Expose model and fw_version via sysfs. Also query the model
in probe to make sure, that the I2C communication with the
device works before successfully probing the driver.
This is a bit complicated, since EETI devices do not have
a sync interface. Sending the commands and directly reading
does not work. Sending the command and waiting for some time
is also not an option, since there might be touch events in
the mean time.
Last but not least we do not cache the results, since this
interface can be used to check the I2C communication is still
working as expected.
Signed-off-by: Sebastian Reichel <[email protected]>
---
.../ABI/testing/sysfs-driver-input-exc3000 | 15 ++
drivers/input/touchscreen/exc3000.c | 145 +++++++++++++++++-
2 files changed, 159 insertions(+), 1 deletion(-)
create mode 100644 Documentation/ABI/testing/sysfs-driver-input-exc3000
diff --git a/Documentation/ABI/testing/sysfs-driver-input-exc3000 b/Documentation/ABI/testing/sysfs-driver-input-exc3000
new file mode 100644
index 000000000000..d79da4f869af
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-input-exc3000
@@ -0,0 +1,15 @@
+What: /sys/class/input/inputX/fw_version
+Date: May 2020
+Contact: [email protected]
+Description: Reports the firmware version provided by the touchscreen, for example "00_T6" on a EXC80H60
+
+ Access: Read
+ Valid values: Represented as string
+
+What: /sys/class/input/inputX/model
+Date: May 2020
+Contact: [email protected]
+Description: Reports the model identification provided by the touchscreen, for example "Orion_1320" on a EXC80H60
+
+ Access: Read
+ Valid values: Represented as string
diff --git a/drivers/input/touchscreen/exc3000.c b/drivers/input/touchscreen/exc3000.c
index b497bd2ae41d..b5a3bbb63504 100644
--- a/drivers/input/touchscreen/exc3000.c
+++ b/drivers/input/touchscreen/exc3000.c
@@ -25,6 +25,9 @@
#define EXC3000_LEN_FRAME 66
#define EXC3000_LEN_POINT 10
+#define EXC3000_LEN_MODEL_NAME 16
+#define EXC3000_LEN_FW_VERSION 16
+
#define EXC3000_MT1_EVENT 0x06
#define EXC3000_MT2_EVENT 0x18
@@ -65,6 +68,11 @@ struct exc3000_data {
struct touchscreen_properties prop;
struct timer_list timer;
u8 buf[2 * EXC3000_LEN_FRAME];
+ struct completion wait_event;
+ struct mutex query_lock;
+ int query_result;
+ char model[EXC3000_LEN_MODEL_NAME];
+ char fw_version[EXC3000_LEN_FW_VERSION];
};
static void exc3000_report_slots(struct input_dev *input,
@@ -150,6 +158,28 @@ static int exc3000_read_data(struct exc3000_data *data,
return 0;
}
+static int exc3000_query_interrupt(struct exc3000_data *data)
+{
+ u8 *buf = data->buf;
+ int err;
+
+ err = i2c_master_recv(data->client, buf, EXC3000_LEN_FRAME);
+ if (err < 0)
+ return err;
+
+ if (buf[0] != 0x42)
+ return -EPROTO;
+
+ if (buf[4] == 'E')
+ strlcpy(data->model, buf+5, sizeof(data->model));
+ else if (buf[4] == 'D')
+ strlcpy(data->fw_version, buf+5, sizeof(data->fw_version));
+ else
+ return -EPROTO;
+
+ return 0;
+}
+
static irqreturn_t exc3000_interrupt(int irq, void *dev_id)
{
struct exc3000_data *data = dev_id;
@@ -158,6 +188,12 @@ static irqreturn_t exc3000_interrupt(int irq, void *dev_id)
int slots, total_slots;
int error;
+ if (mutex_is_locked(&data->query_lock)) {
+ data->query_result = exc3000_query_interrupt(data);
+ complete(&data->wait_event);
+ goto out;
+ }
+
error = exc3000_read_data(data, buf, &total_slots);
if (error) {
/* Schedule a timer to release "stuck" contacts */
@@ -185,11 +221,94 @@ static irqreturn_t exc3000_interrupt(int irq, void *dev_id)
return IRQ_HANDLED;
}
+static ssize_t fw_version_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct exc3000_data *data = dev_get_drvdata(dev);
