Re: [PATCH v4 03/16] powerpc/vas: Add platform specific user window operations

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

On Thu, 2021-06-03 at 14:05 +1000, Nicholas Piggin wrote:
> Excerpts from Haren Myneni's message of May 21, 2021 7:30 pm:
> > PowerNV uses registers to open/close VAS windows, and getting the
> > paste address. Whereas the hypervisor calls are used on PowerVM.
> > 
> > This patch adds the platform specific user space window operations
> > and register with the common VAS user space interface.
> 
> Basic idea makes sense. I don't understand this code in detail
> though.
> A couple of things,
> 
> > Signed-off-by: Haren Myneni <haren@linux.ibm.com>
> > ---
> >  arch/powerpc/include/asm/vas.h              | 14 +++++-
> >  arch/powerpc/platforms/book3s/vas-api.c     | 52 ++++++++++++-----
> > ----
> >  arch/powerpc/platforms/powernv/vas-window.c | 46
> > +++++++++++++++++-
> >  3 files changed, 89 insertions(+), 23 deletions(-)
> > 
> > diff --git a/arch/powerpc/include/asm/vas.h
> > b/arch/powerpc/include/asm/vas.h
> > index 6076adf9ab4f..668303198772 100644
> > --- a/arch/powerpc/include/asm/vas.h
> > +++ b/arch/powerpc/include/asm/vas.h
> > @@ -5,6 +5,7 @@
> >  
> >  #ifndef _ASM_POWERPC_VAS_H
> >  #define _ASM_POWERPC_VAS_H
> > +#include <uapi/asm/vas-api.h>
> >  
> >  struct vas_window;
> >  
> > @@ -48,6 +49,16 @@ enum vas_cop_type {
> >  	VAS_COP_TYPE_MAX,
> >  };
> >  
> > +/*
> > + * User space window operations used for powernv and powerVM
> > + */
> > +struct vas_user_win_ops {
> > +	struct vas_window * (*open_win)(struct vas_tx_win_open_attr *,
> > +				enum vas_cop_type);
> > +	u64 (*paste_addr)(void *);
> > +	int (*close_win)(void *);
> 
> Without looking further into the series, why do these two take void
> * 
> when the first returns a vas_window * which appears to be the
> required
> argument to these?

Yes, vas_window * should be passed instead of void * for paste_addr() /
close_win()

> 
> > +static struct vas_user_win_ops vops =  {
> > +	.open_win	=	vas_user_win_open,
> > +	.paste_addr	=	vas_user_win_paste_addr,
> > +	.close_win	=	vas_user_win_close,
> > +};
> 
> const?
> 
> Thanks,
> Nick