[PATCH] vfio-mdev: fix non-standard ioctl return val causing i386 build fail

[PATCH] vfio-mdev: fix non-standard ioctl return val causing i386 build fail

[Paul Gortmaker]

What appears to be a copy and paste error from the line above gets
the ioctl a ssize_t return value instead of the traditional "int".

The associated sample code used "long" which meant it would compile
for x86-64 but not i386, with the latter failing as follows:

  CC [M]  samples/vfio-mdev/mtty.o
samples/vfio-mdev/mtty.c:1418:20: error: initialization from incompatible pointer type [-Werror=incompatible-pointer-types]
  .ioctl          = mtty_ioctl,
                    ^
samples/vfio-mdev/mtty.c:1418:20: note: (near initialization for ‘mdev_fops.ioctl’)
cc1: some warnings being treated as errors

Use the standard "int" ioctl return value in both the header and
the sample code to fix the issue.

Fixes: 9d1a546c53b4 ("docs: Sample driver to demonstrate how to use Mediated device framework.")
Cc: Kirti Wankhede <kwankhede@nvidia.com>
Cc: Neo Jia <cjia@nvidia.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: kvm@vger.kernel.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
 include/linux/mdev.h     | 2 +-
 samples/vfio-mdev/mtty.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/mdev.h b/include/linux/mdev.h
index 3ee44b8d2bb3..46659572ab00 100644
--- a/include/linux/mdev.h
+++ b/include/linux/mdev.h
@@ -78,7 +78,7 @@ struct mdev_parent_ops {
 			size_t count, loff_t *ppos);
 	ssize_t (*write)(struct mdev_device *mdev, const char __user *buf,
 			 size_t count, loff_t *ppos);
-	ssize_t (*ioctl)(struct mdev_device *mdev, unsigned int cmd,
+	int	(*ioctl)(struct mdev_device *mdev, unsigned int cmd,
 			 unsigned long arg);
 	int	(*mmap)(struct mdev_device *mdev, struct vm_area_struct *vma);
 };
diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
index 919c10d5b12e..6f0713b1f717 100644
--- a/samples/vfio-mdev/mtty.c
+++ b/samples/vfio-mdev/mtty.c
@@ -1147,7 +1147,7 @@ int mtty_get_device_info(struct mdev_device *mdev,
 	return 0;
 }
 
-static long mtty_ioctl(struct mdev_device *mdev, unsigned int cmd,
+static int mtty_ioctl(struct mdev_device *mdev, unsigned int cmd,
 			unsigned long arg)
 {
 	int ret = 0;
-- 
2.11.0

Re: [PATCH] vfio-mdev: fix non-standard ioctl return val causing i386 build fail

[Kirti Wankhede]

Thanks Paul for catching this.

In that case we should go with 'long' since mdev_parent_ops->ioctl() is
called from vfio_device_ops->ioctl() for which the return type is 'long'.

Thanks,
Kirti

On 1/4/2017 1:06 AM, Paul Gortmaker wrote:
> What appears to be a copy and paste error from the line above gets
> the ioctl a ssize_t return value instead of the traditional "int".
> 
> The associated sample code used "long" which meant it would compile
> for x86-64 but not i386, with the latter failing as follows:
> 
>   CC [M]  samples/vfio-mdev/mtty.o
> samples/vfio-mdev/mtty.c:1418:20: error: initialization from incompatible pointer type [-Werror=incompatible-pointer-types]
>   .ioctl          = mtty_ioctl,
>                     ^
> samples/vfio-mdev/mtty.c:1418:20: note: (near initialization for ‘mdev_fops.ioctl’)
> cc1: some warnings being treated as errors
> 
> Use the standard "int" ioctl return value in both the header and
> the sample code to fix the issue.
> 
> Fixes: 9d1a546c53b4 ("docs: Sample driver to demonstrate how to use Mediated device framework.")
> Cc: Kirti Wankhede <kwankhede@nvidia.com>
> Cc: Neo Jia <cjia@nvidia.com>
> Cc: Alex Williamson <alex.williamson@redhat.com>
> Cc: kvm@vger.kernel.org
> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
> ---
>  include/linux/mdev.h     | 2 +-
>  samples/vfio-mdev/mtty.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
> index 3ee44b8d2bb3..46659572ab00 100644
> --- a/include/linux/mdev.h
> +++ b/include/linux/mdev.h
> @@ -78,7 +78,7 @@ struct mdev_parent_ops {
>  			size_t count, loff_t *ppos);
>  	ssize_t (*write)(struct mdev_device *mdev, const char __user *buf,
>  			 size_t count, loff_t *ppos);
> -	ssize_t (*ioctl)(struct mdev_device *mdev, unsigned int cmd,
> +	int	(*ioctl)(struct mdev_device *mdev, unsigned int cmd,
>  			 unsigned long arg);
>  	int	(*mmap)(struct mdev_device *mdev, struct vm_area_struct *vma);
>  };
> diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
> index 919c10d5b12e..6f0713b1f717 100644
> --- a/samples/vfio-mdev/mtty.c
> +++ b/samples/vfio-mdev/mtty.c
> @@ -1147,7 +1147,7 @@ int mtty_get_device_info(struct mdev_device *mdev,
>  	return 0;
>  }
>  
> -static long mtty_ioctl(struct mdev_device *mdev, unsigned int cmd,
> +static int mtty_ioctl(struct mdev_device *mdev, unsigned int cmd,
>  			unsigned long arg)
>  {
>  	int ret = 0;
> 

Re: [PATCH] vfio-mdev: fix non-standard ioctl return val causing i386 build fail

[Alex Williamson]

On Wed, 4 Jan 2017 18:06:57 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:

> Thanks Paul for catching this.
> 
> In that case we should go with 'long' since mdev_parent_ops->ioctl() is
> called from vfio_device_ops->ioctl() for which the return type is 'long'.

