linux-kernel - Re: [PATCH V7 1/8] ACPI: I/O Remapping Table (IORT) initial support

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Message-ID: <576A6D7F.6010407@arm.com>
Date:	Wed, 22 Jun 2016 11:50:39 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	Hanjun Guo <hanjun.guo@...aro.org>,
	Tomasz Nowicki <tn@...ihalf.com>, tglx@...utronix.de,
	jason@...edaemon.net, rjw@...ysocki.net, bhelgaas@...gle.com,
	lorenzo.pieralisi@....com, robert.richter@...iumnetworks.com,
	shijie.huang@....com, Suravee.Suthikulpanit@....com
Cc:	al.stone@...aro.org, mw@...ihalf.com, graeme.gregory@...aro.org,
	Catalin.Marinas@....com, will.deacon@....com,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, ddaney.cavm@...il.com,
	okaya@...eaurora.org, andrea.gallo@...aro.org,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH V7 1/8] ACPI: I/O Remapping Table (IORT) initial support

On 21/06/16 08:12, Hanjun Guo wrote:
> Hi Tomasz,
> 
> Sorry for jumping out late, just one comment below.
> 
> On 2016/6/20 19:02, Tomasz Nowicki wrote:
>> IORT shows representation of IO topology for ARM based systems.
>> It describes how various components are connected together on
>> parent-child basis e.g. PCI RC -> SMMU -> ITS. Also see IORT spec.
>>
>> Initial support allows to detect IORT table presence and save its
>> root pointer obtained through acpi_get_table(). The pointer validity
>> depends on acpi_gbl_permanent_mmap because if acpi_gbl_permanent_mmap
>> is not set while using IORT nodes we would dereference unmapped pointers.
>>
>> For the aforementioned reason call iort_table_detect() from acpi_init()
>> which guarantees acpi_gbl_permanent_mmap to be set at that point.
>>
>> Add generic helpers which are helpful for scanning and retrieving
>> information from IORT table content. List of the most important helpers:
>> - iort_find_dev_node() finds IORT node for a given device
>> - iort_node_map_rid() maps device RID and returns IORT node which provides
>>   final translation
>>
>> Signed-off-by: Tomasz Nowicki <tn@...ihalf.com>
>> ---
>>  drivers/acpi/Kconfig  |   3 +
>>  drivers/acpi/Makefile |   1 +
>>  drivers/acpi/bus.c    |   2 +
>>  drivers/acpi/iort.c   | 220 ++++++++++++++++++++++++++++++++++++++++++++++++++
>>  include/linux/iort.h  |  30 +++++++
> 
> [...]
> 
>> +static acpi_status
>> +iort_match_node_callback(struct acpi_iort_node *node, void *context)
>> +{
>> +	struct device *dev = context;
>> +
>> +	switch (node->type) {
>> +	case ACPI_IORT_NODE_NAMED_COMPONENT: {
>> +		struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> 
> ACPI_ALLOCATE_BUFFER is used here, so ...
> 
>> +		struct acpi_device *adev = to_acpi_device_node(dev->fwnode);
>> +		struct acpi_iort_named_component *ncomp;
>> +
>> +		if (!adev)
>> +			break;
>> +
>> +		ncomp = (struct acpi_iort_named_component *)node->node_data;
>> +
>> +		if (ACPI_FAILURE(acpi_get_name(adev->handle,
>> +					       ACPI_FULL_PATHNAME, &buffer))) {
>> +			dev_warn(dev, "Can't get device full path name\n");
>> +			break;
>> +		}
>> +
>> +		if (!strcmp(ncomp->device_name, (char *)buffer.pointer))
>> +			return AE_OK;
> 
> ... we need to kfree(buffer.pointer) before we return or break.

For the record, I've queued this patch on top:

diff --git a/drivers/acpi/iort.c b/drivers/acpi/iort.c
index 496dcf6..3b9e55b 100644
--- a/drivers/acpi/iort.c
+++ b/drivers/acpi/iort.c
@@ -158,11 +158,15 @@ iort_match_node_callback(struct acpi_iort_node *node, void *context)
 		if (ACPI_FAILURE(acpi_get_name(adev->handle,
 					       ACPI_FULL_PATHNAME, &buffer))) {
 			dev_warn(dev, "Can't get device full path name\n");
-			break;
-		}
+		} else {
+			int match;
 
-		if (!strcmp(ncomp->device_name, (char *)buffer.pointer))
-			return AE_OK;
+			match = !strcmp(ncomp->device_name, buffer.pointer);
+			acpi_os_free(&buffer);
+
+			if (match)
+				return AE_OK;
+		}
 
 		break;
 	}


assuming that Rafael is OK with the general approach, of course.

Thanks,

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