Re: Kernel symbol version history

On Wed, 2007-12-05 at 11:17 -0500, David H. Lynch Jr. wrote:

This might be slightly OT here, but would anyone know where there
might be a reference that indicates at precisely what version a given
symbol either appeared or disappeared within the  Linux kernel ?

     As an example if a driver is supposed to work for 2.6 and 2.4 and
uses sysfs, or cdev, or alloc_chr_dev_region or ...
    How can one tell at what point that api or symbol appeared so that
the proper conditionals appear within the driver.

    The last one that bit me was I made a collection of casting changes
to address 64bit vs. 32bit targets, and found that using the C99 fixed
size types - uint32_t, ... made life much more pleasant, after putting
them I nobody else could build because uintptr_t did not appear until
2.6.24, and I still have not figured out exactly when uint32_t etc.
appeared.

I believe the standard C99 types like uint32_t have been there for ever,
basically. Maybe not in Linux 1.0, but as far back as anyone might ever
sensibly care.

That doesn't include uintptr_t though. For that we usually use 'unsigned
long'. If ever there is an architecture where 'unsigned long' isn't big
enough for a pointer, Linux is going to break :)

    I would think there ought to be some resource besides group memory
to look this up ?
    Is there a way to use git to look back through the history of a
symbol rather than a file.

pmac /pmac/git/libertas-2.6 $ git-annotate include/linux/types.h | grep uintptr_t
142956af        (   Al Viro     2007-10-29 05:11:28 +0000       40)typedef unsigned long                uintptr_t;
pmac /pmac/git/libertas-2.6 $ git-show 142956af
commit 142956af525002c5378e7d91d81a01189841a785
Author: Al Viro [off-list ref]
Date:   Mon Oct 29 05:11:28 2007 +0000

    fix abuses of ptrdiff_t
    
    Use of ptrdiff_t in places like
    
    -                       if (!access_ok(VERIFY_WRITE, u_tmp->rx_buf, u_tmp->len))
    +                       if (!access_ok(VERIFY_WRITE, (u8 __user *)
    +                                               (ptrdiff_t) u_tmp->rx_buf,
    +                                               u_tmp->len))
    
    is wrong; for one thing, it's a bad C (it's what uintptr_t is for; in general
    we are not even promised that ptrdiff_t is large enough to hold a pointer,
    just enough to hold a difference between two pointers within the same object).
    For another, it confuses the fsck out of sparse.
    
    Use unsigned long or uintptr_t instead.  There are several places misusing
    ptrdiff_t; fixed.
    
    Signed-off-by: Al Viro [off-list ref]
    Signed-off-by: Linus Torvalds [off-list ref]


-- 
dwmw2