Re: [PATCH] soundwire: bus: add enumerated slave to device list

From: Srinivas Kandagatla
Date: Wed Sep 09 2020 - 12:11:17 EST

On 09/09/2020 14:37, Pierre-Louis Bossart wrote:

On 9/9/20 3:27 AM, Srinivas Kandagatla wrote:
Currently slave devices are only added either from device tree or acpi
entries. However lets say, there is wrong or no entry of a slave device
in DT that is enumerated, then there is no way for user to know all
the enumerated devices on the bus.

Sorry Srinivas, I don't understand your point.

The sysfs entries will include all devices that are described in platform firmware (be it DT or ACPI).

yes that is true, but it will not include all the enumerated devices on the bus!

In my case on a new board I was trying to figure out what devices are on the bus even before even adding any device tree entries!

In second case I had a typo in the device tree entry and sysfs displayed devices with that typo rather than actual enumerated device id.

If you add to sysfs entries unknown devices which happen to be present on the bus, then what? How would you identify them from the devices that are described in firmware?

Both of them should be displayed in sysfs, core should be able to differentiate this based on the presence of fw_node or of_node and not bind!

Also the sysfs entries describe properties, but if you haven't bound a driver then how would this work?

This is would be informative, atleast in cases like me!

All I want to know is the list of enumerated devices on the bus, If doing this way is not the right thing, then am happy to try any suggestion!

For now I have managed to figure out enumerated device ids on the bus with this patch, I was hoping that other people would also hit such issue, so I sent this patch!


I really feel this deserves more explanations on the problem statement and what you are hoping to achieve in this case.


To fix this add slave device by default if there is no matching dt or
acpi entry, so that we can see this in sysfs entry.

In my case I had a wrong address entry in DT, However I had no way to
know what devices are actually enumerated on the bus!

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>
  drivers/soundwire/bus.c      | 1 +
  drivers/soundwire/bus.h      | 2 ++
  drivers/soundwire/bus_type.c | 6 ++++++
  drivers/soundwire/slave.c    | 4 ++--
  4 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index e6e0fb9a81b4..55d9c22c4ec5 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -699,6 +699,7 @@ static int sdw_program_device_num(struct sdw_bus *bus)
          if (!found) {
              /* TODO: Park this device in Group 13 */
+            sdw_slave_add(bus, &id, NULL);
              dev_err(bus->dev, "Slave Entry not found\n");
diff --git a/drivers/soundwire/bus.h b/drivers/soundwire/bus.h
index 82484f741168..1517d6789dff 100644
--- a/drivers/soundwire/bus.h
+++ b/drivers/soundwire/bus.h
@@ -19,6 +19,8 @@ static inline int sdw_acpi_find_slaves(struct sdw_bus *bus)
  int sdw_of_find_slaves(struct sdw_bus *bus);
  void sdw_extract_slave_id(struct sdw_bus *bus,
                u64 addr, struct sdw_slave_id *id);
+int sdw_slave_add(struct sdw_bus *bus, struct sdw_slave_id *id,
+          struct fwnode_handle *fwnode);
  int sdw_master_device_add(struct sdw_bus *bus, struct device *parent,
                struct fwnode_handle *fwnode);
  int sdw_master_device_del(struct sdw_bus *bus);
diff --git a/drivers/soundwire/bus_type.c b/drivers/soundwire/bus_type.c
index 6fba55898cf0..ac036223046f 100644
--- a/drivers/soundwire/bus_type.c
+++ b/drivers/soundwire/bus_type.c
@@ -84,6 +84,12 @@ static int sdw_drv_probe(struct device *dev)
      const struct sdw_device_id *id;
      int ret;
+    /*
+     * fw description is mandatory to bind
+     */
+    if (!dev->fwnode || !dev->of_node)
+        return -ENODEV;
      id = sdw_get_device_id(slave, drv);
      if (!id)
          return -ENODEV;
diff --git a/drivers/soundwire/slave.c b/drivers/soundwire/slave.c
index 0839445ee07b..24a16ebf9ae2 100644
--- a/drivers/soundwire/slave.c
+++ b/drivers/soundwire/slave.c
@@ -20,8 +20,8 @@ struct device_type sdw_slave_type = {
      .uevent =    sdw_slave_uevent,
-static int sdw_slave_add(struct sdw_bus *bus,
-             struct sdw_slave_id *id, struct fwnode_handle *fwnode)
+int sdw_slave_add(struct sdw_bus *bus,
+          struct sdw_slave_id *id, struct fwnode_handle *fwnode)
      struct sdw_slave *slave;
      int ret;