On Sun, 05 Feb 2023 17:02:45 -0800 Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > 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. This is new functionality, so do we need the backwards compatibility? Or does that cxl list -R not just skip these, but fail hard? It's inelegant to have this visible at all (and it confused me when I was running tests as I assumed I needed to poke something in it). If nothing else, good to have a comment to remind us in the code why there is the oddity of setting it to read only. Jonathan > > Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> > --- > Documentation/ABI/testing/sysfs-bus-cxl | 3 ++- > drivers/cxl/core/region.c | 7 +++++-- > 2 files changed, 7 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..c9e7f05caa0f 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; > @@ -301,7 +304,7 @@ static umode_t cxl_region_visible(struct kobject *kobj, struct attribute *a, > struct cxl_region *cxlr = to_cxl_region(dev); > > if (a == &dev_attr_uuid.attr && cxlr->mode != CXL_DECODER_PMEM) > - return 0; > + return 0444; Definitely a comment here as this is very odd and we may forget why it is like this. > return a->mode; > } > >
