netdev - Re: [PATCH v3 19/20] cxl: add function for obtaining params from a region

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Message-ID: <8afb39a9-c04f-4e61-af75-e7f6adcee36f@intel.com>
Date: Fri, 13 Sep 2024 10:48:25 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: alejandro.lucero-palau@....com, linux-cxl@...r.kernel.org,
 netdev@...r.kernel.org, dan.j.williams@...el.com, martin.habets@...inx.com,
 edward.cree@....com, davem@...emloft.net, kuba@...nel.org,
 pabeni@...hat.com, edumazet@...gle.com
Cc: Alejandro Lucero <alucerop@....com>
Subject: Re: [PATCH v3 19/20] cxl: add function for obtaining params from a
 region



On 9/7/24 1:18 AM, alejandro.lucero-palau@....com wrote:
> From: Alejandro Lucero <alucerop@....com>
> 
> A CXL region struct contains the physical address to work with.
> 
> Add a function for given a opaque cxl region struct returns the params
> to be used for mapping such memory range.
> 
> Signed-off-by: Alejandro Lucero <alucerop@....com>
> ---
>  drivers/cxl/core/region.c | 16 ++++++++++++++++
>  drivers/cxl/cxl.h         |  2 ++
>  include/linux/cxl/cxl.h   |  2 ++
>  3 files changed, 20 insertions(+)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 45b4891035a6..e0e2342bb1ed 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -2662,6 +2662,22 @@ static struct cxl_region *devm_cxl_add_region(struct cxl_root_decoder *cxlrd,
>  	return ERR_PTR(rc);
>  }
>  
> +int cxl_get_region_params(struct cxl_region *region, resource_size_t *start,
> +			  resource_size_t *end)

Maybe just pass in a 'struct range' to be filled out instead of start/end?

> +{
> +	if (!region)
> +		return -ENODEV;
> +
> +	if (!region->params.res)
> +		return -ENOSPC;
> +
> +	*start = region->params.res->start;
> +	*end = region->params.res->end;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_get_region_params, CXL);

I think at least for me, it's better to have the introduction of helper functions to be with the code where it gets called to provide the full picture and thus make a better review. Especially if the function is fairly small. So maybe squash this patch and the next one. There may be a few other situations like this in this series worth the same consideration.
  
> +
>  static ssize_t __create_region_show(struct cxl_root_decoder *cxlrd, char *buf)
>  {
>  	return sysfs_emit(buf, "region%u\n", atomic_read(&cxlrd->region_id));
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 120e961f2e31..b26833ff52c0 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -904,6 +904,8 @@ void cxl_coordinates_combine(struct access_coordinate *out,
>  bool cxl_endpoint_decoder_reset_detected(struct cxl_port *port);
>  
>  int cxl_region_detach(struct cxl_endpoint_decoder *cxled);
> +int cxl_get_region_params(struct cxl_region *region, resource_size_t *start,
> +			  resource_size_t *end);
>  /*
>   * Unit test builds overrides this to __weak, find the 'strong' version
>   * of these symbols in tools/testing/cxl/.
> diff --git a/include/linux/cxl/cxl.h b/include/linux/cxl/cxl.h
> index 169683d75030..ef3bd8329bd8 100644
> --- a/include/linux/cxl/cxl.h
> +++ b/include/linux/cxl/cxl.h
> @@ -76,4 +76,6 @@ struct cxl_region *cxl_create_region(struct cxl_root_decoder *cxlrd,
>  				     struct cxl_endpoint_decoder *cxled);
>  
>  int cxl_region_detach(struct cxl_endpoint_decoder *cxled);
> +int cxl_get_region_params(struct cxl_region *region, resource_size_t *start,
> +			  resource_size_t *end);
>  #endif