On Sat, May 28, 2011 at 10:22:20PM +0200, Belisko Marek wrote:
On Sat, May 28, 2011 at 9:43 PM, Robert P. J. Day <rpjday@crashcourse.ca> wrote:
On Sat, 28 May 2011, Belisko Marek wrote:
On Sat, May 28, 2011 at 6:29 PM, Robert P. J. Day <rpjday@crashcourse.ca> wrote:
i agree that there should be a "put_device(&dev->dev);" statement as you show above. however, i still don't see how this can be just a stylistic improvement as you seem to suggest. based on the warning from the kernel source file, it would seem that you *must* do a put_device() in that situation -- it's not optional.
Sure you're right. You can send a patch to fix this problem. Good catch.
i didn't want to submit anything until i verified what correct code should look like. and it's not like that's the only example -- others are trivially easy to find, like this in drivers/media/video/bt8xx/bttv-gpio.c (line 97):
err = device_register(&sub->dev); if (0 != err) { kfree(sub); return err; } I'm little bit confused. If you look at device_add which is part of device_register if something in device_add failed it will always call put_device (in any error case) so why then is necessary to call it again when device_register return error?
Because there still is a "dangling" reference on the device. You wouldn't want the device to be "gone" without you really knowing about it, right? If the device_register fails, you might need to do something with the larger "device" structure before doing the last put_device() to clean up the memory (like unwind other things you set up before calling device_register.) Trust me, dig through the driver core and kobject model, it's tricky to follow, but it's there. Or at least it was there the last time I did this, that is why I documented it so that no one would have to do that again and they could just easily follow the rules. Hope this helps, greg k-h