linux-kernel - Re: [PATCH v2 0/7] syscore: Pass context data to callbacks

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Message-ID: <l54i36uk33je744w4f47tehdopk5dsjotvozfv5b2hehmxrwpq@eins7awyq4dy>
Date: Tue, 22 Jul 2025 15:56:40 +0200
From: Thierry Reding <thierry.reding@...il.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: x86@...nel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-riscv@...ts.infradead.org, linux-mips@...r.kernel.org, loongarch@...ts.linux.dev, 
	linuxppc-dev@...ts.ozlabs.org, linux-sh@...r.kernel.org, linux-pci@...r.kernel.org, 
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/7] syscore: Pass context data to callbacks

On Sat, Jul 19, 2025 at 08:52:41AM +0200, Greg Kroah-Hartman wrote:
> On Fri, Jul 18, 2025 at 03:49:37PM +0200, Thierry Reding wrote:
> > On Thu, Jul 17, 2025 at 02:11:41PM +0200, Greg Kroah-Hartman wrote:
> > > On Thu, Jul 17, 2025 at 12:32:34PM +0200, Thierry Reding wrote:
[...]
> > 	struct syscore;
> > 
> > 	struct syscore_ops {
> > 		int (*suspend)(struct syscore *syscore);
> > 		void (*resume)(struct syscore *syscore);
> > 		void (*shutdown)(struct syscore *syscore);
> > 	};
> > 
> > 	struct syscore {
> > 		const struct syscore_ops *ops;
> > 		struct list_head node;
> > 	};
> > 
> > Is that what you had in mind?
> 
> I missed the list_head, so yes, this would be better, but don't pass
> back the syscore structure, how about just a void * instead, making the
> whole container_of() stuff go away?

Yeah, that's a possibility. I personally don't like passing the void *
around because it's easier to make mistakes that way. I also find it
unintuitive because it doesn't immediately show you what the functions
expect.

My understanding is that the container_of() should get optimized away
most of the time, so there aren't any obvious downsides that I can see.

But I don't feel very strongly, so if you have a strong preference for
void pointers, I can do that.

Thierry

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