linux-kernel - Re: [PATCH] amba: make amba

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Message-ID: <ZsxbjnMa8teJ5_Pg@smile.fi.intel.com>
Date: Mon, 26 Aug 2024 13:40:14 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Kunwu Chan <kunwu.chan@...ux.dev>
Cc: linux@...linux.org.uk, krzk@...nel.org, andi.shyti@...nel.org,
	robh@...nel.org, gregkh@...uxfoundation.org, suzuki.poulose@....com,
	rmk+kernel@...linux.org.uk, linux-kernel@...r.kernel.org,
	Kunwu Chan <chentao@...inos.cn>
Subject: Re: [PATCH] amba: make amba_bustype constant

On Mon, Aug 26, 2024 at 06:08:11PM +0800, Kunwu Chan wrote:
> On 2024/8/23 21:48, Andy Shevchenko wrote:
> > On Fri, Aug 23, 2024 at 02:42:03PM +0800, Kunwu Chan wrote:

...

> > > -extern struct bus_type amba_bustype;
> > > +extern const struct bus_type amba_bustype;
> > Can we actually hide this from the outside, i.e. make it static in the C file,
> > and introduce the dev_is_amba() helper instead?
> > 
> > P.S. You may look at the PNP bus case (some of the latest patches there)
> 
> I found it problematic in the process of making changes.
> 
> There have some usage of amba_bustype outside the AMBA code ,i.e:
> https://elixir.bootlin.com/linux/v6.10.4/source/drivers/iommu/iommu.c#L155
> 
> So, If we make the amba_bustype inside the AMBA code, the outside cannot
> access.

Yes, that's the idea.

> If only internal access is allowed, it will compile and report an error, how
> should I modify it next, and any suggestions?

Make it patch series:
1) patch that introduces exported function called dev_is_amba() (1 patch);
2) convert user-by-user (N patches);
3) hide the bus type and make it constant.

-- 
With Best Regards,
Andy Shevchenko