linux-kernel - Re: [RFC PATCH 15/20] cxl: Add a routine to find cxl root decoder on cxl bus

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Message-ID: <439928219.101750944183843.JavaMail.epsvc@epcpadp2new>
Date: Thu, 26 Jun 2025 16:08:38 +0530
From: Neeraj Kumar <s.neeraj@...sung.com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: dan.j.williams@...el.com, dave@...olabs.net, dave.jiang@...el.com,
	alison.schofield@...el.com, vishal.l.verma@...el.com, ira.weiny@...el.com,
	a.manzanares@...sung.com, nifan.cxl@...il.com, anisa.su@...sung.com,
	vishak.g@...sung.com, krish.reddy@...sung.com, arun.george@...sung.com,
	alok.rathore@...sung.com, neeraj.kernel@...il.com,
	linux-kernel@...r.kernel.org, linux-cxl@...r.kernel.org,
	nvdimm@...ts.linux.dev, gost.dev@...sung.com, cpgs@...sung.com
Subject: Re: [RFC PATCH 15/20] cxl: Add a routine to find cxl root decoder
 on cxl bus

On 23/06/25 10:44AM, Jonathan Cameron wrote:
>On Tue, 17 Jun 2025 18:09:39 +0530
>Neeraj Kumar <s.neeraj@...sung.com> wrote:
>
>> Add cxl_find_root_decoder to find root decoder on cxl bus. It is used to
>> find root decoder during region creation
>>
>> Signed-off-by: Neeraj Kumar <s.neeraj@...sung.com>
>> ---
>>  drivers/cxl/core/port.c | 26 ++++++++++++++++++++++++++
>>  drivers/cxl/cxl.h       |  1 +
>>  2 files changed, 27 insertions(+)
>>
>> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
>> index 2452f7c15b2d..94d9322b8e38 100644
>> --- a/drivers/cxl/core/port.c
>> +++ b/drivers/cxl/core/port.c
>> @@ -513,6 +513,32 @@ struct cxl_switch_decoder *to_cxl_switch_decoder(struct device *dev)
>>  }
>>  EXPORT_SYMBOL_NS_GPL(to_cxl_switch_decoder, "CXL");
>>
>> +static int match_root_decoder(struct device *dev, void *data)
>> +{
>> +	return is_root_decoder(dev);
>> +}
>> +
>> +/**
>> + * cxl_find_root_decoder() - find a cxl root decoder on cxl bus
>> + * @port: any descendant port in root-cxl-port topology
>> + */
>> +struct cxl_root_decoder *cxl_find_root_decoder(struct cxl_port *port)
>> +{
>> +	struct cxl_root *cxl_root __free(put_cxl_root) = find_cxl_root(port);
>> +	struct device *dev;
>> +
>> +	if (!cxl_root)
>> +		return NULL;
>> +
>> +	dev = device_find_child(&cxl_root->port.dev, NULL, match_root_decoder);
>> +
>
>No blank line here.  Generally when we have a call then an error check
>it is easier to see how they are related if we keep them in one block.
>

Thanks, Will fix it in V1

>> +	if (!dev)
>> +		return NULL;
>> +
>> +	return to_cxl_root_decoder(dev);
>> +}
>> +EXPORT_SYMBOL_NS_GPL(cxl_find_root_decoder, "CXL");
>> +
>>  static void cxl_ep_release(struct cxl_ep *ep)
>>  {
>>  	put_device(ep->ep);
>> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
>> index 30c80e04cb27..2c6a782d0941 100644
>> --- a/drivers/cxl/cxl.h
>> +++ b/drivers/cxl/cxl.h
>> @@ -871,6 +871,7 @@ bool is_cxl_nvdimm_bridge(struct device *dev);
>>  int devm_cxl_add_nvdimm(struct cxl_port *parent_port, struct cxl_memdev *cxlmd);
>>  struct cxl_nvdimm_bridge *cxl_find_nvdimm_bridge(struct cxl_port *port);
>>  void cxl_region_discovery(struct cxl_port *port);
>> +struct cxl_root_decoder *cxl_find_root_decoder(struct cxl_port *port);
>>
>>  #ifdef CONFIG_CXL_REGION
>>  bool is_cxl_pmem_region(struct device *dev);
>