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Message-ID: <560EF1BD.1020004@redhat.com>
Date: Fri, 2 Oct 2015 16:06:05 -0500
From: Wei Huang <wei@...hat.com>
To: Marc Zyngier <marc.zyngier@....com>,
"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>
Cc: 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
Hi Marc,
On 09/28/2015 09:49 AM, Marc Zyngier wrote:
> IRQ controllers and timers are the two types of device the kernel
> requires before being able to use the device driver model.
>
> ACPI so far lacks a proper probing infrastructure similar to the one
> we have with DT, where we're able to declare IRQ chips and
> clocksources inside the driver code, and let the core code pick it up
> and call us back on a match. This leads to all kind of really ugly
> hacks all over the arm64 code and even in the ACPI layer.
>
> In order to allow some basic probing based on the ACPI tables,
> introduce "struct acpi_probe_entry" which contains just enough
> data and callbacks to match a table, an optional subtable, and
> call a probe function. A driver can, at build time, register itself
> and expect being called if the right entry exists in the ACPI
> table.
>
> A acpi_probe_device_table() is provided, taking an identifier for
> a set of acpi_prove_entries, and iterating over the registered
> entries.
>
> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> ---
> drivers/acpi/scan.c | 39 +++++++++++++++++++++++
> include/asm-generic/vmlinux.lds.h | 10 ++++++
> include/linux/acpi.h | 66 +++++++++++++++++++++++++++++++++++++++
> 3 files changed, 115 insertions(+)
>
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index f834b8c..daf9fc8 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -1913,3 +1913,42 @@ int __init acpi_scan_init(void)
> mutex_unlock(&acpi_scan_lock);
> return result;
> }
> +
> +static struct acpi_probe_entry *ape;
> +static int acpi_probe_count;
> +static DEFINE_SPINLOCK(acpi_probe_lock);
> +
> +static int __init acpi_match_madt(struct acpi_subtable_header *header,
> + const unsigned long end)
> +{
> + if (!ape->subtable_valid || ape->subtable_valid(header, ape))
> + if (!ape->probe_subtbl(header, end))
> + acpi_probe_count++;
> +
> + return 0;
> +}
> +
> +int __init __acpi_probe_device_table(struct acpi_probe_entry *ap_head, int nr)
> +{
> + int count = 0;
> +
> + if (acpi_disabled)
> + return 0;
> +
> + spin_lock(&acpi_probe_lock);
> + for (ape = ap_head; nr; ape++, nr--) {
> + if (ACPI_COMPARE_NAME(ACPI_SIG_MADT, ape->id)) {
> + acpi_probe_count = 0;
> + acpi_table_parse_madt(ape->type, acpi_match_madt, 0);
> + count += acpi_probe_count;
> + } else {
> + int res;
> + res = acpi_table_parse(ape->id, ape->probe_table);
> + if (!res)
> + count++;
> + }
> + }
> + spin_unlock(&acpi_probe_lock);
> +
> + return count;
> +}
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index 1781e54..efd7ed1 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -181,6 +181,16 @@
> #define CPUIDLE_METHOD_OF_TABLES() OF_TABLE(CONFIG_CPU_IDLE, cpuidle_method)
> #define EARLYCON_OF_TABLES() OF_TABLE(CONFIG_SERIAL_EARLYCON, earlycon)
>
> +#ifdef CONFIG_ACPI
> +#define ACPI_PROBE_TABLE(name) \
> + . = ALIGN(8); \
> + VMLINUX_SYMBOL(__##name##_acpi_probe_table) = .; \
> + *(__##name##_acpi_probe_table) \
> + VMLINUX_SYMBOL(__##name##_acpi_probe_table_end) = .;
> +#else
> +#define ACPI_PROBE_TABLE(name)
> +#endif
> +
> #define KERNEL_DTB() \
> STRUCT_ALIGN(); \
> VMLINUX_SYMBOL(__dtb_start) = .; \
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index 84e7055..51a96a8 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -787,6 +787,61 @@ int acpi_dev_prop_read(struct acpi_device *adev, const char *propname,
>
> struct fwnode_handle *acpi_get_next_subnode(struct device *dev,
> struct fwnode_handle *subnode);
> +
> +struct acpi_probe_entry;
> +typedef bool (*acpi_probe_entry_validate_subtbl)(struct acpi_subtable_header *,
> + struct acpi_probe_entry *);
> +
> +#define ACPI_TABLE_ID_LEN 5
> +
> +/**
> + * struct acpi_probe_entry - boot-time probing entry
> + * @id: ACPI table name
> + * @type: Optional subtable type to match
> + * (if @id contains subtables)
> + * @subtable_valid: Optional callback to check the validity of
> + * the subtable
> + * @probe_table: Callback to the driver being probed when table
> + * match is successful
> + * @probe_subtbl: Callback to the driver being probed when table and
> + * subtable match (and optional callback is successful)
> + * @driver_data: Sideband data provided back to the driver
> + */
A suggestion: could you add more details to the description above? I couldn't figure how to use it without reading __acpi_probe_device_table(). Something like "if @id matches the one defined in __acpi_probe_device_table(), then probe_subtbl() will be invoked; otherwise probe_table() will be invoked" would be helpful for programmers use this struct.
> +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);
> +#define ACPI_PROBE_TABLE(name) __##name##_acpi_probe_table
> +#define ACPI_PROBE_TABLE_END(name) __##name##_acpi_probe_table_end
> +
> +int __acpi_probe_device_table(struct acpi_probe_entry *start, int nr);
> +
> +#define acpi_probe_device_table(t) \
> + ({ \
> + extern struct acpi_probe_entry ACPI_PROBE_TABLE(t), \
> + ACPI_PROBE_TABLE_END(t); \
> + __acpi_probe_device_table(&ACPI_PROBE_TABLE(t), \
> + (&ACPI_PROBE_TABLE_END(t) - \
> + &ACPI_PROBE_TABLE(t))); \
> + })
> #else
> static inline int acpi_dev_get_property(struct acpi_device *adev,
> const char *name, acpi_object_type type,
> @@ -845,6 +900,17 @@ static inline struct fwnode_handle *acpi_get_next_subnode(struct device *dev,
> {
> return NULL;
> }
> +
> +#define ACPI_DECLARE_PROBE_ENTRY(table, name, table_id, subtable, validate, data, fn) \
> + static const void * __acpi_table_##name[] \
> + __attribute__((unused)) \
> + = { (void *) table_id, \
> + (void *) subtable, \
> + (void *) valid, \
> + (void *) fn, \
> + (void *) data }
> +
> +#define acpi_probe_device_table(t) ({ int __r = 0; __r;})
> #endif
>
> #endif /*_LINUX_ACPI_H*/
>
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