+ static const u8 request[68] = {
+ 0x67, 0x00, 0x42, 0x00, 0x03, 0x01, 'D', 0x00
+ };
+ struct i2c_client *client = data->client;
+ int err;
+
+ mutex_lock(&data->query_lock);
+
+ data->query_result = -ETIMEDOUT;
+ reinit_completion(&data->wait_event);
+
+ err = i2c_master_send(client, request, sizeof(request));
+ if (err < 0) {
+ mutex_unlock(&data->query_lock);
+ return err;
+ }
+
+ wait_for_completion_interruptible_timeout(&data->wait_event, 1*HZ);
+ mutex_unlock(&data->query_lock);
+
+ if (data->query_result < 0)
+ return data->query_result;
+
+ return sprintf(buf, "%s\n", data->fw_version);
+}
+static DEVICE_ATTR_RO(fw_version);
+
+static ssize_t exc3000_get_model(struct exc3000_data *data)
+{
+ static const u8 request[68] = {
+ 0x67, 0x00, 0x42, 0x00, 0x03, 0x01, 'E', 0x00
+ };
+ struct i2c_client *client = data->client;
+ int err;
+
+ mutex_lock(&data->query_lock);
+ data->query_result = -ETIMEDOUT;
+ reinit_completion(&data->wait_event);
+
+ err = i2c_master_send(client, request, sizeof(request));
+ if (err < 0) {
+ mutex_unlock(&data->query_lock);
+ return err;
+ }
+
+ wait_for_completion_interruptible_timeout(&data->wait_event, 1 * HZ);
+ mutex_unlock(&data->query_lock);
+
+ return data->query_result;
+}
+
+static ssize_t model_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct exc3000_data *data = dev_get_drvdata(dev);
+ int err = exc3000_get_model(data);
+
+ if (err < 0)
+ return err;
+
+ return sprintf(buf, "%s\n", data->model);
+}
+static DEVICE_ATTR_RO(model);
+
+static struct attribute *sysfs_attrs[] = {
+ &dev_attr_fw_version.attr,
+ &dev_attr_model.attr,
+ NULL
+};
+
+static struct attribute_group exc3000_attribute_group = {
+ .attrs = sysfs_attrs
+};
+
+static const struct attribute_group *exc3000_attribute_groups[] = {
+ &exc3000_attribute_group,
+ NULL
+};
+
static int exc3000_probe(struct i2c_client *client)
{
struct exc3000_data *data;
struct input_dev *input;
- int error, max_xy;
+ int error, max_xy, retry;
data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
if (!data)
@@ -203,15 +322,19 @@ static int exc3000_probe(struct i2c_client *client)
data->info = &exc3000_info[eeti_dev_id];
}
timer_setup(&data->timer, exc3000_timer, 0);
+ init_completion(&data->wait_event);
+ mutex_init(&data->query_lock);
input = devm_input_allocate_device(&client->dev);
if (!input)
return -ENOMEM;
data->input = input;
+ input_set_drvdata(input, data);
input->name = data->info->name;
input->id.bustype = BUS_I2C;
+ input->dev.groups = exc3000_attribute_groups;
max_xy = data->info->max_xy;
input_set_abs_params(input, ABS_MT_POSITION_X, 0, max_xy, 0, 0);
@@ -234,6 +357,26 @@ static int exc3000_probe(struct i2c_client *client)
if (error)
return error;
+ /*
+ * I²C does not have built-in recovery, so retry on failure. This ensures,
+ * that the device probe will not fail for temporary issues on the bus.
+ * This is not needed for the sysfs calls (userspace will receive the error
+ * code and can start another query) and cannot be done for touch events
+ * (but that only means loosing one or two touch events anyways).
+ */
+ for (retry = 0; retry < 3; ++retry) {
+ error = exc3000_get_model(data);
+ if (!error)
+ break;
+ dev_warn(&client->dev, "Retry %d get EETI EXC3000 model: %d\n",
+ retry + 1, error);
+ }
+
+ if (error)
+ return error;
+
+ dev_dbg(&client->dev, "TS Model: %s", data->model);
+
return 0;
}
--
2.26.2
Hi Sebastian,
On 20/5/20 17:39, Sebastian Reichel wrote:
> Expose model and fw_version via sysfs. Also query the model
> in probe to make sure, that the I2C communication with the
> device works before successfully probing the driver.
