Re: [PATCH v3] ALSA: compress: add support for 32bit calls in a 64bit kernel

[Vinod Koul <vinod.koul@intel.com>]

On Mon, Dec 07, 2015 at 12:08:31PM +0530, Ravindra Lokhande wrote:
> Compress offload does not support ioctl calls from a 32bit userspace
> in a 64 bit kernel. This patch adds support for ioctls from a 32bit
> userspace in a 64bit kernel
> 
> Signed-off-by: Ravindra Lokhande <rlokhande@nvidia.com>
> ---
> 
> v1 -> v2: use compat_ptr to convert 32 bit address to 64 bit pointer
> v2 -> v3: add header file compat.h
> 
>  sound/core/compress_offload.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
> index b123c42..4597820 100644
> --- a/sound/core/compress_offload.c
> +++ b/sound/core/compress_offload.c
> @@ -38,6 +38,7 @@
>  #include <linux/uio.h>
>  #include <linux/uaccess.h>
>  #include <linux/module.h>
> +#include <linux/compat.h>
>  #include <sound/core.h>
>  #include <sound/initval.h>
>  #include <sound/compress_params.h>
> @@ -847,6 +848,15 @@ static long snd_compr_ioctl(struct file *f, unsigned int cmd, unsigned long arg)
>  	return retval;
>  }
>  
> +/* support of 32bit userspace on 64bit platforms */
> +#ifdef CONFIG_COMPAT
> +static long snd_compr_ioctl_compat(struct file *file, unsigned int cmd,
> +						unsigned long arg)
> +{
> +	return snd_compr_ioctl(file, cmd, (unsigned long)compat_ptr(arg));
> +}
> +#endif
> +
>  static const struct file_operations snd_compr_file_ops = {
>  		.owner =	THIS_MODULE,
>  		.open =		snd_compr_open,
> @@ -854,6 +864,9 @@ static const struct file_operations snd_compr_file_ops = {
>  		.write =	snd_compr_write,
>  		.read =		snd_compr_read,
>  		.unlocked_ioctl = snd_compr_ioctl,
> +#ifdef CONFIG_COMPAT
> +		.compat_ioctl = snd_compr_ioctl_compat,
> +#endif

While this change is okay and required, I can't help wondering why the core
does not take care of this.

When a driver does not support compat_ioctl as it was done recently and
takes care of 32/64 bit issues we should call ioctl for that driver..

Neverthless, Acked-by Vinod Koul <vinod.koul@intel.com>

-- 
~Vinod