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

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

[Eldad Zack]

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@gmail.com>
Signed-off-by: Eldad Zack <eldad@fogrefinery.com>
---
 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);
-- 
1.8.1.5

Re: [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@gmail.com>
> Signed-off-by: Eldad Zack <eldad@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);
> 

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

[Takashi Iwai]

At Mon, 29 Apr 2013 21:20:43 +0200,
Daniel Mack wrote:
> 
> 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@gmail.com>
> > Signed-off-by: Eldad Zack <eldad@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.

OK.  Applied as is now.
Thanks.

Takashi

> 
> 
> 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);
> > 
>