>
> This is a bit complicated, since EETI devices do not have
> a sync interface. Sending the commands and directly reading
> does not work. Sending the command and waiting for some time
> is also not an option, since there might be touch events in
> the mean time.
>
> Last but not least we do not cache the results, since this
> interface can be used to check the I2C communication is still
> working as expected.
>
> Signed-off-by: Sebastian Reichel <[email protected]>
I went through the code and understood the reasoning to implement that way, if
it helps:
Reviewed-by: Enric Balletbo i Serra <[email protected]>
> ---
> .../ABI/testing/sysfs-driver-input-exc3000 | 15 ++
> drivers/input/touchscreen/exc3000.c | 145 +++++++++++++++++-
> 2 files changed, 159 insertions(+), 1 deletion(-)
> create mode 100644 Documentation/ABI/testing/sysfs-driver-input-exc3000
>
> diff --git a/Documentation/ABI/testing/sysfs-driver-input-exc3000 b/Documentation/ABI/testing/sysfs-driver-input-exc3000
> new file mode 100644
> index 000000000000..d79da4f869af
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-driver-input-exc3000
> @@ -0,0 +1,15 @@
> +What: /sys/class/input/inputX/fw_version
> +Date: May 2020
> +Contact: [email protected]
> +Description: Reports the firmware version provided by the touchscreen, for example "00_T6" on a EXC80H60
> +
> + Access: Read
> + Valid values: Represented as string
> +
> +What: /sys/class/input/inputX/model
> +Date: May 2020
> +Contact: [email protected]
> +Description: Reports the model identification provided by the touchscreen, for example "Orion_1320" on a EXC80H60
> +
> + Access: Read
> + Valid values: Represented as string
> diff --git a/drivers/input/touchscreen/exc3000.c b/drivers/input/touchscreen/exc3000.c
> index b497bd2ae41d..b5a3bbb63504 100644
> --- a/drivers/input/touchscreen/exc3000.c
> +++ b/drivers/input/touchscreen/exc3000.c
> @@ -25,6 +25,9 @@
> #define EXC3000_LEN_FRAME 66
> #define EXC3000_LEN_POINT 10
>
> +#define EXC3000_LEN_MODEL_NAME 16
> +#define EXC3000_LEN_FW_VERSION 16
> +
> #define EXC3000_MT1_EVENT 0x06
> #define EXC3000_MT2_EVENT 0x18
>
> @@ -65,6 +68,11 @@ struct exc3000_data {
> struct touchscreen_properties prop;
> struct timer_list timer;
> u8 buf[2 * EXC3000_LEN_FRAME];
> + struct completion wait_event;
> + struct mutex query_lock;
> + int query_result;
> + char model[EXC3000_LEN_MODEL_NAME];
> + char fw_version[EXC3000_LEN_FW_VERSION];
> };
>
> static void exc3000_report_slots(struct input_dev *input,
> @@ -150,6 +158,28 @@ static int exc3000_read_data(struct exc3000_data *data,
> return 0;
> }
>
> +static int exc3000_query_interrupt(struct exc3000_data *data)
> +{
> + u8 *buf = data->buf;
> + int err;
> +
> + err = i2c_master_recv(data->client, buf, EXC3000_LEN_FRAME);
> + if (err < 0)
> + return err;
> +
> + if (buf[0] != 0x42)
> + return -EPROTO;
> +
> + if (buf[4] == 'E')
> + strlcpy(data->model, buf+5, sizeof(data->model));
> + else if (buf[4] == 'D')
> + strlcpy(data->fw_version, buf+5, sizeof(data->fw_version));
> + else
> + return -EPROTO;
> +
> + return 0;
> +}
> +
> static irqreturn_t exc3000_interrupt(int irq, void *dev_id)
> {
> struct exc3000_data *data = dev_id;
> @@ -158,6 +188,12 @@ static irqreturn_t exc3000_interrupt(int irq, void *dev_id)
> int slots, total_slots;
> int error;
>
> + if (mutex_is_locked(&data->query_lock)) {
> + data->query_result = exc3000_query_interrupt(data);
> + complete(&data->wait_event);
> + goto out;