Agreed, we're mirroring the struct file_operations definition of ioctl,
so the return should be a long.  Thanks,

Alex

> On 1/4/2017 1:06 AM, Paul Gortmaker wrote:
> > What appears to be a copy and paste error from the line above gets
> > the ioctl a ssize_t return value instead of the traditional "int".
> > 
> > The associated sample code used "long" which meant it would compile
> > for x86-64 but not i386, with the latter failing as follows:
> > 
> >   CC [M]  samples/vfio-mdev/mtty.o
> > samples/vfio-mdev/mtty.c:1418:20: error: initialization from incompatible pointer type [-Werror=incompatible-pointer-types]
> >   .ioctl          = mtty_ioctl,
> >                     ^
> > samples/vfio-mdev/mtty.c:1418:20: note: (near initialization for ‘mdev_fops.ioctl’)
> > cc1: some warnings being treated as errors
> > 
> > Use the standard "int" ioctl return value in both the header and
> > the sample code to fix the issue.
> > 
> > Fixes: 9d1a546c53b4 ("docs: Sample driver to demonstrate how to use Mediated device framework.")
> > Cc: Kirti Wankhede <kwankhede@nvidia.com>
> > Cc: Neo Jia <cjia@nvidia.com>
> > Cc: Alex Williamson <alex.williamson@redhat.com>
> > Cc: kvm@vger.kernel.org
> > Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
> > ---
> >  include/linux/mdev.h     | 2 +-
> >  samples/vfio-mdev/mtty.c | 2 +-
> >  2 files changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/include/linux/mdev.h b/include/linux/mdev.h
> > index 3ee44b8d2bb3..46659572ab00 100644
> > --- a/include/linux/mdev.h
> > +++ b/include/linux/mdev.h
> > @@ -78,7 +78,7 @@ struct mdev_parent_ops {
> >  			size_t count, loff_t *ppos);
> >  	ssize_t (*write)(struct mdev_device *mdev, const char __user *buf,
> >  			 size_t count, loff_t *ppos);
> > -	ssize_t (*ioctl)(struct mdev_device *mdev, unsigned int cmd,
> > +	int	(*ioctl)(struct mdev_device *mdev, unsigned int cmd,
> >  			 unsigned long arg);
> >  	int	(*mmap)(struct mdev_device *mdev, struct vm_area_struct *vma);
> >  };
> > diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
> > index 919c10d5b12e..6f0713b1f717 100644
> > --- a/samples/vfio-mdev/mtty.c
> > +++ b/samples/vfio-mdev/mtty.c
> > @@ -1147,7 +1147,7 @@ int mtty_get_device_info(struct mdev_device *mdev,
> >  	return 0;
> >  }
> >  
> > -static long mtty_ioctl(struct mdev_device *mdev, unsigned int cmd,
> > +static int mtty_ioctl(struct mdev_device *mdev, unsigned int cmd,
> >  			unsigned long arg)
> >  {
> >  	int ret = 0;
> >   

[PATCH v2] vfio-mdev: fix non-standard ioctl return val causing i386 build fail

[Paul Gortmaker]

What appears to be a copy and paste error from the line above gets
the ioctl a ssize_t return value instead of the traditional "int".

The associated sample code used "long" which meant it would compile
for x86-64 but not i386, with the latter failing as follows:

  CC [M]  samples/vfio-mdev/mtty.o
samples/vfio-mdev/mtty.c:1418:20: error: initialization from incompatible pointer type [-Werror=incompatible-pointer-types]
  .ioctl          = mtty_ioctl,
                    ^
samples/vfio-mdev/mtty.c:1418:20: note: (near initialization for ‘mdev_fops.ioctl’)
cc1: some warnings being treated as errors

Since in this case, vfio is working with struct file_operations; as such:

    long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
    long (*compat_ioctl) (struct file *, unsigned int, unsigned long);

...and so here we just standardize on long vs. the normal int that user
space typically sees and documents as per "man ioctl" and similar.

Fixes: 9d1a546c53b4 ("docs: Sample driver to demonstrate how to use Mediated device framework.")
Cc: Kirti Wankhede <kwankhede@nvidia.com>
Cc: Neo Jia <cjia@nvidia.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: kvm@vger.kernel.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---

[v1 --> v2:  promote ioctl return from int to long to align with the
 struct file_operations as per requests in review comments. ]

 include/linux/mdev.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/mdev.h b/include/linux/mdev.h
index 3ee44b8d2bb3..b6e048e1045f 100644
--- a/include/linux/mdev.h
+++ b/include/linux/mdev.h
@@ -78,7 +78,7 @@ struct mdev_parent_ops {
 			size_t count, loff_t *ppos);
 	ssize_t (*write)(struct mdev_device *mdev, const char __user *buf,
 			 size_t count, loff_t *ppos);
-	ssize_t (*ioctl)(struct mdev_device *mdev, unsigned int cmd,
+	long	(*ioctl)(struct mdev_device *mdev, unsigned int cmd,
 			 unsigned long arg);
 	int	(*mmap)(struct mdev_device *mdev, struct vm_area_struct *vma);
 };
-- 
2.11.0