Re: [PATCH v6 2/2] coresight: Add label sysfs node support

From: Suzuki K Poulose
Date: Wed Dec 18 2024 - 13:17:04 EST

Hi Mike

On 18/12/2024 09:56, Mike Leach wrote:
Hi

-----Original Message-----
From: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Sent: Wednesday, December 18, 2024 9:38 AM
To: Mao Jinlong <quic_jinlmao@xxxxxxxxxxx>; Mike Leach
<mike.leach@xxxxxxxxxx>; James Clark <James.Clark@xxxxxxx>; Rob Herring
<robh@xxxxxxxxxx>; Krzysztof Kozlowski <krzk+dt@xxxxxxxxxx>; Conor Dooley
<conor+dt@xxxxxxxxxx>; Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>; Bjorn
Andersson <andersson@xxxxxxxxxx>; Konrad Dybcio
<konradybcio@xxxxxxxxxx>
Cc: coresight@xxxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-arm-
msm@xxxxxxxxxxxxxxx
Subject: Re: [PATCH v6 2/2] coresight: Add label sysfs node support

On 17/12/2024 06:33, Mao Jinlong wrote:
For some coresight components like CTI and TPDM, there could be
numerous of them. From the node name, we can only get the type and
register address of the component. We can't identify the HW or the
system the component belongs to. Add label sysfs node support for
showing the intuitive name of the device.

Signed-off-by: Mao Jinlong <quic_jinlmao@xxxxxxxxxxx>
---
.../testing/sysfs-bus-coresight-devices-cti | 6 ++++
.../sysfs-bus-coresight-devices-funnel | 6 ++++
.../testing/sysfs-bus-coresight-devices-tpdm | 6 ++++
drivers/hwtracing/coresight/coresight-sysfs.c | 32
+++++++++++++++++++
4 files changed, 50 insertions(+)

Do you think we need to name the devices using the label ?


No - absolutely not. If we use label to name devices then we have to validate that the string is a correctly formed device name and that it has not been previously used.

Anything that doesn't contain '/' can be a device name ? And it is very easy to find if the device name has been used in the coresight bus, after all these devices only appear there.

It is as good as :

bus_find_device_by_name(coresight_bus_type, NULL, name) == NULL

Of course with coresight_mutex() held.

Suzuki



Using the canonical driver selected names works best as we are guaranteed a unique name and the information label can be used to provide flexible context information that best matches the users requirements.

Mike

Or is this enough ?

Suzuki



diff --git a/Documentation/ABI/testing/sysfs-bus-coresight-devices-cti
b/Documentation/ABI/testing/sysfs-bus-coresight-devices-cti
index bf2869c413e7..909670e0451a 100644
--- a/Documentation/ABI/testing/sysfs-bus-coresight-devices-cti
+++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-cti
@@ -239,3 +239,9 @@ Date: March 2020
KernelVersion 5.7
Contact: Mike Leach or Mathieu Poirier
Description: (Write) Clear all channel / trigger programming.
+
+What: /sys/bus/coresight/devices/<cti-name>/label
+Date: Dec 2024
+KernelVersion 6.14
+Contact: Mao Jinlong <quic_jinlmao@xxxxxxxxxxx>
+Description: (Read) Show hardware context information of device.
diff --git
a/Documentation/ABI/testing/sysfs-bus-coresight-devices-funnel
b/Documentation/ABI/testing/sysfs-bus-coresight-devices-funnel
index d75acda5e1b3..944aad879aeb 100644
--- a/Documentation/ABI/testing/sysfs-bus-coresight-devices-funnel
+++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-funnel
@@ -10,3 +10,9 @@ Date: November 2014
KernelVersion: 3.19
Contact: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
Description: (RW) Defines input port priority order.
+
+What: /sys/bus/coresight/devices/<memory_map>.funnel/label
+Date: Dec 2024
+KernelVersion 6.14
+Contact: Mao Jinlong <quic_jinlmao@xxxxxxxxxxx>
+Description: (Read) Show hardware context information of device.
diff --git
a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
index bf710ea6e0ef..309802246398 100644
--- a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
+++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
@@ -257,3 +257,9 @@ Contact: Jinlong Mao (QUIC)
<quic_jinlmao@xxxxxxxxxxx>, Tao Zhang (QUIC) <quic_t
Description:
(RW) Set/Get the MSR(mux select register) for the CMB
subunit
TPDM.
+
+What: /sys/bus/coresight/devices/<tpdm-name>/label
+Date: Dec 2024
+KernelVersion 6.14
+Contact: Mao Jinlong <quic_jinlmao@xxxxxxxxxxx>
+Description: (Read) Show hardware context information of device.
diff --git a/drivers/hwtracing/coresight/coresight-sysfs.c
b/drivers/hwtracing/coresight/coresight-sysfs.c
index a01c9e54e2ed..4af40cd7d75a 100644
--- a/drivers/hwtracing/coresight/coresight-sysfs.c
+++ b/drivers/hwtracing/coresight/coresight-sysfs.c
@@ -7,6 +7,7 @@
#include <linux/device.h>
#include <linux/idr.h>
#include <linux/kernel.h>
+#include <linux/property.h>

#include "coresight-priv.h"
#include "coresight-trace-id.h"
@@ -366,18 +367,47 @@ static ssize_t enable_source_store(struct device
*dev,
}
static DEVICE_ATTR_RW(enable_source);

+static ssize_t label_show(struct device *dev,
+ struct device_attribute *attr, char *buf) {
+
+ const char *str;
+ int ret = 0;
+
+ ret = fwnode_property_read_string(dev_fwnode(dev), "label", &str);
+ if (ret == 0)
+ return scnprintf(buf, PAGE_SIZE, "%s\n", str);
+ else
+ return ret;
+}
+static DEVICE_ATTR_RO(label);
+
static struct attribute *coresight_sink_attrs[] = {
&dev_attr_enable_sink.attr,
+ &dev_attr_label.attr,
NULL,
};
ATTRIBUTE_GROUPS(coresight_sink);

static struct attribute *coresight_source_attrs[] = {
&dev_attr_enable_source.attr,
+ &dev_attr_label.attr,
NULL,
};
ATTRIBUTE_GROUPS(coresight_source);

+static struct attribute *coresight_link_attrs[] = {
+ &dev_attr_label.attr,
+ NULL,
+};
+ATTRIBUTE_GROUPS(coresight_link);
+
+static struct attribute *coresight_helper_attrs[] = {
+ &dev_attr_label.attr,
+ NULL,
+};
+ATTRIBUTE_GROUPS(coresight_helper);
+
const struct device_type coresight_dev_type[] = {
[CORESIGHT_DEV_TYPE_SINK] = {
.name = "sink",
@@ -385,6 +415,7 @@ const struct device_type coresight_dev_type[] = {
},
[CORESIGHT_DEV_TYPE_LINK] = {
.name = "link",
+ .groups = coresight_link_groups,
},
[CORESIGHT_DEV_TYPE_LINKSINK] = {
.name = "linksink",
@@ -396,6 +427,7 @@ const struct device_type coresight_dev_type[] = {
},
[CORESIGHT_DEV_TYPE_HELPER] = {
.name = "helper",
+ .groups = coresight_helper_groups,
}
};
/* Ensure the enum matches the names and groups */

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