linux-kernel - Re: [PATCH 6/7] char/mei: Header file contain the Userland API, (IOCTL and its struct)

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Message-Id: <201103221741.18141.arnd@arndb.de>
Date:	Tue, 22 Mar 2011 17:41:17 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Greg KH <gregkh@...e.de>
Cc:	Oren Weil <oren.jer.weil@...el.com>, linux-kernel@...r.kernel.org,
	alan@...ux.intel.com, david@...dhou.se
Subject: Re: [PATCH 6/7] char/mei: Header file contain the Userland API, (IOCTL and its struct)

On Tuesday 22 March 2011, Greg KH wrote:
> On Tue, Mar 22, 2011 at 12:51:31PM +0200, Oren Weil wrote:
> > +/*
> > + * Intel MEI client information struct
> > + */
> > +struct mei_client {
> > +     u32 max_msg_length;
> > +     u8 protocol_version;
> > +     u8 reserved[3];
> > +} __packed;
> 
> As this is passing the kernel/user boundry, you need to use the proper
> data types for it.
> 
> So use __u32 and __u8 here please.

Also, __packed should not be used in APIs, because it is a gcc extension
and makes the code less efficient.

> > +/*
> > + * IOCTL Connect Client Data structure
> > + */
> > +struct mei_connect_client_data {
> > +     union {
> > +             uuid_le in_client_uuid;
> > +             struct mei_client out_client_propeties;
> > +     } d;
> 
> Why not an anonymous union?

That would also incompatible with some compilers. I would recommend
not using a union at all, but simply to put all in one struct.

	Arnd
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