Re: [Xen-devel] [PATCH RFC 09/23] lz4: add support for OSes that don't have asm/unaligned.h

[Roger Pau Monnà <roger.pau@xxxxxxxxxx>]

On 24/04/14 10:28, Ian Campbell wrote:
> On Wed, 2014-04-23 at 18:18 +0200, Roger Pau Monnà wrote:
> 
>>> In the scaffolding and not by modifying the imported code I pressume? In
>>> which case, good thanks!
>>
>> While working around this issue, I've noticed that xen/common/lz4/defs.h
>> has one branch for little endian and another one for big endian, but
>> while compiling libxc, "__LITTLE_ENDIAN" is not defined and we fall into
>> big endian, which seems wrong, because we don't have support for any big
>> endian arch.
>>
>> Would it be OK to get rid of the big endian case, and only support
>> little endian by default?
> 
> I think it would be better to #define __LITTLE_ENDIAN than to diverge
> from the upstream of this file.

We have already diverged from upstream by adding those __LITTLE_ENDIAN 
checks, the upstream file doesn't seem to contain them in any of the 
versions:

http://lxr.free-electrons.com/source/lib/lz4/lz4defs.h

The following patch removes this cruft, but I'm unsure if we want to 
keep this endianness differentiation:

diff --git a/tools/libxc/xc_dom_decompress_lz4.c 
b/tools/libxc/xc_dom_decompress_lz4.c
index 08272fe..490ec56 100644
--- a/tools/libxc/xc_dom_decompress_lz4.c
+++ b/tools/libxc/xc_dom_decompress_lz4.c
@@ -1,7 +1,6 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <inttypes.h>
-#include <endian.h>
 #include <stdint.h>
 
 #include "xg_private.h"
diff --git a/xen/common/lz4/defs.h b/xen/common/lz4/defs.h
index f46df08..d886a4e 100644
--- a/xen/common/lz4/defs.h
+++ b/xen/common/lz4/defs.h
@@ -12,7 +12,6 @@
 #include <asm/byteorder.h>
 #endif
 
-#ifdef __LITTLE_ENDIAN
 static inline u16 INIT get_unaligned_le16(const void *p)
 {
        return le16_to_cpup(p);
@@ -22,19 +21,6 @@ static inline u32 INIT get_unaligned_le32(const void *p)
 {
        return le32_to_cpup(p);
 }
-#else
-#include <asm/unaligned.h>
-
-static inline u16 INIT get_unaligned_le16(const void *p)
-{
-       return le16_to_cpu(__get_unaligned(p, 2));
-}
-
-static inline u32 INIT get_unaligned_le32(void *p)
-{
-       return le32_to_cpu(__get_unaligned(p, 4));
-}
-#endif
 
 /*
  * Detects 64 bits mode


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