Re: [PATCH 1/4] ndctl: add cxl bus detection

["Verma, Vishal L" <vishal.l.verma@intel.com>]

On Wed, 2022-09-21 at 14:02 -0700, Dave Jiang wrote:
> Add helper function to detect that the bus is cxl based.

Capitalize CXL in subject and here. This can probably be "Add a CXL bus
type, and detect whether a 'dimm' is backed by the CXL subsystem"

Otherwise looks good.

> 
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> ---
>  ndctl/lib/libndctl.c   |   53 ++++++++++++++++++++++++++++++++++++++++++++++++
>  ndctl/lib/libndctl.sym |    1 +
>  ndctl/lib/private.h    |    1 +
>  ndctl/libndctl.h       |    1 +
>  4 files changed, 56 insertions(+)
> 
> diff --git a/ndctl/lib/libndctl.c b/ndctl/lib/libndctl.c
> index ad54f0626510..10422e24d38b 100644
> --- a/ndctl/lib/libndctl.c
> +++ b/ndctl/lib/libndctl.c
> @@ -12,6 +12,7 @@
>  #include <ctype.h>
>  #include <fcntl.h>
>  #include <dirent.h>
> +#include <libgen.h>
>  #include <sys/stat.h>
>  #include <sys/types.h>
>  #include <sys/ioctl.h>
> @@ -876,6 +877,48 @@ static enum ndctl_fwa_method fwa_method_to_method(const char *fwa_method)
>         return NDCTL_FWA_METHOD_RESET;
>  }
>  
> +static int is_ndbus_cxl(const char *ctl_base)
> +{
> +       char *path, *ppath, *subsys;
> +       char tmp_path[PATH_MAX];
> +       int rc;
> +
> +       /* get the real path of ctl_base */
> +       path = realpath(ctl_base, NULL);
> +       if (!path)
> +               return -errno;
> +
> +       /* setup to get the nd bridge device backing the ctl */
> +       sprintf(tmp_path, "%s/device", path);
> +       free(path);
> +
> +       path = realpath(tmp_path, NULL);
> +       if (!path)
> +               return -errno;
> +
> +       /* get the parent dir of the ndbus, which should be the nvdimm-bridge */
> +       ppath = dirname(path);
> +
> +       /* setup to get the subsystem of the nvdimm-bridge */
> +       sprintf(tmp_path, "%s/%s", ppath, "subsystem");
> +       free(path);
> +
> +       path = realpath(tmp_path, NULL);
> +       if (!path)
> +               return -errno;
> +
> +       subsys = basename(path);
> +
> +       /* check if subsystem is cxl */
> +       if (!strcmp(subsys, "cxl"))
> +               rc = 1;
> +       else
> +               rc = 0;
> +
> +       free(path);
> +       return rc;
> +}
> +
>  static void *add_bus(void *parent, int id, const char *ctl_base)
>  {
>         char buf[SYSFS_ATTR_SIZE];
> @@ -919,6 +962,11 @@ static void *add_bus(void *parent, int id, const char *ctl_base)
>         else
>                 bus->has_of_node = 1;
>  
> +       if (is_ndbus_cxl(ctl_base))
> +               bus->has_cxl = 1;
> +       else
> +               bus->has_cxl = 0;
> +
>         sprintf(path, "%s/device/nfit/dsm_mask", ctl_base);
>         if (sysfs_read_attr(ctx, path, buf) < 0)
>                 bus->nfit_dsm_mask = 0;
> @@ -1050,6 +1098,11 @@ NDCTL_EXPORT int ndctl_bus_has_of_node(struct ndctl_bus *bus)
>         return bus->has_of_node;
>  }
>  
> +NDCTL_EXPORT int ndctl_bus_has_cxl(struct ndctl_bus *bus)
> +{
> +       return bus->has_cxl;
> +}
> +
>  NDCTL_EXPORT int ndctl_bus_is_papr_scm(struct ndctl_bus *bus)
>  {
>         char buf[SYSFS_ATTR_SIZE];
> diff --git a/ndctl/lib/libndctl.sym b/ndctl/lib/libndctl.sym
> index c933163c0380..3a3e8bbd63ef 100644
> --- a/ndctl/lib/libndctl.sym
> +++ b/ndctl/lib/libndctl.sym
> @@ -465,4 +465,5 @@ LIBNDCTL_27 {
>  
>  LIBNDCTL_28 {
>         ndctl_dimm_disable_master_passphrase;
> +       ndctl_bus_has_cxl;
>  } LIBNDCTL_27;
> diff --git a/ndctl/lib/private.h b/ndctl/lib/private.h
> index e5c56295556d..46bc8908bd90 100644
> --- a/ndctl/lib/private.h
> +++ b/ndctl/lib/private.h
> @@ -163,6 +163,7 @@ struct ndctl_bus {
>         int regions_init;
>         int has_nfit;
>         int has_of_node;
> +       int has_cxl;
>         char *bus_path;
>         char *bus_buf;
>         size_t buf_len;
> diff --git a/ndctl/libndctl.h b/ndctl/libndctl.h
> index c52e82a6f826..91ef0f42f654 100644
> --- a/ndctl/libndctl.h
> +++ b/ndctl/libndctl.h
> @@ -133,6 +133,7 @@ struct ndctl_bus *ndctl_bus_get_next(struct ndctl_bus *bus);
>  struct ndctl_ctx *ndctl_bus_get_ctx(struct ndctl_bus *bus);
>  int ndctl_bus_has_nfit(struct ndctl_bus *bus);
>  int ndctl_bus_has_of_node(struct ndctl_bus *bus);
> +int ndctl_bus_has_cxl(struct ndctl_bus *bus);
>  int ndctl_bus_is_papr_scm(struct ndctl_bus *bus);
>  unsigned int ndctl_bus_get_major(struct ndctl_bus *bus);
>  unsigned int ndctl_bus_get_minor(struct ndctl_bus *bus);
> 
>