linux-kernel - Re: [PATCH v3 1/7] acpi: Add early device probing infrastructure

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Message-ID: <20151003110402.6aa3022b@arm.com>
Date:	Sat, 3 Oct 2015 11:04:02 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	Wei Huang <wei@...hat.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <lenb@...nel.org>,
	Hanjun Guo <hanjun.guo@...aro.org>,
	Tomasz Nowicki <tomasz.nowicki@...aro.org>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	"Lorenzo Pieralisi" <lorenzo.pieralisi@....com>,
	Sudeep Holla <sudeep.holla@....com>,
	Will Deacon <will.deacon@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	<linaro-acpi@...ts.linaro.org>, <linux-acpi@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 1/7] acpi: Add early device probing infrastructure

On Fri, 2 Oct 2015 16:06:05 -0500
Wei Huang <wei@...hat.com> wrote:

Hi Wei,

> Hi Marc,

[...]

> > +struct acpi_probe_entry {
> > +	__u8 id[ACPI_TABLE_ID_LEN];
> > +	__u8 type;
> > +	acpi_probe_entry_validate_subtbl subtable_valid;
> > +	union {
> > +		acpi_tbl_table_handler probe_table;
> > +		acpi_tbl_entry_handler probe_subtbl;
> > +	};
> 
> Could we avoid using union for probe_table & probe_subtbl? The benefit is that we don't need to do function casting below and compiler can automatically check the correctness.
> 
> > +	kernel_ulong_t driver_data;
> > +};
> > +
> > +#define ACPI_DECLARE_PROBE_ENTRY(table, name, table_id, subtable, valid, data, fn)	\
> > +	static const struct acpi_probe_entry __acpi_probe_##name	\
> > +		__used __section(__##table##_acpi_probe_table)		\
> > +		 = {							\
> > +			.id = table_id,					\
> > +			.type = subtable,				\
> > +			.subtable_valid = valid,			\
> > +			.probe_table = (acpi_tbl_table_handler)fn,	\
> > +			.driver_data = data, 				\
> > +		   }
> > +
> 
> Something like: 
> 
> #define ACPI_DECLARE_PROBE_ENTRY(table, name, table_id, subtable, valid, data, fn, subfn)	\
> 	static const struct acpi_probe_entry __acpi_probe_##name	\
> 		__used __section(__##table##_acpi_probe_table)		\
> 		 = {							\
> 			.id = table_id,					\
> 			.type = subtable,				\
> 			.subtable_valid = valid,			\
> 			.probe_table = fn,				\
> 			.probe_subtbl = subfn,				\
> 			.driver_data = data, 				\
> 		   }
> 
> Then in patch 3, you can define new entries as:
> 
> IRQCHIP_ACPI_DECLARE(gic_v2, ACPI_MADT_TYPE_GENERIC_DISTRIBUTOR,
> 		     gic_validate_dist, ACPI_MADT_GIC_VERSION_V2,
> 		     NULL, gic_v2_acpi_init);
> IRQCHIP_ACPI_DECLARE(gic_v2_maybe, ACPI_MADT_TYPE_GENERIC_DISTRIBUTOR,
> 		     gic_validate_dist, ACPI_MADT_GIC_VERSION_NONE,
> 		     NULL, gic_v2_acpi_init);
> 

That's exactly what I was trying to avoid. If you want to do that, do
it in the IRQCHIP_ACPI_DECLARE macro, as there is strictly no need for
this this NULL to appear here (MADT always matches by subtable).

Or even better, have two ACPI_DECLARE* that populate the probe entry in
a mutually exclusive way (either probe_table is set and both
valid/subtbl are NULL, or probe_table is NULL and the two other fields
are set).

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny.
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