Re: [PATCH v9 04/27] cxl/pci: add check for validating capabilities

Dan Williams
2025-01-18T01:40:56Z

alejandro.lucero-palau@ wrote:
> From: Alejandro Lucero <alucerop@amd.com>
>
> During CXL device initialization supported capabilities by the device
> are discovered. Type3 and Type2 devices have different mandatory
> capabilities and a Type2 expects a specific set including optional
> capabilities.
>
> Add a function for checking expected capabilities against those found
> during initialization and allow those mandatory/expected capabilities to
> be a subset of the capabilities found.
>
> Rely on this function for validating capabilities instead of when CXL
> regs are probed.
>
> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
> Reviewed-by: Zhi Wang <zhiw@nvidia.com>
> ---
> drivers/cxl/core/pci.c | 16 ++++++++++++++++
> drivers/cxl/core/regs.c | 9 ---------
> drivers/cxl/pci.c | 24 ++++++++++++++++++++++++
> include/cxl/cxl.h | 3 +++
> 4 files changed, 43 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
> index ec57caf5b2d7..57318cdc368a 100644
> --- a/drivers/cxl/core/pci.c
> +++ b/drivers/cxl/core/pci.c
> @@ -8,6 +8,7 @@
> #include <linux/pci.h>
> #include <linux/pci-doe.h>
> #include <linux/aer.h>
> +#include <cxl/cxl.h>
> #include <cxlpci.h>
> #include <cxlmem.h>
> #include <cxl.h>
> @@ -1055,3 +1056,18 @@ int cxl_pci_get_bandwidth(struct pci_dev *pdev, struct access_coordinate *c)
>
> return 0;
> }
> +
> +bool cxl_pci_check_caps(struct cxl_dev_state *cxlds, unsigned long *expected_caps,
> + unsigned long *current_caps)
> +{
> +
> + if (current_caps)
> + bitmap_copy(current_caps, cxlds->capabilities, CXL_MAX_CAPS);
> +
> + dev_dbg(cxlds->dev, "Checking cxlds caps 0x%pb vs expected caps 0x%pb\n",
> + cxlds->capabilities, expected_caps);
> +
> + /* Checking a minimum of mandatory/expected capabilities */
> + return bitmap_subset(expected_caps, cxlds->capabilities, CXL_MAX_CAPS);
> +}
> +EXPORT_SYMBOL_NS_GPL(cxl_pci_check_caps, "CXL");

cxl_setup_regs() is already exported from the core. Just make the caller
of cxl_setup_regs() responsible for checking the valid bits per its
constraints rather a new mechanism.