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SubjectRe: [PATCH] pstore/ram: Rework logic for detecting ramoops
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Hi Kees,

Thanks for your comments.

On 1/13/2023 3:09 AM, Kees Cook wrote:
> On Wed, Jan 11, 2023 at 02:37:45PM +0530, Mukesh Ojha wrote:
>> The reserved memory region for ramoops is assumed to be at a fixed
>> and known location when read from the devicetree. This is not desirable
>> in environments where it is preferred the region to be dynamically
>> allocated at runtime, as opposed to being fixed at compile time.
>>
>> Also, Some of the platforms might be still expecting dedicated
>> memory region for ramoops node where the region is known
>> beforehand and platform_get_resource() is used in that case.
>>
>> So, Add logic to detect the start and size of the ramoops memory
>> region by looking up reserved memory region with
>> of_reserved_mem_lookup() when platform_get_resource() failed.
>>
>> Signed-off-by: Mukesh Ojha <quic_mojha@quicinc.com>
>
> Thanks for the patch! Notes below...
>
>> ---
>> fs/pstore/ram.c | 19 ++++++++++++++-----
>> 1 file changed, 14 insertions(+), 5 deletions(-)
>>
>> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
>> index ade66db..e4bbba1 100644
>> --- a/fs/pstore/ram.c
>> +++ b/fs/pstore/ram.c
>> @@ -20,6 +20,7 @@
>> #include <linux/compiler.h>
>> #include <linux/of.h>
>> #include <linux/of_address.h>
>> +#include <linux/of_reserved_mem.h>
>>
>> #include "internal.h"
>> #include "ram_internal.h"
>> @@ -643,6 +644,7 @@ static int ramoops_parse_dt(struct platform_device *pdev,
>> {
>> struct device_node *of_node = pdev->dev.of_node;
>> struct device_node *parent_node;
>> + struct reserved_mem *rmem;
>> struct resource *res;
>> u32 value;
>> int ret;
>> @@ -651,13 +653,20 @@ static int ramoops_parse_dt(struct platform_device *pdev,
>>
>> res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> if (!res) {
>> - dev_err(&pdev->dev,
>> - "failed to locate DT /reserved-memory resource\n");
>> - return -EINVAL;
>> + rmem = of_reserved_mem_lookup(of_node);
>> + if (rmem) {
>> + pdata->mem_size = rmem->size;
>> + pdata->mem_address = rmem->base;
>> + } else {
>> + dev_err(&pdev->dev,
>> + "failed to locate DT /reserved-memory resource\n");
>> + return -EINVAL;
>> + }
>
> Since the "else" case returns, the traditional code pattern is to leave
> the other case "inline" (an indented), like so:
>
> if (!rmem) {
> dev_err(&pdev->dev,
> "failed to locate DT /reserved-memory resource\n");
> return -EINVAL;
> }
> pdata->mem_size = rmem->size;
> pdata->mem_address = rmem->base;
>

Fixed it in v2.

>
>> + } else {
>> + pdata->mem_size = resource_size(res);
>> + pdata->mem_address = res->start;
>> }
>
> Since this change the potential interface with DT, can you also update
> the documentation in:
>
> Documentation/devicetree/bindings/reserved-memory/ramoops.yaml
>
> Or maybe my understanding of DT parsing is lacking and this change is
> doing something slightly different?
>

Have updated the docs in v2;

-Mukesh

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