On Wed, Sep 16, 2020 at 03:15:04PM -0500, Pierre-Louis Bossart wrote:
> The MIPI DisCo device properties that are read by the driver from
> platform firmware, or hard-coded in the driver, should only be
> provided as sysfs entries when a driver probes successfully.
>
> However the device status and device number is updated even when there
> is no driver present, and hence can be updated when a Slave device is
> detected on the bus without being described in platform firmware and
> without any driver registered/probed.
>
> The attr group added for Slave status and device number is not handled
> by devm_ routines to avoid errors such as "Resources present before
> probing". Since device_del() explicitly removes attribute groups, only
> an init function is provided.
>
> Credits to Vinod Koul for the status_show() function, shared in a
> separate patch and used as is here. The status table was modified to
> remove an unnecessary enum and status_show() is handled in a different
> group attribute than what was suggested by Vinod.
>
> Reviewed-by: Bard Liao <yung-chuan.liao@xxxxxxxxxxxxxxx>
> Reviewed-by: Rander Wang <rander.wang@xxxxxxxxxxxxxxx>
> Reviewed-by: Guennadi Liakhovetski <guennadi.liakhovetski@xxxxxxxxxxxxxxx>
> Tested-by: Srinivas Kandgatla <srinivas.kandagatla@xxxxxxxxxx>
> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
> ---
> .../ABI/testing/sysfs-bus-soundwire-slave | 18 ++++++
> drivers/soundwire/slave.c | 2 +
> drivers/soundwire/sysfs_local.h | 4 ++
> drivers/soundwire/sysfs_slave.c | 64 ++++++++++++++++++-
> 4 files changed, 87 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-soundwire-slave b/Documentation/ABI/testing/sysfs-bus-soundwire-slave
> index db4c9511d1aa..425adf7b8aec 100644
> --- a/Documentation/ABI/testing/sysfs-bus-soundwire-slave
> +++ b/Documentation/ABI/testing/sysfs-bus-soundwire-slave
> @@ -1,3 +1,21 @@
> +What: /sys/bus/soundwire/devices/sdw:.../dev-status/status
> + /sys/bus/soundwire/devices/sdw:.../dev-status/device_number
> +
> +Date: September 2020
> +
> +Contact: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
> + Bard Liao <yung-chuan.liao@xxxxxxxxxxxxxxx>
> + Vinod Koul <vkoul@xxxxxxxxxx>
> +
> +Description: SoundWire Slave status
> +
> + These properties report the Slave status, e.g. if it
> + is UNATTACHED or not, and in the latter case show the
> + device_number. This status information is useful to
> + detect devices exposed by platform firmware but not
> + physically present on the bus, and conversely devices
> + not exposed in platform firmware but enumerated.
> +
> What: /sys/bus/soundwire/devices/sdw:.../dev-properties/mipi_revision
> /sys/bus/soundwire/devices/sdw:.../dev-properties/wake_capable
> /sys/bus/soundwire/devices/sdw:.../dev-properties/test_mode_capable
> diff --git a/drivers/soundwire/slave.c b/drivers/soundwire/slave.c
> index 19b012310c29..ee554a215e44 100644
> --- a/drivers/soundwire/slave.c
> +++ b/drivers/soundwire/slave.c
> @@ -6,6 +6,7 @@
> #include <linux/soundwire/sdw.h>
> #include <linux/soundwire/sdw_type.h>
> #include "bus.h"
> +#include "sysfs_local.h"
>
> static void sdw_slave_release(struct device *dev)
> {
> @@ -83,6 +84,7 @@ int sdw_slave_add(struct sdw_bus *bus,
> return ret;
> }
> sdw_slave_debugfs_init(slave);
> + sdw_slave_status_sysfs_init(slave);
>
> return ret;
> }
> diff --git a/drivers/soundwire/sysfs_local.h b/drivers/soundwire/sysfs_local.h
> index ff60adee3c41..52f2eabf5b4b 100644
> --- a/drivers/soundwire/sysfs_local.h
> +++ b/drivers/soundwire/sysfs_local.h
> @@ -8,6 +8,10 @@
> * SDW sysfs APIs -
> */
>
> +/* basic routine to report status of Slave (attachment, dev_num) */
> +int sdw_slave_status_sysfs_init(struct sdw_slave *slave);
> +
> +/* additional device-managed properties reported after driver probe */
> int sdw_slave_sysfs_init(struct sdw_slave *slave);
> int sdw_slave_sysfs_dpn_init(struct sdw_slave *slave);
>
> diff --git a/drivers/soundwire/sysfs_slave.c b/drivers/soundwire/sysfs_slave.c
> index f510071b0add..36eaca343601 100644
> --- a/drivers/soundwire/sysfs_slave.c
> +++ b/drivers/soundwire/sysfs_slave.c
> @@ -16,10 +16,14 @@
>
> /*
> * The sysfs for Slave reflects the MIPI description as given
> - * in the MIPI DisCo spec
> + * in the MIPI DisCo spec. dev-status properties come directly
> + * from the MIPI SoundWire specification.
> *
> * Base file is device
> * |---- modalias
> + * |---- dev-status
> + * |---- status
> + * |---- device_number
> * |---- dev-properties
> * |---- mipi_revision
> * |---- wake_capable
> @@ -212,3 +216,61 @@ int sdw_slave_sysfs_init(struct sdw_slave *slave)
>
> return 0;
> }
> +
> +/*
> + * the status is shown in capital letters for UNATTACHED and RESERVED
> + * on purpose, to alert users to the fact that these status values are
> + * not expected.
> + */
> +static const char *const slave_status[] = {
> + [SDW_SLAVE_UNATTACHED] = "UNATTACHED",
> + [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 ssize_t device_number_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct sdw_slave *slave = dev_to_sdw_dev(dev);
> +
> + if (slave->status == SDW_SLAVE_UNATTACHED)
> + return sprintf(buf, "%s", "N/A");
> + else
> + return sprintf(buf, "%d", slave->dev_num);
> +}
> +static DEVICE_ATTR_RO(device_number);
> +
> +static struct attribute *slave_status_attrs[] = {
> + &dev_attr_status.attr,
> + &dev_attr_device_number.attr,
> + NULL,
> +};
> +
> +/*
> + * we don't use ATTRIBUTES_GROUP here since we want to add a subdirectory
> + * for device-status
> + */
> +static struct attribute_group sdw_slave_status_attr_group = {
> + .attrs = slave_status_attrs,
> + .name = "dev-status",
> +};
> +
> +/*
> + * We can't use devm_ here, otherwise resources would be added before
> + * the driver probe. The group is removed in device_del() however.
> + */
> +
> +int sdw_slave_status_sysfs_init(struct sdw_slave *slave)
> +{
> + return device_add_group(&slave->dev, &sdw_slave_status_attr_group);
DOesn't this race with userspace? Why not make this part of the default
set of device attributes and have the driver core create them
automatically?
thanks,
greg k-h
