifi debugfs support.

[bz]

This is just so to have the skeleton for a discussion on how to implement "blob" properly. I am hoping @jfree may have a good idea.

[bz]

Add missing struct definition already in my local file from earlier work.

[jfree]

I feel like the scattered nature of debugfs material makes it incredibly difficult to work with.
Perhaps something along the lines of this would work:

static int
debugfs_blob_get(void *data, uint64_t *value)
{
	struct debugfs_blob_wrapper *blob = data;
	memcpy(value, blob->data, blob->size);
	return (0);
}

static int
debugfs_blob_set(void *data, uint64_t value)
{
	struct debugfs_blob_wrapper *blob = data;
	blob->size = sizeof(value);
	memcpy(blob->data, &value, blob->size);
	return (0);
}

I think the blob's fops should be defined manually rather than using DEFINE_DEBUGFS_ATTRIBUTE.
This will allow us to malloc the blob->data member in an open fop and free data in the release fop.
The problem is, this malloc would only account for a single sized blob. We would need to add bounds
checking in the blob's get and set functions to ensure safety.

Alternatively, we could dynamically malloc in debugfs_blob_set, but I do not know how to reliably free that.

I am not sure what the origin authors intended for the implementation. Let me know what you think.

[bz]

Implement ro blob support.

[jfree]

I just took a quick glance, but everything looks good :)
Take a look at my inline comment, though.

sys/compat/lindebugfs/lindebugfs.c

460–462

You can probably use debugfs_create_file() instead of debugfs_create_mode_unsafe() since both of your fops are RO.

[bz]

Use debugfs_create_file() to create blobs as suggested by @jfree

[bz]

Anyone care to further review / accept this?