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    SubjectRe: [PATCH] carl9170: fix struct alignment conflict
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    On 04/02/2021 17:29, Arnd Bergmann wrote:
    > From: Arnd Bergmann <arnd@arndb.de>
    >
    > Multiple structures in the carl9170 driver have alignment
    > impossible alignment constraints that gcc warns about when
    > building with 'make W=1':
    >
    > drivers/net/wireless/ath/carl9170/fwcmd.h:243:2: warning: alignment 1 of 'union <anonymous>' is less than 4 [-Wpacked-not-aligned]
    > drivers/net/wireless/ath/carl9170/wlan.h:373:1: warning: alignment 1 of 'struct ar9170_rx_frame_single' is less than 2 [-Wpacked-not-aligned]
    >
    > In the carl9170_cmd structure, multiple members that have an explicit
    > alignment requirement of four bytes are added into a union with explicit
    > byte alignment, but this in turn is part of a structure that also has
    > four-byte alignment.
    >
    > In the wlan.h header, multiple structures contain a ieee80211_hdr member
    > that is required to be two-byte aligned to avoid alignmnet faults when
    > processing network headers, but all members are forced to be byte-aligned
    > using the __packed tag at the end of the struct definition.
    >
    > In both cases, leaving out the packing does not change the internal
    > layout of the structure but changes the alignment constraint of the
    > structure itself.
    >
    > Change all affected structures to only apply packing where it does
    > not violate the alignment requirement of the contained structure.
    >
    > Signed-off-by: Arnd Bergmann <arnd@arndb.de>

    Acked-by: Christian Lamparter <chunkeey@gmail.com>

    I've also applied this patch and a previous one dealing with VLAs to the firmware
    source at <https://github.com/chunkeey/carl9170fw>. I did a quick rebuilt and
    the same binary firmware was produced, so I think what's left is to update those
    shared firmware/driver headers some day...

    Cheers,
    Christian

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