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

[Greg KH]

On Wed, Dec 02, 2020 at 01:02:06PM -0500, Andrey Grodzovsky wrote:
> 
> On 12/2/20 12:34 PM, Greg KH wrote:
> > On Wed, Dec 02, 2020 at 10:48:01AM -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%7C29ff7efb89bd47d8488708d896e86e7c%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637425272317529134%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=Vzc3fVofA6%2BMPSqHmBqcWavQLKWU1%2FXKJFun24irLf0%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.
> > > 
> > > Hi Greg, I tried your suggestion to hang amdgpu's sysfs
> > > attributes on default attributes in struct device.groups but turns out it's
> > > not usable since by the
> > > time i have access to struct device from amdgpu code it has already been
> > > initialized by pci core
> > > (i.e.  past the point where device_add->device_add_attrs->device_add_groups
> > > with dev->groups is called)
> > > and so i can't really use it.
> > That's odd, why can't you just set the groups pointer in your pci_driver
> > structure?  That's what it is there for, right?
> 
> I am probably missing something but amdgpu sysfs attrs are per device not
> per driver

Oops, you are right, you want the 'dev_groups' field.  Looks like pci
doesn't export that directly, so you can do:
	.driver {
		.dev_groups = my_device_groups;
	},
in your pci_driver structure.

Or I'm sure the PCI driver maintainer would take a patch like
7d9c1d2f7aca ("USB: add support for dev_groups to struct
usb_device_driver") was done for the USB subsystem, as diving into the
"raw" .driver pointer isn't really that clean or nice in my opinion.

thanks,

greg k-h