linux-kernel - Re: bttv-driver.c:3964: error: void value not ignored as it ought to be

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Message-ID: <44BC4F83.6060108@linuxtv.org>
Date:	Mon, 17 Jul 2006 23:03:31 -0400
From:	Michael Krufky <mkrufky@...uxtv.org>
To:	Linux and Kernel Video <video4linux-list@...hat.com>
CC:	Andrew Morton <akpm@...l.org>, Axel Thimm <Axel.Thimm@...pms.net>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Mauro Carvalho Chehab <mchehab@...radead.org>,
	Randy Dunlap <rdunlap@...otime.net>
Subject: Re: bttv-driver.c:3964: error: void value not ignored as it ought
 to be

Michael Krufky wrote:
> Nish Aravamudan wrote:
>> On 7/17/06, Michael Krufky <mkrufky@...uxtv.org> 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 ( 
http://linuxtv.org/hg/~mkrufky/v4l-dvb ) 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)
  {
-#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,17)
-       int ret;
-#endif
-
         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->c.nr,btv->video_dev->minor & 0x1f);
-#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,17)
-       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);
-#else
  #if LINUX_VERSION_CODE > KERNEL_VERSION(2,5,0)

         video_device_create_file(btv->video_dev, &class_device_attr_card);
  #endif
-#endif

         /* 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

  #if LINUX_VERSION_CODE > KERNEL_VERSION(2,5,0)
  #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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