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

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Date:	Tue, 29 Sep 2015 06:30:52 +0200
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
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>
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 04:49 PM, 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);

Isn't supposed 'acpi_table_parse_madt' to return the count ? and 
shouldn't the return code be checked ?

> +			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;
> +}




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