Re: bttv-driver.c:3964: error: void value not ignored as it oughtto be

From: Michael Krufky
Date: Mon Jul 17 2006 - 23:02:51 EST

Michael Krufky wrote:
Nish Aravamudan wrote:
On 7/17/06, Michael Krufky <mkrufky@xxxxxxxxxxx> wrote:
Hmmm... This was caused by the "Check all __must_check warnings in
bttv." patch from Randy Dunlap (cc's from original thread added)

I am aware that this was done for various reasons of sanity checking,
however, we cannot check the return value of a void ;-)
For the sanity checking, I don't think video_device_create_file()
should be a void function. It probably should return
class_device_create_file()'s return value, no? As it can fail...

You are correct... I was merely pointing out the error, but now I see it
runs deeper than I had thought. I will fix both
video_device_create_file and video_device_remove_file to return the
class_device_foo return values, then I'll push it over to Mauro.

I was in a rush when I wrote that, and I wasn't thinking. video_device_remove_file stays as a void.

Anyway, here is the fix. This is already in my tree ( ) but split into separate patches.

no s-o-b needed for now -- this will come up through Mauro.

diff -upr master/linux/drivers/media/video/bt8xx/bttv-driver.c v4l-dvb/linux/drivers/media/video/bt8xx/bttv-driver.c
--- master/linux/drivers/media/video/bt8xx/bttv-driver.c 2006-07-17 22:57:05.000000000 -0400
+++ v4l-dvb/linux/drivers/media/video/bt8xx/bttv-driver.c 2006-07-17 21:55:54.000000000 -0400
@@ -3942,10 +3942,6 @@ static void bttv_unregister_video(struct
/* register video4linux devices */
static int __devinit bttv_register_video(struct bttv *btv)
- int ret;
if (no_overlay <= 0) {
bttv_video_template.type |= VID_TYPE_OVERLAY;
} else {
@@ -3960,17 +3956,10 @@ static int __devinit bttv_register_video
goto err;
printk(KERN_INFO "bttv%d: registered device video%d\n",
btv->,btv->video_dev->minor & 0x1f);
- ret = video_device_create_file(btv->video_dev, &class_device_attr_card);
- if (ret < 0)
- printk(KERN_WARNING "bttv: video_device_create_file error: "
- "%d\n", ret);

video_device_create_file(btv->video_dev, &class_device_attr_card);

/* vbi */
btv->vbi_dev = vdev_init(btv, &bttv_vbi_template, "vbi");
diff -upr master/linux/include/media/v4l2-dev.h v4l-dvb/linux/include/media/v4l2-dev.h
--- master/linux/include/media/v4l2-dev.h 2006-07-17 22:57:06.000000000 -0400
+++ v4l-dvb/linux/include/media/v4l2-dev.h 2006-07-17 22:34:32.000000000 -0400
@@ -376,11 +376,14 @@ extern struct video_device* video_devdat

#define to_video_device(cd) container_of(cd, struct video_device, class_dev)
-static inline void
+static inline int
video_device_create_file(struct video_device *vfd,
struct class_device_attribute *attr)
- class_device_create_file(&vfd->class_dev, attr);
+ int ret = class_device_create_file(&vfd->class_dev, attr);
+ if (ret < 0)
+ printk(KERN_WARNING "%s error: %d\n", __FUNCTION__, ret);
+ return ret;
static inline void
video_device_remove_file(struct video_device *vfd,

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