> + }
> +
> error = exc3000_read_data(data, buf, &total_slots);
> if (error) {
> /* Schedule a timer to release "stuck" contacts */
> @@ -185,11 +221,94 @@ static irqreturn_t exc3000_interrupt(int irq, void *dev_id)
> return IRQ_HANDLED;
> }
>
> +static ssize_t fw_version_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct exc3000_data *data = dev_get_drvdata(dev);
> + static const u8 request[68] = {
> + 0x67, 0x00, 0x42, 0x00, 0x03, 0x01, 'D', 0x00
> + };
> + struct i2c_client *client = data->client;
> + int err;
> +
> + mutex_lock(&data->query_lock);
> +
> + data->query_result = -ETIMEDOUT;
> + reinit_completion(&data->wait_event);
> +
> + err = i2c_master_send(client, request, sizeof(request));
> + if (err < 0) {
> + mutex_unlock(&data->query_lock);
> + return err;
> + }
> +
> + wait_for_completion_interruptible_timeout(&data->wait_event, 1*HZ);
> + mutex_unlock(&data->query_lock);
> +
> + if (data->query_result < 0)
> + return data->query_result;
> +
> + return sprintf(buf, "%s\n", data->fw_version);
> +}
> +static DEVICE_ATTR_RO(fw_version);
> +
> +static ssize_t exc3000_get_model(struct exc3000_data *data)
> +{
> + static const u8 request[68] = {
> + 0x67, 0x00, 0x42, 0x00, 0x03, 0x01, 'E', 0x00
> + };
> + struct i2c_client *client = data->client;
> + int err;
> +
> + mutex_lock(&data->query_lock);
> + data->query_result = -ETIMEDOUT;
> + reinit_completion(&data->wait_event);
> +
> + err = i2c_master_send(client, request, sizeof(request));
> + if (err < 0) {
> + mutex_unlock(&data->query_lock);
> + return err;
> + }
> +
> + wait_for_completion_interruptible_timeout(&data->wait_event, 1 * HZ);
> + mutex_unlock(&data->query_lock);
> +
> + return data->query_result;
> +}
> +
> +static ssize_t model_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct exc3000_data *data = dev_get_drvdata(dev);
> + int err = exc3000_get_model(data);
> +
> + if (err < 0)
> + return err;
> +
> + return sprintf(buf, "%s\n", data->model);
> +}
> +static DEVICE_ATTR_RO(model);
> +
> +static struct attribute *sysfs_attrs[] = {
> + &dev_attr_fw_version.attr,
> + &dev_attr_model.attr,
> + NULL
> +};
> +
> +static struct attribute_group exc3000_attribute_group = {
> + .attrs = sysfs_attrs
> +};
> +
> +static const struct attribute_group *exc3000_attribute_groups[] = {
> + &exc3000_attribute_group,
> + NULL
> +};
> +
> static int exc3000_probe(struct i2c_client *client)
> {
> struct exc3000_data *data;
> struct input_dev *input;
> - int error, max_xy;
> + int error, max_xy, retry;
>
> data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
> if (!data)
> @@ -203,15 +322,19 @@ static int exc3000_probe(struct i2c_client *client)
> data->info = &exc3000_info[eeti_dev_id];
> }
> timer_setup(&data->timer, exc3000_timer, 0);
> + init_completion(&data->wait_event);
> + mutex_init(&data->query_lock);
>
> input = devm_input_allocate_device(&client->dev);
> if (!input)
> return -ENOMEM;
>
> data->input = input;
> + input_set_drvdata(input, data);
>
> input->name = data->info->name;
> input->id.bustype = BUS_I2C;
> + input->dev.groups = exc3000_attribute_groups;
>
> max_xy = data->info->max_xy;
> input_set_abs_params(input, ABS_MT_POSITION_X, 0, max_xy, 0, 0);
> @@ -234,6 +357,26 @@ static int exc3000_probe(struct i2c_client *client)
> if (error)
> return error;
>
> + /*
> + * I²C does not have built-in recovery, so retry on failure. This ensures,
> + * that the device probe will not fail for temporary issues on the bus.
