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

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Date:   Tue, 3 Jan 2017 14:36:43 -0500
From:   Paul Gortmaker <paul.gortmaker@...driver.com>
To:     <linux-kernel@...r.kernel.org>
CC:     Paul Gortmaker <paul.gortmaker@...driver.com>,
        Kirti Wankhede <kwankhede@...dia.com>,
        Neo Jia <cjia@...dia.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        <kvm@...r.kernel.org>
Subject: [PATCH] vfio-mdev: fix non-standard ioctl return val causing i386 build fail

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@...dia.com>
Cc: Neo Jia <cjia@...dia.com>
Cc: Alex Williamson <alex.williamson@...hat.com>
Cc: kvm@...r.kernel.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.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