linux-kernel - Re: [PATCH] auxiliary: Automatically generate id

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Message-ID: <20250729100132.GH402218@unreal>
Date: Tue, 29 Jul 2025 13:01:32 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Danilo Krummrich <dakr@...nel.org>
Cc: Sean Anderson <sean.anderson@...ux.dev>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ira Weiny <ira.weiny@...el.com>, linux-kernel@...r.kernel.org,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Dave Ertman <david.m.ertman@...el.com>
Subject: Re: [PATCH] auxiliary: Automatically generate id

On Tue, Jul 29, 2025 at 11:36:27AM +0200, Danilo Krummrich wrote:
> On Mon Jul 28, 2025 at 11:10 PM CEST, Sean Anderson wrote:
> > As it turns out, ids are not allowed to have semantic meaning. Their
> > only purpose is to prevent sysfs collisions. To simplify things, just
> > generate a unique id for each auxiliary device. Remove all references to
> > filling in the id member of the device.
> >
> > Signed-off-by: Sean Anderson <sean.anderson@...ux.dev>
> > ---
> >
> >  drivers/base/auxiliary.c      | 32 +++++++++++++++++++++++---------
> >  include/linux/auxiliary_bus.h | 26 ++++++++------------------
> >  2 files changed, 31 insertions(+), 27 deletions(-)
> >
> > diff --git a/drivers/base/auxiliary.c b/drivers/base/auxiliary.c
> > index dba7c8e13a53..f66067df03ad 100644
> > --- a/drivers/base/auxiliary.c
> > +++ b/drivers/base/auxiliary.c
> > @@ -264,6 +264,8 @@ static const struct bus_type auxiliary_bus_type = {
> >  	.pm = &auxiliary_dev_pm_ops,
> >  };
> >  
> > +static DEFINE_IDA(auxiliary_id);
> 
> I think this is the correct thing to do, even though the per device IDA drivers
> typically went for so far produces IDs that are easier to handle when debugging
> things.
> 
> > +
> >  /**
> >   * auxiliary_device_init - check auxiliary_device and initialize
> >   * @auxdev: auxiliary device struct
> > @@ -331,20 +333,37 @@ int __auxiliary_device_add(struct auxiliary_device *auxdev, const char *modname)
> >  		return -EINVAL;
> >  	}
> >  
> > +	ret = ida_alloc(&auxiliary_id, GFP_KERNEL);
> > +	if (ret < 0) {
> > +		dev_err(dev, "auxiliary device id_alloc fauiled: %d\n", ret);
> > +		return ret;
> > +	}
> > +	auxdev->id = ret;
> 
> This overwrites the ID number set by various drivers that (still) use the
> auxiliary_device_init() and auxiliary_device_add() pair.
> 
> While I agree with the general intent, I think it's a very bad idea to just
> perform this change silently leaving drivers with their IDA instances not
> knowing that the set ID numbers do not have an effect anymore.
> 
> I think this should be multiple steps:
> 
>   (1) Remove the id parameter and force an internal ID only for
>       auxiliary_device_create().
> 
>   (2) Convert applicable drivers (and the Rust abstraction) to use
>       auxiliary_device_create() rather than auxiliary_device_init() and
>       auxiliary_device_add().
> 
>   (3) Treewide change to force an internal ID for all auxiliary devices
>       considering this change in all affected drivers.

I would suggest easier approach.
1. Add to the proposal patch, the sed generated line which removes auxdev->id
assignment in the drivers.
Something like this from mlx5:
 - sf_dev->adev.id = id;

2. Add standalone patches to remove not used ida_alloc/ida_free calls
from the drivers.

> 
> > +
> >  	ret = dev_set_name(dev, "%s.%s.%d", modname, auxdev->name, auxdev->id);
> >  	if (ret) {
> >  		dev_err(dev, "auxiliary device dev_set_name failed: %d\n", ret);
> > +		ida_free(&auxiliary_id, auxdev->id);
> >  		return ret;
> >  	}
> >  
> >  	ret = device_add(dev);
> > -	if (ret)
> > +	if (ret) {
> >  		dev_err(dev, "adding auxiliary device failed!: %d\n", ret);
> > +		ida_free(&auxiliary_id, auxdev->id);
> > +	}
> >  
> >  	return ret;
> >  }
> >  EXPORT_SYMBOL_GPL(__auxiliary_device_add);
> >  
> > +void auxiliary_device_delete(struct auxiliary_device *auxdev)
> > +{
> > +	ida_free(&auxiliary_id, auxdev->id);
> 
> Hm...I wonder if we should call this from the device's release callback instead.

Yes, you are right.

Thanks