[PATCH v2 5/8] drm/amdgpu: Refactor sysfs removal

[Greg KH]

On Wed, Nov 11, 2020 at 10:45:53AM -0500, Andrey Grodzovsky wrote:
> 
> On 11/11/20 10:34 AM, Greg KH wrote:
> > On Wed, Nov 11, 2020 at 10:13:13AM -0500, Andrey Grodzovsky wrote:
> > > On 11/10/20 12:59 PM, Greg KH wrote:
> > > > On Tue, Nov 10, 2020 at 12:54:21PM -0500, Andrey Grodzovsky wrote:
> > > > > Hi, back to this after a long context switch for some higher priority stuff.
> > > > > 
> > > > > So here I was able eventually to drop all this code and this change here https://nam11.safelinks.protection.outlook.com/?url=https:%2F%2Fcgit.freedesktop.org%2F~agrodzov%2Flinux%2Fcommit%2F%3Fh%3Damd-staging-drm-next-device-unplug%26id%3D61852c8a59b4dd89d637693552c73175b9f2ccd6&data=04%7C01%7CAndrey.Grodzovsky%40amd.com%7C9fbfecac94a340dfb68408d886571609%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637407055896651058%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=Ye8HJR1vidppcOBnlOgVu5GwKD2%2Bb5ztHbiI%2BubKKT0%3D&reserved=0
> > > > > was enough for me. Seems like while device_remove_file can handle the use
> > > > > case where the file and the parent directory already gone,
> > > > > sysfs_remove_group goes down in flames in that case
> > > > > due to kobj->sd being unset on device removal.
> > > > A driver shouldn't ever have to remove individual sysfs groups, the
> > > > driver core/bus logic should do it for them automatically.
> > > > 
> > > > And whenever a driver calls a sysfs_* call, that's a hint that something
> > > > is not working properly.
> > > 
> > > 
> > > Do you mean that while the driver creates the groups and files explicitly
> > > from it's different subsystems it should not explicitly remove each
> > > one of them because all of them should be removed at once (and
> > > recursively) when the device is being removed ?
> > Individual drivers should never add groups/files in sysfs, the driver
> > core should do it properly for you if you have everything set up
> > properly.  And yes, the driver core will automatically remove them as
> > well.
> > 
> > Please use the default groups attribute for your bus/subsystem and this
> > will happen automagically.
> 
> Googling for default groups attributes i found this - https://www.linuxfoundation.org/blog/2013/06/how-to-create-a-sysfs-file-correctly/

Odd, mirror of the original article:
	http://kroah.com/log/blog/2013/06/26/how-to-create-a-sysfs-file-correctly/

> Would this be what you suggest for us ? Specifically for our case the struct
> device's  groups  seems the right solution as different devices
> might have slightly diffreent sysfs attributes.

That's what the is_visable() callback in your attribute group is for, to
tell the kernel if an individual sysfs attribute should be created or
not.

thanks,

greg k-h