linux-kernel - Re: [PATCH v2] ACPI/IORT: Fix iort_node_get

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Date:   Fri, 03 Feb 2017 10:20:29 +0800
From:   Hanjun Guo <hanjun.guo@...aro.org>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        linux-acpi@...r.kernel.org
CC:     linux-kernel@...r.kernel.org, Sinan Kaya <okaya@...eaurora.org>,
        Tomasz Nowicki <tn@...ihalf.com>,
        Nate Watterson <nwatters@...eaurora.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH v2] ACPI/IORT: Fix iort_node_get_id() mapping entries
 indexing

On 01/10/2017 08:00 PM, Lorenzo Pieralisi wrote:
> Commit 618f535a6062 ("ACPI/IORT: Add single mapping function")
> introduced a function (iort_node_get_id()) to retrieve ids for IORT
> named components.
>
> The iort_node_get_id() takes an index as input to refer to a specific
> mapping entry in the named component IORT node mapping array.
>
> For a mapping entry at a given index, iort_node_get_id() should return
> the id value (through the id_out function parameter) and the IORT node
> output_reference (through function return value) the given mapping entry
> refers to.
>
> Technically output_reference values may differ for different map
> entries, (see diagram below - mapped id values may refer to different eg
> IORT SMMU nodes; the kernel may not be able to handle different
> output_reference values for a given named component but the IORT kernel
> layer should still report the IORT mappings as reported by firmware) but
> current code in iort_node_get_id() fails to use the index function
> parameter to return the correct output_reference value (ie it always
> returns the output_reference value of the first entry in the mapping
> array whilst using the index correctly to retrieve the id value from the
> respective entry).
>
> 	|----------------------|
> 	|     named component  |
> 	|----------------------|
> 	|      map entry[0]    |
> 	|----------------------|
> 	|       id value       |
> 	| output_reference----------------> eg SMMU 1
> 	|----------------------|
> 	|      map entry[1]    |
> 	|----------------------|
> 	|       id value       |
> 	| output_reference----------------> eg SMMU 2
> 	|----------------------|
> 		    .
> 		    .
> 		    .
> 	|----------------------|
> 	|      map entry[N]    |
> 	|----------------------|
> 	|       id value       |
> 	| output_reference----------------> eg SMMU 1
> 	|----------------------|
>
> Consequently the iort_node_get_id() function always returns the IORT
> node pointed at by the output_reference value of the first named
> component mapping array entry, irrespective of the index parameter,
> which is a bug.
>
> Update the map array entry pointer computation in iort_node_get_id() to
> take into account the index value, fixing the issue.
>
> Fixes: 618f535a6062 ("ACPI/IORT: Add single mapping function")
> Reported-by: Hanjun Guo <hanjun.guo@...aro.org>
> Reviewed-by: Hanjun Guo <hanjun.guo@...aro.org>
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
> Cc: Hanjun Guo <hanjun.guo@...aro.org>
> Cc: Sinan Kaya <okaya@...eaurora.org>
> Cc: Tomasz Nowicki <tn@...ihalf.com>
> Cc: Nate Watterson <nwatters@...eaurora.org>
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> ---
> v1 -> v2:
> 	- Updated/improved commit log
> 	- Added review tags

Forgot to mention that I tested this patch on Hisilicon
D03,

Tested-by: Hanjun Guo <hanjun.guo@...aro.org>

BTW, Lorenzo, Rafael, since it's a bugfix, can this be merged into
4.10-rc7?

Thanks
Hanjun