RE: [PATCH v3 1/8] cxl: break out range register decoding from cxl_hdm_decode_init()

[Dan Williams <dan.j.williams@intel.com>]

Dave Jiang wrote:
> There are 2 scenarios that requires additional handling. 1. A device that
> has active ranges in DVSEC range registers (RR) but no HDM decoder register
> block. 2. A device that has both RR active and HDM, but the HDM decoders
> are not programmed. The goal is to create emulated decoder software structs
> based on the RR.
> 
> Move the CXL DVSEC range register decoding code block from
> cxl_hdm_decode_init() to its own function. Refactor code in preparation for
> the HDM decoder emulation.  There is no functionality change to the code.
> Name the new function to cxl_dvsec_rr_decode().
> 
> The only change is to set range->start and range->end to CXL_RESOURCE_NONE
> and skipping the reading of base registers if the range size is 0, which
> equates to range not active.
> 
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> 
> ---
> v2:
> - Refactor to continue when size is 0. (Jonathan)
> ---
>  drivers/cxl/core/pci.c |   63 ++++++++++++++++++++++++++++++------------------
>  1 file changed, 40 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> index 57764e9cd19d..a8ecc6ddb3d7 100644
> --- a/drivers/cxl/core/pci.c
> +++ b/drivers/cxl/core/pci.c
[..]
> @@ -410,6 +400,13 @@ int cxl_hdm_decode_init(struct cxl_dev_state *cxlds, struct cxl_hdm *cxlhdm)
>  			return rc;
>  
>  		size |= temp & CXL_DVSEC_MEM_SIZE_LOW_MASK;
> +		if (!size) {
> +			info->dvsec_range[i] = (struct range) {
> +				.start = CXL_RESOURCE_NONE,
> +				.end = CXL_RESOURCE_NONE,
> +			};

This should just be .start = 0, and .end = -1, or .start =
CXL_RESOURCE_NONE, and .end = CXL_RESOURCE_NONE - 1, right? Otherwise,
range_len() on this range will be non-zero. Likely moot because the
range will be skipped because @ranges++ gets skipped, but it looks
strange written this way.