netdev - Re: [PATCH v18 11/20] cxl: Define a driver interface for DPA allocation

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Message-ID: <9f296075-dece-449c-9cf2-cbd080846755@amd.com>
Date: Thu, 25 Sep 2025 10:25:34 +0100
From: Alejandro Lucero Palau <alucerop@....com>
To: "Cheatham, Benjamin" <benjamin.cheatham@....com>,
 alejandro.lucero-palau@....com
Cc: linux-cxl@...r.kernel.org, netdev@...r.kernel.org,
 dan.j.williams@...el.com, edward.cree@....com, davem@...emloft.net,
 kuba@...nel.org, pabeni@...hat.com, edumazet@...gle.com, dave.jiang@...el.com
Subject: Re: [PATCH v18 11/20] cxl: Define a driver interface for DPA
 allocation


On 9/22/25 22:09, Cheatham, Benjamin wrote:
> On 9/18/2025 4:17 AM, alejandro.lucero-palau@....com wrote:
>> From: Alejandro Lucero <alucerop@....com>
>>
>> Region creation involves finding available DPA (device-physical-address)
>> capacity to map into HPA (host-physical-address) space.
>>
>> In order to support CXL Type2 devices, define an API, cxl_request_dpa(),
>> that tries to allocate the DPA memory the driver requires to operate.The
>> memory requested should not be bigger than the max available HPA obtained
>> previously with cxl_get_hpa_freespace().
>>
>> Based on https://lore.kernel.org/linux-cxl/168592158743.1948938.7622563891193802610.stgit@dwillia2-xfh.jf.intel.com/
>>
>> Signed-off-by: Alejandro Lucero <alucerop@....com>
>> ---
>>   drivers/cxl/core/hdm.c | 83 ++++++++++++++++++++++++++++++++++++++++++
>>   drivers/cxl/cxl.h      |  1 +
>>   include/cxl/cxl.h      |  5 +++
>>   3 files changed, 89 insertions(+)
>>
>> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
>> index e9e1d555cec6..d1b1d8ab348a 100644
>> --- a/drivers/cxl/core/hdm.c
>> +++ b/drivers/cxl/core/hdm.c
>> @@ -3,6 +3,7 @@
>>   #include <linux/seq_file.h>
>>   #include <linux/device.h>
>>   #include <linux/delay.h>
>> +#include <cxl/cxl.h>
>>   
>>   #include "cxlmem.h"
>>   #include "core.h"
>> @@ -556,6 +557,13 @@ bool cxl_resource_contains_addr(const struct resource *res, const resource_size_
>>   	return resource_contains(res, &_addr);
>>   }
>>   
>> +/**
>> + * cxl_dpa_free - release DPA (Device Physical Address)
>> + *
>> + * @cxled: endpoint decoder linked to the DPA
>> + *
>> + * Returns 0 or error.
>> + */
> Don't think you need this comment; it's not adding anything you can't get by just looking
> at the function header.


I think this is needed for proper docs generation even for the universal 
and simple int return.