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    DateSat, 23 Feb 2008 12:45:38 -0800 (PST)
    FromLinus Torvalds <>
    SubjectRe: [PATCH] Use userland-like functions for reading the ACPI table
    
    On Sat, 23 Feb 2008, Éric Piel wrote:
    > 
    > As recommended by Christoph Hellwig, even if we can't rely on the userspace
    > firmware loader so early at boot, at least use normal syscall (as in
    > init/do_mounts_*.c). Similarly, use kfree() instead of ACPI_FREE().
    
    So I'm missing a lot of the background here.
    
    I don't think "sys_open()" is in any way preferable to the alternatives, 
    especially since it depends on thread-global state (the file descriptor 
    table) rather than much more local state ("struct file" that you've 
    opened).
    
    I think the calls to sys_open() in init do_dounts etc are very different: 
    they really are more about a real kernel-level almost-user-mode thread 
    than a core driver. 
    
    I *also* think this patch is just fundamentally broken regardless. You 
    can't just cast a kernel pointer to (char __user *). The two can be in 
    totally different address spaces. There's a reason why it used to do that 
    whole dance with oldfs.
    
    [ Of course, on platforms where ACPI actually runs this is not the case, 
      but that is not an excuse for doing things wrong ]
    
    So I would NAK this patch - it looks buggy, and the reason for it is not 
    sufficiently explained in the first place.
    
    		Linus
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