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

From: Pierre-Louis Bossart
Date: Thu Sep 10 2020 - 17:28:59 EST

May be we could make the enumerated devices discovery bit more verbose!

Maybe adding a device number sysfs entry would help, e.g. reporting
NotAttched or a value in [0,11] would tell you if the device is actually

Agreed, I cooked this patch to report verbose device status, let me know
if you are okay with this. I think this would be useful regardless of
current discussion.

On Db845c I see:

root@linaro-alip:/sys/bus/soundwire/devices# cat sdw:0:217:2010:0:1/status
root@linaro-alip:/sys/bus/soundwire/devices# cat sdw:0:217:2010:0:2/status

looks like we are all aligned on the idea, I have a similar patch to at

The difference is that the sysfs status and device_number is added even without a driver probe and when there's no firmware description. sysfs is currently only added after the driver probe, which wouldn't work for the case Srinivas was trying to deal with.

but the way you dealt the status below is better than the switch case I used, so will merge this into my code.

Srinivas' patch needs a fix for ACPI platforms, won't probe otherwise since we don't have an of_node. If that's alright with everyone I can submit a patchset that gathers the 3 contributions.

diff --git a/drivers/soundwire/sysfs_slave.c b/drivers/soundwire/sysfs_slave.c
index f510071b0add..3b2765f10024 100644
--- a/drivers/soundwire/sysfs_slave.c
+++ b/drivers/soundwire/sysfs_slave.c
@@ -97,8 +97,27 @@ static ssize_t modalias_show(struct device *dev,
static DEVICE_ATTR_RO(modalias);
+static const char *const slave_status[SDW_SLAVE_MAX] = {
+ [SDW_SLAVE_ATTACHED] = "Attached",
+ [SDW_SLAVE_ALERT] = "Alert",
+ [SDW_SLAVE_RESERVED] = "Reserved",
+static ssize_t status_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+ struct sdw_slave *slave = dev_to_sdw_dev(dev);
+ return sprintf(buf, "%s\n", slave_status[slave->status]);
+static DEVICE_ATTR_RO(status);
static struct attribute *slave_attrs[] = {
+ &dev_attr_status.attr,