> + * This is not needed for the sysfs calls (userspace will receive the error
> + * code and can start another query) and cannot be done for touch events
> + * (but that only means loosing one or two touch events anyways).
> + */
> + for (retry = 0; retry < 3; ++retry) {
> + error = exc3000_get_model(data);
> + if (!error)
> + break;
> + dev_warn(&client->dev, "Retry %d get EETI EXC3000 model: %d\n",
> + retry + 1, error);
> + }
> +
> + if (error)
> + return error;
> +
> + dev_dbg(&client->dev, "TS Model: %s", data->model);
> +
> return 0;
> }
>
>
Hi Sebastian,
On Wed, May 20, 2020 at 05:39:35PM +0200, Sebastian Reichel wrote:
> Expose model and fw_version via sysfs. Also query the model
> in probe to make sure, that the I2C communication with the
> device works before successfully probing the driver.
>
> This is a bit complicated, since EETI devices do not have
> a sync interface. Sending the commands and directly reading
> does not work. Sending the command and waiting for some time
> is also not an option, since there might be touch events in
> the mean time.
>
> Last but not least we do not cache the results, since this
> interface can be used to check the I2C communication is still
> working as expected.
>
> Signed-off-by: Sebastian Reichel <[email protected]>
> ---
> .../ABI/testing/sysfs-driver-input-exc3000 | 15 ++
> drivers/input/touchscreen/exc3000.c | 145 +++++++++++++++++-
> 2 files changed, 159 insertions(+), 1 deletion(-)
> create mode 100644 Documentation/ABI/testing/sysfs-driver-input-exc3000
>
> diff --git a/Documentation/ABI/testing/sysfs-driver-input-exc3000 b/Documentation/ABI/testing/sysfs-driver-input-exc3000
> new file mode 100644
> index 000000000000..d79da4f869af
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-driver-input-exc3000
> @@ -0,0 +1,15 @@
> +What: /sys/class/input/inputX/fw_version
> +Date: May 2020
> +Contact: [email protected]
> +Description: Reports the firmware version provided by the touchscreen, for example "00_T6" on a EXC80H60
> +
> + Access: Read
> + Valid values: Represented as string
> +
> +What: /sys/class/input/inputX/model
> +Date: May 2020
> +Contact: [email protected]
> +Description: Reports the model identification provided by the touchscreen, for example "Orion_1320" on a EXC80H60
> +
> + Access: Read
> + Valid values: Represented as string
These are properties of the controller (i2c device), not input
abstraction class on top of it, so the attributes should be attached to
i2c_client instance.
Please use devm_device_add_group() in probe to instantiate them at the
proper level.
Thanks.
--
Dmitry
Hi,
On Wed, May 20, 2020 at 10:49:52AM -0700, Dmitry Torokhov wrote:
> Hi Sebastian,
>
> On Wed, May 20, 2020 at 05:39:35PM +0200, Sebastian Reichel wrote:
> > Expose model and fw_version via sysfs. Also query the model
> > in probe to make sure, that the I2C communication with the
> > device works before successfully probing the driver.
> >
> > This is a bit complicated, since EETI devices do not have
> > a sync interface. Sending the commands and directly reading
> > does not work. Sending the command and waiting for some time
> > is also not an option, since there might be touch events in
> > the mean time.
> >
> > Last but not least we do not cache the results, since this
> > interface can be used to check the I2C communication is still
> > working as expected.
