Re: [PATCH v2] powerpc: vas-api: constify dynamic struct class in coproc api register

[Haren Myneni <haren@linux.ibm.com>]

On Wed, 2026-03-11 at 09:23 +0100, Greg KH wrote:
> On Mon, Mar 09, 2026 at 11:48:57AM +0100, Jori Koolstra wrote:
> > My bad, the earlier email went out to soon.
> > 
> > > Op 09-03-2026 07:01 CET schreef Greg KH
> > > <gregkh@linuxfoundation.org>:
> > > >  arch/powerpc/platforms/book3s/vas-api.c | 34
> > > > +++++++++++++++++++------
> > > >  1 file changed, 26 insertions(+), 8 deletions(-)
> > > > 
> > > > diff --git a/arch/powerpc/platforms/book3s/vas-api.c
> > > > b/arch/powerpc/platforms/book3s/vas-api.c
> > > > index ea4ffa63f043..e377981fd533 100644
> > > > --- a/arch/powerpc/platforms/book3s/vas-api.c
> > > > +++ b/arch/powerpc/platforms/book3s/vas-api.c
> > > > @@ -45,7 +45,7 @@ static struct coproc_dev {
> > > >  	struct device *device;
> > > >  	char *name;
> > > >  	dev_t devt;
> > > > -	struct class *class;
> > > > +	const struct class *class;
> > > >  	enum vas_cop_type cop_type;
> > > >  	const struct vas_user_win_ops *vops;
> > > >  } coproc_device;
> > > > @@ -599,6 +599,21 @@ static struct file_operations coproc_fops
> > > > = {
> > > >  	.unlocked_ioctl = coproc_ioctl,
> > > >  };
> > > >  
> > > > +static const struct class nx_gzip_class = {
> > > > +	.name		= "nx-gzip",
> > > > +	.devnode	= coproc_devnode
> > > > +};
> > > > +
> > > > +static const struct class* cop_to_class(enum vas_cop_type cop)
> > > > +{
> > > > +	switch (cop) {
> > > > +	case VAS_COP_TYPE_GZIP:		return
> > > > &nx_gzip_class;
> > > > +	default:
> > > > +		pr_err("No device class defined for cop type
> > > > %d\n", cop);
> > > > +		return NULL;
> > > > +	}
> > > > +}
> > > > +
> > > >  /*
> > > >   * Supporting only nx-gzip coprocessor type now, but this API
> > > > code
> > > >   * extended to other coprocessor types later.
> > > > @@ -609,6 +624,10 @@ int vas_register_coproc_api(struct module
> > > > *mod, enum vas_cop_type cop_type,
> > > >  {
> > > >  	int rc = -EINVAL;
> > > >  	dev_t devno;
> > > > +	const struct class* class = cop_to_class(cop_type);
> > > > +
> > > > +	if (!class)
> > > > +		return rc;
> > > 
> > > How can this happen?
> > > 
> > > This feels odd, are different types of devices being registered
> > > here?  I
> > > don't see where VAS_COP_TYPE_GZIP was being tested in the
> > > original code,
> > > why add this additional logic?
> > > 
> > 
> > My line of thought is this:
> > 
> > There is a function vas_register_coproc_api() that does some kind
> > of registering
> > for different coprocessor types. It has the following comment
> > above:
> > 
> > /*
> >  * Supporting only nx-gzip coprocessor type now, but this API code
> >  * extended to other coprocessor types later.
> >  */
> 
> I guess "later" never happened :(

Yes, VAS is virtual accelerator switchboard which can support multiple
accelerator types. Hence added vas_register_api* interface for
different accelerators. But no plans to add other accelerators on
powerpc right now. So can we use only VAS_COP_TYPE_GZIP class and can
visit later. 


diff --git a/arch/powerpc/platforms/powernv/vas-window.c
b/arch/powerpc/platforms/powernv/vas-window.c
index 9f093176b8db..360fdd8f200e 100644
--- a/arch/powerpc/platforms/powernv/vas-window.c
+++ b/arch/powerpc/platforms/powernv/vas-window.c
@@ -1459,6 +1459,8 @@ static const struct vas_user_win_ops vops =  {
 int vas_register_api_powernv(struct module *mod, enum vas_cop_type
cop_type,
                             const char *name)
 {
+       if (cop_type != VAS_COP_TYPE_GZIP)
+               return -ENOTSUPP;
 
        return vas_register_coproc_api(mod, cop_type, name, &vops);
 }
diff --git a/arch/powerpc/platforms/pseries/vas.c
b/arch/powerpc/platforms/pseries/vas.c
index 9a28f2899716..19e11056e6aa 100644
--- a/arch/powerpc/platforms/pseries/vas.c
+++ b/arch/powerpc/platforms/pseries/vas.c
@@ -574,6 +574,9 @@ int vas_register_api_pseries(struct module *mod,
enum vas_cop_type cop_type,
        if (!copypaste_feat)
                return -ENOTSUPP;
 
+       if (cop_type != VAS_COP_TYPE_GZIP)
+               return -ENOTSUPP;
+
        return vas_register_coproc_api(mod, cop_type, name,
&vops_pseries);
 }
 EXPORT_SYMBOL_GPL(vas_register_api_pseries);

Thanks
Haren