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    SubjectRe: scripts/mod/file2alias.c cross compile problem
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    On Sat, 2007-07-28 at 03:39 +0200, Adrian Bunk wrote:
    > On Fri, Jul 27, 2007 at 04:21:47PM -0700, Luck, Tony wrote:
    > > > So it seems on ia64 with gcc 3.3.6 there's some 8 byte alignment of the
    > > > array members?
    > > >
    > > > Sam and the ia64 maintainers Cc'ed - they might know better what's going
    > > > on here.
    > >
    > > This ia64 maintainer is baffled ... but I don't see the problem here (perhaps
    > > because my build machine has gcc 3.4.6).
    >
    >
    > I found what causes this problem, and it only occurs during cross
    > compilation.
    >
    >
    > The struct is:
    >
    > #define ACPI_ID_LEN 9
    >
    > struct acpi_device_id {
    > __u8 id[ACPI_ID_LEN];
    > kernel_ulong_t driver_data;
    > };
    >
    >
    > When compiling for ia64, this results in:
    >
    > struct acpi_device_id {
    > __u8 id[9];
    > uint64_t driver_data;
    > };
    >
    >
    > sizeof(struct acpi_device_id) for ia64 is due to different padding
    > after id[] 20 bytes on i386 but 24 bytes on ia64.
    >
    > scripts/mod/file2alias.c is compiled with HOSTCC and ensures that
    > kernel_ulong_t is correct (in this case uint64_t for ia64), but it can't
    > cope with different padding on different architectures.

    This one should workaround it. Is this acceptable for now?
    Don't know how to fix this in a cleaner way (but I am sure it's
    possible... ). Maybe an IA64 guy who is more used to such things has a
    better idea and could have a look at this if there is time...

    Thomas

    -------------

    Cross-compilation between e.g. i386 -> 64bit could break -> work around it

    Adrian Bunk: scripts/mod/file2alias.c is compiled with HOSTCC and ensures that
    kernel_ulong_t is correct, but it can't cope with different padding on
    different architectures.

    ---
    include/linux/mod_devicetable.h | 2 ++
    1 file changed, 2 insertions(+)

    Index: torvalds/include/linux/mod_devicetable.h
    ===================================================================
    --- torvalds.orig/include/linux/mod_devicetable.h
    +++ torvalds/include/linux/mod_devicetable.h
    @@ -160,9 +160,11 @@ struct ap_device_id {
    #define AP_DEVICE_ID_MATCH_DEVICE_TYPE 0x01

    #define ACPI_ID_LEN 9
    +#define FILLUP_LEN 7 /* dirty fix for i386 -> 64bit cross-compilation */

    struct acpi_device_id {
    __u8 id[ACPI_ID_LEN];
    + __u8 dummy[FILLUP_LEN];
    kernel_ulong_t driver_data;
    };


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