lkml.org 
[lkml]   [2020]   [Sep]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] driver core: Remove double assignment
On Tue, Sep 29, 2020 at 02:25:33PM +0200, Greg Kroah-Hartman wrote:
> On Tue, Sep 29, 2020 at 01:58:08PM +0200, poeschel@lemonage.de wrote:
> > From: Lars Poeschel <poeschel@lemonage.de>
> >
> > This removes an assignment in device_add. It assigned the parent
> > kobject to the kobject of the new device. This is not necessary,
> > because the call to kobject_add a few lines later also does this same
> > assignment.
> >
> > Signed-off-by: Lars Poeschel <poeschel@lemonage.de>
> > ---
> > drivers/base/core.c | 4 +---
> > 1 file changed, 1 insertion(+), 3 deletions(-)
> >
> > diff --git a/drivers/base/core.c b/drivers/base/core.c
> > index bb5806a2bd4c..03b5396cd192 100644
> > --- a/drivers/base/core.c
> > +++ b/drivers/base/core.c
> > @@ -2847,8 +2847,6 @@ int device_add(struct device *dev)
> > error = PTR_ERR(kobj);
> > goto parent_error;
> > }
> > - if (kobj)
> > - dev->kobj.parent = kobj;
> >
> > /* use parent numa_node */
> > if (parent && (dev_to_node(dev) == NUMA_NO_NODE))
> > @@ -2856,7 +2854,7 @@ int device_add(struct device *dev)
> >
> > /* first, register with generic layer. */
> > /* we require the name to be set before, and pass NULL */
> > - error = kobject_add(&dev->kobj, dev->kobj.parent, NULL);
> > + error = kobject_add(&dev->kobj, kobj, NULL);
>
> That's very subtle, and might not really be correct for all users, have
> you checked?

Of course I have not checked for all users ;-), but I have checked this
for my system and I did not notice any difference. My system is an arm
based board that does several hundreds of calls to the device_add
function per kernel bootup.

> Anyway, I'd rather leave this as-is if possible, as we know this works
> correctly, and it is not going to save any time/energy to remove that
> assignment, right?

Of course it's up to you to leave this as is.
Pure binary size drops from 0x784 to 0x778 (12 bytes) with this patch
for the device_add function on arm with gcc 10.2.0.
So this saves a tiny amount of size and energy. If it's worth that, I
don't know.
And not to mention the time/energy you save when some time some random
guy again stubles upon this, sends you a patch and then you have to
reply. ;-)

Ok, as said:Taking this is up to you. I can also live without this.

Regards,
Lars

\
 
 \ /
  Last update: 2020-09-29 15:15    [W:0.027 / U:0.836 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site