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SubjectRe: [PATCH v2 1/5] acpi: Add basic device probing infrastructure
Date
On Sunday, September 13, 2015 03:02:19 PM Marc Zyngier wrote:

The subject is slightly confusing IMO (there is a device probing infrastructure
in the ACPI subsystem, but not for the kind of devices in question here).

> 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@arm.com>
> ---
> drivers/acpi/scan.c | 39 +++++++++++++++++++++++
> include/asm-generic/vmlinux.lds.h | 10 ++++++
> include/linux/acpi.h | 65 +++++++++++++++++++++++++++++++++++++++
> 3 files changed, 114 insertions(+)
>
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 01136b8..ac3030b 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -1933,3 +1933,42 @@ 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->validate_subtbl || ape->validate_subtbl(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 7235c48..c63fbda 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -759,6 +759,61 @@ int acpi_dev_prop_read(struct acpi_device *adev, const char *propname,
>
> struct acpi_device *acpi_get_next_child(struct device *dev,
> struct acpi_device *child);
> +
> +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)
> + * @validate_subtbl: Optional callback to check the validity of
> + * the subtable

I'd call this subtbl_valid (or even subtable_valid for that matter, the two extra
vowels in the name don't really hurt IMO).

> + * @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 optionnal callback is successful)

s/optionnal/optional/

> + * @driver_data: Sideband data provided back to the driver
> + */
> +struct acpi_probe_entry {
> + __u8 id[ACPI_TABLE_ID_LEN];
> + __u8 type;
> + acpi_probe_entry_validate_subtbl validate_subtbl;
> + union {
> + acpi_tbl_table_handler probe_table;
> + acpi_tbl_entry_handler probe_subtbl;
> + };
> + kernel_ulong_t driver_data;
> +};
> +
> +#define ACPI_DECLARE(table, name, table_id, subtable, valid, data, fn) \

The name of this macro might be a bit less generic and more self-explaining IMO.

Like ACPI_DECLARE_PROBE_ENTRY()?

> + static const struct acpi_probe_entry __acpi_probe_##name \
> + __used __section(__##table##_acpi_probe_table) \
> + = { \
> + .id = table_id, \
> + .type = subtable, \
> + .validate_subtbl = valid, \
> + .probe_table = (acpi_tbl_table_handler)fn, \
> + .driver_data = data, \
> + }
> +
> +#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,
> @@ -809,6 +864,16 @@ static inline struct acpi_device *acpi_get_next_child(struct device *dev,
> return NULL;
> }
>
> +#define ACPI_DECLARE(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*/
>

Thanks,
Rafael



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