[alsa-devel] [PATCH, for-next] ALSA: usb-audio: caiaq: fix endianness bug in snd_usb_caiaq_maschine_dispatch

[Daniel Mack]

On 29.04.2013 21:15, Eldad Zack wrote:
> Current code does this:
> 
>   be16_to_cpu(buf[i * 2] << 8 | buf[(i * 2) + 1])
> 
> Which is effectively (neglecting the index):
> 
>   be16_to_cpu(be16_to_cpu(*((u16 *) buf)))
> 
> This means the int16 in the buffer is not converted at all.
> 
> Daniel Mack confirmed that the driver works on little endian
> CPUs, leading to the conclusion that the device-side structure
> is actually little endian.
> This changes the code to use le16_to_cpu().
> 
> Caught by sparse.
> 
> Acked-by: Daniel Mack <zonque at gmail.com>
> Signed-off-by: Eldad Zack <eldad at fogrefinery.com>

Appearantly, nobody (including me) has ever used the pad controls of
this particular device on a BE machine. So I think it might not even be
worth Cc'ing stable.


Thanks for catching this, anyway!

Daniel



> ---
>  sound/usb/caiaq/input.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/sound/usb/caiaq/input.c b/sound/usb/caiaq/input.c
> index efc70ae..4b3fb91 100644
> --- a/sound/usb/caiaq/input.c
> +++ b/sound/usb/caiaq/input.c
> @@ -488,13 +488,13 @@ static void snd_usb_caiaq_maschine_dispatch(struct snd_usb_caiaqdev *cdev,
>  					unsigned int len)
>  {
>  	unsigned int i, pad_id;
> -	uint16_t pressure;
> +	__le16 *pressure = (__le16 *) buf;
>  
>  	for (i = 0; i < MASCHINE_PADS; i++) {
> -		pressure = be16_to_cpu(buf[i * 2] << 8 | buf[(i * 2) + 1]);
> -		pad_id = pressure >> 12;
> -
> -		input_report_abs(cdev->input_dev, MASCHINE_PAD(pad_id), pressure & 0xfff);
> +		pad_id = le16_to_cpu(*pressure) >> 12;
> +		input_report_abs(cdev->input_dev, MASCHINE_PAD(pad_id),
> +				 le16_to_cpu(*pressure) & 0xfff);
> +		pressure++;
>  	}
>  
>  	input_sync(cdev->input_dev);
>