Endianess problems in linuxppc kernel

Paul Mackerras paulus at cs.anu.edu.au
Wed Apr 28 22:21:32 EST 1999

Christian Bauer <Christian.Bauer at uni-mainz.de> wrote:

> The "le16_to_cpus(&hdr->count)" fixes a real bug in the driver (it wouldn't
> work on big-endian machines, no matter how outsl/insl works), but everything
> else looks like the outsl/insl functions work with the wrong byte order
> (little-endian vs. big-endian).

Well, the driver is using insl/outsl to transfer a buffer of bytes,
not a buffer of longwords, whereas in[s]l/out[s]l are defined to
transfer longwords (32 bits), and byte-swapping is the right thing to
do when you're transferring longwords.  The driver is using insl/outsl
in order to transfer the bytes in 4 byte chunks; what it really should
use is an insl_ns/outsl_ns which doesn't do byteswapping.

> Playing a module with "mikmod" results in rhythmic noise (16 bit) or silence
> (8 bit). When I change every instance of
>   out_le32(&awacs->byteswap, sound.hard.format != AFMT_S16_BE);
> to
>   out_le32(&awacs->byteswap, sound.hard.format == AFMT_S16_BE);
> in "drivers/sound/dmasound.c", both 8 and 16 bit output work fine.

Is the application perhaps using AFMT_S16_NE (native endianness) but
assuming that that means little-endian?


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