From mboxrd@z Thu Jan  1 00:00:00 1970
From: greg@kroah.com (Greg KH)
Date: Thu, 6 Apr 2017 08:08:20 +0200
Subject: generic memory addresses
In-Reply-To: <20170406003101.GH18834@eros>
References: <20170406003101.GH18834@eros>
Message-ID: <20170406060820.GA9759@kroah.com>
To: kernelnewbies@lists.kernelnewbies.org
List-Id: kernelnewbies.lists.kernelnewbies.org

On Thu, Apr 06, 2017 at 10:31:01AM +1000, Tobin C. Harding wrote:
> Why is there code in-tree that declares generic memory addresses as
> unsigned int?
> 
> Linux Device Drivers 3rd Edition page 289
>  Therefore, generic memory addresses in the kernel are usually unsigned
>  long, exploiting the fact that pointers and long integers are always
>  the same size, at least on all the platforms currently supported by
>  Linux.
> 
> It would therefore seem like a bug to declare a generic memory address
> as an unsigned int in code that can run on 64 bit machines.

I agree, that does seem like a bug.

> What is the explanation for such declarations in the kernel please?
> 
> $ cd KERNEL_TREE
> $ git grep 'unsigned int addr' | wc -l
> 556

Make sure those really are being used to store a real address, sometimes
they are not...

thanks,

greg k-h