From mboxrd@z Thu Jan  1 00:00:00 1970
From: john.chludzinski@vivaldi.net (John Chludzinski)
Date: Fri, 15 Apr 2016 08:37:56 -0400
Subject: single, comprehensive kernel data types document?
In-Reply-To: <20160415122724.GA7389@kroah.com>
References: <alpine.LFD.2.20.1604150801170.6570@localhost.localdomain>
	<20160415122724.GA7389@kroah.com>
Message-ID: <3e0913de8af67a2489ffa472ea0186f0@mail.vivaldi.net>
To: kernelnewbies@lists.kernelnewbies.org
List-Id: kernelnewbies.lists.kernelnewbies.org

Never use stdint.h? Wasn't that the intent of stdint.h ... for kernel 
code? For embedded code?

---John

On 2016-04-15 08:27, Greg KH wrote:
> On Fri, Apr 15, 2016 at 08:04:53AM -0400, Robert P. J. Day wrote:
>> 
>>   is there a single, decent online doc that explains the proper data
>> types (int16_t, int32_t and so on) to use in kernel code?
> 
> First off, never use int16_t and friends, that's not ok :)
> 
> Second, it's simple, use:
> 	u8
> 	u16
> 	u32
> 	u64
> and friends in kernel code (s8, s16, and so on for signed values.)
> 
> 'int' is a return type, and for loops and other things that you know
> will fit in that size.
> 
>> including the relationship with types to be used in code to be
>> exported to user space (include/uapi/linux/types.h)?
> 
> For values that cross the user/kernel boundry, add '__' to the front of
> the variable:
> 	__u8
> 	__u16
> 	__u32
> and so on.  NEVER use 'int' or 'long' crossing that boundry, it's not
> going to work properly.
> 
> I think one of the chapters in LDD3 describes all of this, you might
> want to re-read it for the details.
> 
> hope this helps,
> 
> greg k-h
> 
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