RE: [PATCH v14 1/4] drivers pps/generators: replace copy of pps-gen info struct with const pointer

[Mohan, Subramanian]

> -----Original Message-----
> From: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> Sent: Friday, February 14, 2025 8:25 PM
> To: Mohan, Subramanian <subramanian.mohan@xxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-doc@xxxxxxxxxxxxxxx;
> gregkh@xxxxxxxxxxxxxxxxxxx; giometti@xxxxxxxxxxxx; tglx@xxxxxxxxxxxxx;
> corbet@xxxxxxx; Dong, Eddie <eddie.dong@xxxxxxxxx>; Hall, Christopher S
> <christopher.s.hall@xxxxxxxxx>; N, Pandith <pandith.n@xxxxxxxxx>; T R,
> Thejesh Reddy <thejesh.reddy.t.r@xxxxxxxxx>; Zage, David
> <david.zage@xxxxxxxxx>; Chinnadurai, Srinivasan
> <srinivasan.chinnadurai@xxxxxxxxx>
> Subject: Re: [PATCH v14 1/4] drivers pps/generators: replace copy of pps-gen
> info struct with const pointer
> 
> On Fri, Feb 14, 2025 at 02:37:52PM +0530, subramanian.mohan@xxxxxxxxx
> wrote:
> > From: Subramanian Mohan <subramanian.mohan@xxxxxxxxx>
> >
> > Some PPS generator drivers may need to retrieve a pointer to their
> > internal data while executing the PPS generator enable() method.
> >
> > During the driver registration the pps_gen_device pointer is returned
> > from the framework, and for that reason, there is difficulty in
> > getting generator driver data back in the enable function. We won't be
> > able to use container_of macro as it results in static assert, and we
> > might end up in using static pointer.
> >
> > To solve the issue and to get back the generator driver data back, we
> > should not copy the struct pps_gen_source_info within the struct
> > pps_gen_device during the registration stage, but simply save the
> > pointer of the driver one. In this manner, driver may get a pointer to
> > their internal data as shown below:
> >
> > struct pps_gen_foo_data_s {
> >         ...
> > 	struct pps_gen_source_info gen_info;
> > 	struct pps_gen_device *pps_gen;
> > 	...
> > };
> >
> > static int __init pps_gen_foo_init(void) {
> >         struct pps_gen_foo_data_s *foo;
> > 	...
> >         foo->pps_gen = pps_gen_register_source(&foo->gen_info);
> > 	...
> > }
> >
> > Then, in the enable() method, we can retrieve the pointer to the main
> > struct by using the code below:
> >
> > static int pps_gen_foo_enable(struct pps_gen_device *pps_gen, bool
> > enable) {
> >         struct pps_gen_foo_data_s *foo = container_of(pps_gen->info,
> > 						struct pps_gen_foo_data_s,
> gen_info);
> >         ...
> > }
> 
> Shouldn't Subject start with "pps: generators: ..."?
> 
> With that fixed,
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>

Sure Andy will modify the subject line as suggested and add Reviewed-by tag, Will resend v15 accordingly.

Thanks,
Subbu

> 
> --
> With Best Regards,
> Andy Shevchenko
>