> >
> > Signed-off-by: Sebastian Reichel <[email protected]>
> > ---
> > .../ABI/testing/sysfs-driver-input-exc3000 | 15 ++
> > drivers/input/touchscreen/exc3000.c | 145 +++++++++++++++++-
> > 2 files changed, 159 insertions(+), 1 deletion(-)
> > create mode 100644 Documentation/ABI/testing/sysfs-driver-input-exc3000
> >
> > diff --git a/Documentation/ABI/testing/sysfs-driver-input-exc3000 b/Documentation/ABI/testing/sysfs-driver-input-exc3000
> > new file mode 100644
> > index 000000000000..d79da4f869af
> > --- /dev/null
> > +++ b/Documentation/ABI/testing/sysfs-driver-input-exc3000
> > @@ -0,0 +1,15 @@
> > +What: /sys/class/input/inputX/fw_version
> > +Date: May 2020
> > +Contact: [email protected]
> > +Description: Reports the firmware version provided by the touchscreen, for example "00_T6" on a EXC80H60
> > +
> > + Access: Read
> > + Valid values: Represented as string
> > +
> > +What: /sys/class/input/inputX/model
> > +Date: May 2020
> > +Contact: [email protected]
> > +Description: Reports the model identification provided by the touchscreen, for example "Orion_1320" on a EXC80H60
> > +
> > + Access: Read
> > + Valid values: Represented as string
>
> These are properties of the controller (i2c device), not input
> abstraction class on top of it, so the attributes should be attached to
> i2c_client instance.
>
> Please use devm_device_add_group() in probe to instantiate them at the
> proper level.
As written in the cover letter using devm_device_add_group() in
probe routine results in a udev race condition:
http://kroah.com/log/blog/2013/06/26/how-to-create-a-sysfs-file-correctly/
-- Sebastian
On Wed, May 20, 2020 at 11:25:40PM +0200, Sebastian Reichel wrote:
> Hi,
>
> On Wed, May 20, 2020 at 10:49:52AM -0700, Dmitry Torokhov wrote:
> > Hi Sebastian,
> >
> > On Wed, May 20, 2020 at 05:39:35PM +0200, Sebastian Reichel wrote:
> > > Expose model and fw_version via sysfs. Also query the model
> > > in probe to make sure, that the I2C communication with the
> > > device works before successfully probing the driver.
> > >
> > > This is a bit complicated, since EETI devices do not have
> > > a sync interface. Sending the commands and directly reading
> > > does not work. Sending the command and waiting for some time
> > > is also not an option, since there might be touch events in
> > > the mean time.
> > >
> > > Last but not least we do not cache the results, since this
> > > interface can be used to check the I2C communication is still
> > > working as expected.
> > >
> > > Signed-off-by: Sebastian Reichel <[email protected]>
> > > ---
> > > .../ABI/testing/sysfs-driver-input-exc3000 | 15 ++
> > > drivers/input/touchscreen/exc3000.c | 145 +++++++++++++++++-
> > > 2 files changed, 159 insertions(+), 1 deletion(-)
> > > create mode 100644 Documentation/ABI/testing/sysfs-driver-input-exc3000
> > >
> > > diff --git a/Documentation/ABI/testing/sysfs-driver-input-exc3000 b/Documentation/ABI/testing/sysfs-driver-input-exc3000
> > > new file mode 100644
> > > index 000000000000..d79da4f869af
> > > --- /dev/null
> > > +++ b/Documentation/ABI/testing/sysfs-driver-input-exc3000
> > > @@ -0,0 +1,15 @@
> > > +What: /sys/class/input/inputX/fw_version
> > > +Date: May 2020
> > > +Contact: [email protected]
> > > +Description: Reports the firmware version provided by the touchscreen, for example "00_T6" on a EXC80H60
> > > +
> > > + Access: Read
> > > + Valid values: Represented as string
> > > +
> > > +What: /sys/class/input/inputX/model
> > > +Date: May 2020
> > > +Contact: [email protected]
> > > +Description: Reports the model identification provided by the touchscreen, for example "Orion_1320" on a EXC80H60
> > > +
> > > + Access: Read
> > > + Valid values: Represented as string
> >
> > These are properties of the controller (i2c device), not input
> > abstraction class on top of it, so the attributes should be attached to
> > i2c_client instance.
> >
> > Please use devm_device_add_group() in probe to instantiate them at the
> > proper level.
>
> As written in the cover letter using devm_device_add_group() in
> probe routine results in a udev race condition:
>
> http://kroah.com/log/blog/2013/06/26/how-to-create-a-sysfs-file-correctly/
This race has been solved with the addition of KOBJ_BIND/KOBJ_UNBIND
uevents that signal when driver is bound or unbound from the device.
Granted, current systemd/udev drops them as it does not know how to
"add" to the device state, but this is on systemd to solve.
Thanks.
--
Dmitry