linux-kernel - Re: [Patch v4 05/16] ACPI: Add interfaces to parse IOAPIC ID for IOAPIC hotplug

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Message-ID: <540FB051.3050107@linux.intel.com>
Date:	Wed, 10 Sep 2014 09:58:41 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Grant Likely <grant.likely@...aro.org>,
	Len Brown <lenb@...nel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tony Luck <tony.luck@...el.com>,
	Joerg Roedel <joro@...tes.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	x86@...nel.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: [Patch v4 05/16] ACPI: Add interfaces to parse IOAPIC ID for
 IOAPIC hotplug



On 2014/9/9 18:54, Thomas Gleixner wrote:
> On Thu, 28 Aug 2014, Jiang Liu wrote:
>>  
>> +static struct acpi_table_madt *madt;
>> +static int read_madt;
> 
> Pretty lousy file visible variable names.
> 
> So we end up with two copies of the butt ugly 
> 
>    if (!read_madt) {
>       .....
>    }
> 
> stuff instead of creating a helper function which hides that and do
> 
>       madr = get_madt();
>       if (!madt)
> 		return ...;
> 
> at the call sites.
Thanks for suggestion, will improve in that way.

> 
>>  static int map_lapic_id(struct acpi_subtable_header *entry,
>>  		 u32 acpi_id, int *apic_id)
>>  {
>> @@ -64,8 +71,6 @@ static int map_lsapic_id(struct acpi_subtable_header *entry,
>>  static int map_madt_entry(int type, u32 acpi_id)
>>  {
>>  	unsigned long madt_end, entry;
>> -	static struct acpi_table_madt *madt;
>> -	static int read_madt;
>>  	int apic_id = -1;
>>  
>>  	if (!read_madt) {
>> @@ -200,3 +205,90 @@ int acpi_get_cpuid(acpi_handle handle, int type, u32 acpi_id)
>>  	return acpi_map_cpuid(apic_id, acpi_id);
>>  }
>>  EXPORT_SYMBOL_GPL(acpi_get_cpuid);
>> +
>> +#ifdef CONFIG_ACPI_HOTPLUG_IOAPIC
>> +static int map_ioapic_id(struct acpi_subtable_header *entry, u32 gsi_base,
>> +			 u64 *phys_addr, int *ioapic_id)
>> +{
>> +	struct acpi_madt_io_apic *ioapic = (struct acpi_madt_io_apic *)entry;
>> +
>> +	if (ioapic->global_irq_base != gsi_base)
>> +		return 0;
>> +
>> +	*phys_addr = ioapic->address;
>> +	*ioapic_id = ioapic->id;
>> +	return 1;
>> +}
>> +
>> +static int map_madt_ioapic_entry(u32 gsi_base, u64 *phys_addr)
>> +{
>> +	struct acpi_subtable_header *hdr;
>> +	unsigned long madt_end, entry;
>> +	int apic_id = -1;
>> +
>> +	if (!read_madt) {
>> +		if (ACPI_FAILURE(acpi_get_table(ACPI_SIG_MADT, 0,
>> +					(struct acpi_table_header **)&madt)))
>> +			madt = NULL;
>> +		read_madt++;
>> +	}
>> +
>> +	if (!madt)
>> +		return apic_id;
>> +
>> +	entry = (unsigned long)madt;
>> +	madt_end = entry + madt->header.length;
>> +
>> +	/* Parse all entries looking for a match. */
>> +	entry += sizeof(struct acpi_table_madt);
>> +	while (entry + sizeof(struct acpi_subtable_header) < madt_end) {
>> +		hdr = (struct acpi_subtable_header *)entry;
>> +		if (hdr->type == ACPI_MADT_TYPE_IO_APIC &&
>> +		    map_ioapic_id(hdr, gsi_base, phys_addr, &apic_id))
>> +			break;
>> +		else
>> +			entry += hdr->length;
>> +	}
>> +
>> +	return apic_id;
>> +}
>> +
>> +static int map_mat_ioapic_entry(acpi_handle handle, u32 gsi_base,
>> +				u64 *phys_addr)
>> +{
>> +	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
>> +	union acpi_object *obj;
>> +	struct acpi_subtable_header *header;
>> +	int apic_id = -1;
>> +
>> +	if (ACPI_FAILURE(acpi_evaluate_object(handle, "_MAT", NULL, &buffer)))
>> +		goto exit;
>> +
>> +	if (!buffer.length || !buffer.pointer)
>> +		goto exit;
>> +
>> +	obj = buffer.pointer;
>> +	if (obj->type != ACPI_TYPE_BUFFER ||
>> +	    obj->buffer.length < sizeof(struct acpi_subtable_header))
>> +		goto exit;
>> +
>> +	header = (struct acpi_subtable_header *)obj->buffer.pointer;
>> +	if (header->type == ACPI_MADT_TYPE_IO_APIC)
>> +		map_ioapic_id(header, gsi_base, phys_addr, &apic_id);
>> +
>> +exit:
>> +	kfree(buffer.pointer);
>> +	return apic_id;
>> +}
> 
> 
> This stuff really wants proper documentation. The lack of comments is
> just annoying.
Sure, will improve comments in next version.

Regards!
Gerry

> 
>> +int acpi_get_ioapic_id(acpi_handle handle, u32 gsi_base, u64 *phys_addr)
>> +{
>> +	int apic_id;
>> +
>> +	apic_id = map_mat_ioapic_entry(handle, gsi_base, phys_addr);
>> +	if (apic_id == -1)
>> +		apic_id = map_madt_ioapic_entry(gsi_base, phys_addr);
>> +
>> +	return apic_id;
>> +}
> 
> Thanks,
> 
> 	tglx
> 
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