On Wed, Jan 16, 2019 at 09:14:33AM -0700, Mathieu Poirier wrote:

On Wed, 16 Jan 2019 at 08:39, Greg KH [off-list ref] wrote:

quoted

On Tue, Jan 15, 2019 at 04:07:37PM -0700, Mathieu Poirier wrote:

quoted

Add a "sinks" directory entry so that users can see all the sinks
available in the system in a single place.  Individual sink are added
as they are registered with the coresight bus.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 .../hwtracing/coresight/coresight-etm-perf.c  | 43 +++++++++++++++++++
 .../hwtracing/coresight/coresight-etm-perf.h  |  1 +
 drivers/hwtracing/coresight/coresight.c       | 17 ++++++++
 3 files changed, 61 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index f21eb28b6782..292bd409a68c 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c

@@ -14,6 +14,7 @@
 #include <linux/perf_event.h>
 #include <linux/percpu-defs.h>
 #include <linux/slab.h>
+#include <linux/stringhash.h>
 #include <linux/types.h>
 #include <linux/workqueue.h>

@@ -43,8 +44,18 @@ static const struct attribute_group etm_pmu_format_group = {
      .attrs  = etm_config_formats_attr,
 };

+static struct attribute *etm_config_sinks_attr[] = {
+     NULL,
+};
+
+static const struct attribute_group etm_pmu_sinks_group = {
+     .name   = "sinks",
+     .attrs  = etm_config_sinks_attr,
+};
+
 static const struct attribute_group *etm_pmu_attr_groups[] = {
      &etm_pmu_format_group,
+     &etm_pmu_sinks_group,
      NULL,
 };

@@ -479,6 +490,38 @@ int etm_perf_symlink(struct coresight_device *csdev, bool link)
      return 0;
 }

+static ssize_t etm_perf_sink_name_show(struct device *dev,
+                                    struct device_attribute *dattr,
+                                    char *buf)
+{
+     /* See function coresight_sink_by_id() to know where this is used */
+     u32 hash = hashlen_hash(hashlen_string(NULL, dattr->attr.name));
+
+     return scnprintf(buf, PAGE_SIZE, "%x\n", hash);
+}
+
+int etm_perf_symlink_sink(struct coresight_device *csdev)
+{
+     struct device *pmu_dev = etm_pmu.dev;
+     struct device *pdev = csdev->dev.parent;
+     struct device_attribute *dev_attr;
+
+     if (csdev->type != CORESIGHT_DEV_TYPE_SINK &&
+         csdev->type != CORESIGHT_DEV_TYPE_LINKSINK)
+             return -EINVAL;
+
+     if (!etm_perf_up)
+             return -EPROBE_DEFER;
+
+     dev_attr = kzalloc(sizeof(*dev_attr), GFP_KERNEL);
+     dev_attr->attr.name = kstrdup(dev_name(pdev), GFP_KERNEL);
+     dev_attr->attr.mode = 0444;
+     dev_attr->show = etm_perf_sink_name_show;
+
+     return sysfs_add_file_to_group(&pmu_dev->kobj,
+                                    &dev_attr->attr, "sinks");

What is so odd about this call that you needed me to review this?

As far as I can tell nobody is feeding a dynamic struct attribute to
the function and I wasn't sure if it was because they were told not to
or simply because it wasn't needed, hence asking for a second opinion.

Ah.  Well, again, this is a good question to answer:

quoted

And what happens if this call fails, do you leak memory?

And also, what happens when you unload the device, who frees the
attribute's memory?

thanks,

greg k-h

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