Some drivers that use non-standard HID features require raw output reports
sent to the device. We now forward these requests directly to user-space
so the transport-level driver can correctly send it to the device or
handle it correspondingly.

There is no way to signal back whether the transmission was successful,
moreover, there might be lots of messages coming out from the driver
flushing the output-queue. However, there is currently no driver that
causes this so we are safe. If some drivers need to transmit lots of data
this way, we need a method to synchronize this and can implement another
UHID_OUTPUT_SYNC event.
Signed-off-by: NDavid Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

If the hid-driver wants to send standardized data to the device it uses a
linux input_event. We forward this to the user-space transport-level
driver so they can perform the requested action on the device.
Signed-off-by: NDavid Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

HID core notifies us with *_open/*_close callbacks when there is an actual
user of our device. We forward these to user-space so they can react on
this. This allows user-space to skip I/O unless they receive an OPEN
event. When they receive a CLOSE event they can stop I/O again to save
energy.
Signed-off-by: NDavid Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

We send UHID_START and UHID_STOP events to user-space when the HID core
starts/stops the device. This notifies user-space about driver readiness
and data-I/O can start now.

This directly forwards the callbacks from hid-core to user-space.
Signed-off-by: NDavid Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

When the uhid_hid_parse callback is called we simply forward it to
hid_parse_report() with the data that we got in the UHID_CREATE event.
Signed-off-by: NDavid Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

This adds a new event type UHID_INPUT which allows user-space to feed raw
HID reports into the HID subsystem. We copy the data into kernel memory
and directly feed it into the HID core.

There is no error handling of the events couldn't be parsed so user-space
should consider all events successfull unless read() returns an error.
Signed-off-by: NDavid Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

UHID_CREATE and UHID_DESTROY are used to create and destroy a device on an
open uhid char-device. Internally, we allocate and register an HID device
with the HID core and immediately start the device. From now on events may
be received or sent to the device.

The UHID_CREATE event has a payload similar to the data used by
Bluetooth-HIDP when creating a new connection.
Signed-off-by: NDavid Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

Similar to read() you can only write() a single event with one call to an
uhid device. To write multiple events use writev() which is supported by
uhid.

We currently always return -EOPNOTSUPP but other events will be added in
later patches.
Signed-off-by: NDavid Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

User-space can use read() to get a single event from uhid devices. read()
does never return multiple events. This allows us to extend the event
structure and still keep backwards compatibility.

If user-space wants to get multiple events in one syscall, they should use
the readv()/writev() syscalls which are supported by uhid.

This introduces a new lock which helps us synchronizing simultaneous reads
from user-space. We also correctly return -EINVAL/-EFAULT only on errors
and retry the read() when some other thread captured the event faster than
we did.
Signed-off-by: NDavid Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

As long as the internal buffer is not empty, we return POLLIN to
user-space.

uhid->head and uhid->tail are no atomics so the comparison may return
inexact results. However, this doesn't matter here as user-space would
need to poll() in two threads simultaneously to trigger this. And in this
case it doesn't matter if a cached result is returned or the exact new
result as user-space does not know which thread returns first from poll()
and the following read(). So it is safe to compare the values without
locking.
Signed-off-by: NDavid Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

When receiving messages from the HID subsystem, we need to process them
and store them in an internal buffer so user-space can read() on the char
device to retrieve the messages.

This adds a static buffer for 32 messages to each uhid device. Each
message is dynamically allocated so the uhid_device structure does not get
too big.

uhid_queue() adds a message to the buffer. If the buffer is full, the
message is discarded. uhid_queue_event() is an helper for messages without
payload.

This also adds a public header: uhid.h. It contains the declarations for
the user-space API. It is built around "struct uhid_event" which contains
a type field which specifies the event type and each event can then add a
variable-length payload. For now, there is only a dummy event but later
patches will add new event types and payloads.
Signed-off-by: NDavid Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

This adds a dummy driver that will support user-space I/O drivers for the
HID subsystem. This allows to write transport-level drivers like USB-HID
and Bluetooth-HID in user-space.

Low-Energy Bluetooth needs this to feed HID data that is parsed in
user-space back into the kernel.
Signed-off-by: NDavid Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>