Shipping versions of the cxl-cli utility expect all regions to have a 'uuid' attribute. In preparation for 'ram' regions, update the 'uuid' attribute to return an empty string which satisfies the current expectations of 'cxl list -R'. Otherwise, 'cxl list -R' fails in the presence of regions with the 'uuid' attribute missing. Force the attribute to be read-only as there is no facility or expectation for a 'ram' region to recall its uuid from one boot to the next. Reviewed-by: Vishal Verma <vishal.l.verma@xxxxxxxxx> Tested-by: Fan Ni <fan.ni@xxxxxxxxxxx> Link: https://lore.kernel.org/r/167564536587.847146.12703125206459604597.stgit@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> --- Documentation/ABI/testing/sysfs-bus-cxl | 3 ++- drivers/cxl/core/region.c | 11 +++++++++-- 2 files changed, 11 insertions(+), 3 deletions(-) diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl index 058b0c45001f..4c4e1cbb1169 100644 --- a/Documentation/ABI/testing/sysfs-bus-cxl +++ b/Documentation/ABI/testing/sysfs-bus-cxl @@ -317,7 +317,8 @@ Contact: linux-cxl@xxxxxxxxxxxxxxx Description: (RW) Write a unique identifier for the region. This field must be set for persistent regions and it must not conflict with the - UUID of another region. + UUID of another region. For volatile ram regions this + attribute is a read-only empty string. What: /sys/bus/cxl/devices/regionZ/interleave_granularity diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c index 17d2d0c12725..0fc80478ff6b 100644 --- a/drivers/cxl/core/region.c +++ b/drivers/cxl/core/region.c @@ -45,7 +45,10 @@ static ssize_t uuid_show(struct device *dev, struct device_attribute *attr, rc = down_read_interruptible(&cxl_region_rwsem); if (rc) return rc; - rc = sysfs_emit(buf, "%pUb\n", &p->uuid); + if (cxlr->mode != CXL_DECODER_PMEM) + rc = sysfs_emit(buf, "\n"); + else + rc = sysfs_emit(buf, "%pUb\n", &p->uuid); up_read(&cxl_region_rwsem); return rc; @@ -300,8 +303,12 @@ static umode_t cxl_region_visible(struct kobject *kobj, struct attribute *a, struct device *dev = kobj_to_dev(kobj); struct cxl_region *cxlr = to_cxl_region(dev); + /* + * Support tooling that expects to find a 'uuid' attribute for all + * regions regardless of mode. + */ if (a == &dev_attr_uuid.attr && cxlr->mode != CXL_DECODER_PMEM) - return 0; + return 0444; return a->mode; }
