Re: [PATCH v6 09/13] Add nodes for dsb edge control

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On 20/06/2023 09:31, Tao Zhang wrote:

On 6/20/2023 3:37 PM, Greg Kroah-Hartman wrote:
On Tue, Jun 20, 2023 at 03:32:37PM +0800, Tao Zhang wrote:
Add the nodes to set value for DSB edge control and DSB edge
control mask. Each DSB subunit TPDM has maximum of n(n<16) EDCR
resgisters to configure edge control. DSB edge detection control
00: Rising edge detection
01: Falling edge detection
10: Rising and falling edge detection (toggle detection)
And each DSB subunit TPDM has maximum of m(m<8) ECDMR registers to
configure mask. Eight 32 bit registers providing DSB interface
edge detection mask control.

Signed-off-by: Tao Zhang <quic_taozha@xxxxxxxxxxx>
---
  .../ABI/testing/sysfs-bus-coresight-devices-tpdm   |  32 +++++
  drivers/hwtracing/coresight/coresight-tpdm.c       | 143 ++++++++++++++++++++-
  drivers/hwtracing/coresight/coresight-tpdm.h       |  22 ++++
  3 files changed, 196 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
index 2a82cd0..34189e4a 100644
--- a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
+++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
@@ -60,3 +60,35 @@ Description:
          Bit[3] : Set to 0 for low performance mode.
                   Set to 1 for high performance mode.
          Bit[4:8] : Select byte lane for high performance mode.
+
+What:        /sys/bus/coresight/devices/<tpdm-name>/dsb_edge_ctrl
+Date:        March 2023
+KernelVersion    6.5
+Contact:    Jinlong Mao (QUIC) <quic_jinlmao@xxxxxxxxxxx>, Tao Zhang (QUIC) <quic_taozha@xxxxxxxxxxx>
+Description:
+        Read/Write a set of the edge control registers of the DSB
+        in TPDM.
+
+        Expected format is the following:
+        <integer1> <integer2> <integer3>
sysfs is "one value", not 3.  Please never have to parse a sysfs file.

Do you mean sysfs file can only accept "one value"?

I see that more than one value are written to the sysfs file "trigout_attach".


+static ssize_t dsb_edge_ctrl_show(struct device *dev,
+                       struct device_attribute *attr,
+                       char *buf)
+{
+    struct tpdm_drvdata *drvdata = dev_get_drvdata(dev->parent);
+    ssize_t size = 0;
+    unsigned long bytes;
+    int i;
+
+    spin_lock(&drvdata->spinlock);
+    for (i = 0; i < TPDM_DSB_MAX_EDCR; i++) {
+        bytes = sysfs_emit_at(buf, size,
+                  "Index:0x%x Val:0x%x\n", i,
Again, no, one value, no "string" needed to parse anything.

I also see other sysfs files can be read more than one value in other drivers.

Is this "one value" limitation the usage rule of Linux sysfs system?

Or am I misunderstanding what you mean?

Please fix the other sysfs tunables in the following patches.

Kind regards
Suzuki





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