RedBear-OS/local/patches/base/absorbed/P0-inputd-per-device-consumers.patch

diff --git a/drivers/inputd/src/main.rs b/drivers/inputd/src/main.rs
--- a/drivers/inputd/src/main.rs
+++ b/drivers/inputd/src/main.rs
@@ -17,7 +17,7 @@
 use std::mem::transmute;
 use std::sync::atomic::{AtomicUsize, Ordering};
 
-use inputd::{ControlEvent, VtEvent, VtEventKind};
+use inputd::{ControlEvent, HotplugEventHeader, VtEvent, VtEventKind};
 
 use libredox::errno::ESTALE;
 use redox_scheme::scheme::{SchemeState, SchemeSync};
@@ -47,6 +47,17 @@
         notified: bool,
         vt: usize,
     },
+    DeviceConsumer {
+        device_name: String,
+        events: EventFlags,
+        pending: Vec<u8>,
+        notified: bool,
+    },
+    HotplugEvents {
+        events: EventFlags,
+        pending: Vec<u8>,
+        notified: bool,
+    },
     Display {
         events: EventFlags,
         pending: Vec<VtEvent>,
@@ -88,6 +99,9 @@
     "control",
 ];
 
+const DEVICE_ADD: u32 = 1;
+const DEVICE_REMOVE: u32 = 2;
+
 enum ProducerKind {
     Legacy,
     Named(String),
@@ -116,7 +130,7 @@
     }
 
     fn register_named_producer(&mut self, name: &str) -> syscall::Result<Handle> {
-        if name.is_empty() || RESERVED_DEVICE_NAMES.contains(&name) {
+        if name.is_empty() || name.contains('/') || RESERVED_DEVICE_NAMES.contains(&name) {
             return Err(SysError::new(EINVAL));
         }
 
@@ -126,11 +140,57 @@
 
         let device_id = self.next_device_id.fetch_add(1, Ordering::SeqCst) as u32;
         self.devices.insert(name.to_owned(), device_id);
+        self.queue_hotplug_event(DEVICE_ADD, device_id, name)?;
         Ok(Handle::NamedProducer {
             name: name.to_owned(),
         })
     }
 
+    fn drain_pending_bytes(pending: &mut Vec<u8>, buf: &mut [u8]) -> usize {
+        let copy = core::cmp::min(pending.len(), buf.len());
+
+        for (i, byte) in pending.drain(..copy).enumerate() {
+            buf[i] = byte;
+        }
+
+        copy
+    }
+
+    fn queue_hotplug_event(
+        &mut self,
+        kind: u32,
+        device_id: u32,
+        name: &str,
+    ) -> syscall::Result<()> {
+        let name_len = u32::try_from(name.len()).map_err(|_| SysError::new(EINVAL))?;
+        let header = HotplugEventHeader {
+            kind,
+            device_id,
+            name_len,
+            _reserved: 0,
+        };
+        let header_bytes = unsafe {
+            core::slice::from_raw_parts(
+                (&header as *const HotplugEventHeader).cast::<u8>(),
+                size_of::<HotplugEventHeader>(),
+            )
+        };
+
+        for handle in self.handles.values_mut() {
+            if let Handle::HotplugEvents {
+                pending, notified, ..
+            } = handle
+            {
+                pending.extend_from_slice(header_bytes);
+                pending.extend_from_slice(name.as_bytes());
+                *notified = false;
+            }
+        }
+
+        self.has_new_events = true;
+        Ok(())
+    }
+
     fn route_legacy_consumer_events(&mut self, buf: &[u8]) {
         if let Some(active_vt) = self.active_vt {
             for handle in self.handles.values_mut() {
@@ -150,9 +210,21 @@
         }
     }
 
-    fn route_named_producer_events(&mut self, _name: &str, _buf: &[u8]) {
-        // DeviceConsumer routing is added in a follow-up patch. Named producers already share the
-        // legacy consumer path, so existing callers continue to receive these events.
+    fn route_named_producer_events(&mut self, name: &str, buf: &[u8]) {
+        for handle in self.handles.values_mut() {
+            match handle {
+                Handle::DeviceConsumer {
+                    device_name,
+                    pending,
+                    notified,
+                    ..
+                } if device_name == name => {
+                    pending.extend_from_slice(buf);
+                    *notified = false;
+                }
+                _ => continue,
+            }
+        }
     }
 
     fn switch_vt(&mut self, new_active: usize) {
@@ -324,7 +396,24 @@
                     is_earlyfb: command == "handle_early",
                 }
             }
+            "events" if path_parts.next().is_none() => Handle::HotplugEvents {
+                events: EventFlags::empty(),
+                pending: Vec::new(),
+                notified: false,
+            },
             "control" => Handle::Control,
+            device_name
+                if !device_name.is_empty()
+                    && !RESERVED_DEVICE_NAMES.contains(&device_name)
+                    && path_parts.next().is_none() =>
+            {
+                Handle::DeviceConsumer {
+                    device_name: device_name.to_owned(),
+                    events: EventFlags::empty(),
+                    pending: Vec::new(),
+                    notified: false,
+                }
+            }
 
             _ => {
                 log::error!("invalid path '{path}'");
@@ -380,13 +469,11 @@
                     return Err(SysError::new(ESTALE));
                 }
 
-                let copy = core::cmp::min(pending.len(), buf.len());
-
-                for (i, byte) in pending.drain(..copy).enumerate() {
-                    buf[i] = byte;
-                }
+                Ok(Self::drain_pending_bytes(pending, buf))
+            }
 
-                Ok(copy)
+            Handle::DeviceConsumer { pending, .. } | Handle::HotplugEvents { pending, .. } => {
+                Ok(Self::drain_pending_bytes(pending, buf))
             }
 
             Handle::Display { pending, .. } => {
@@ -453,6 +540,10 @@
                 log::error!("consumer tried to write");
                 return Err(SysError::new(EINVAL));
             }
+            Handle::DeviceConsumer { .. } | Handle::HotplugEvents { .. } => {
+                log::error!("consumer or hotplug handle tried to write");
+                return Err(SysError::new(EINVAL));
+            }
             Handle::Display { .. } => {
                 log::error!("display tried to write");
                 return Err(SysError::new(EINVAL));
@@ -541,6 +632,16 @@
                 ref mut events,
                 ref mut notified,
                 ..
+            }
+            | Handle::DeviceConsumer {
+                ref mut events,
+                ref mut notified,
+                ..
+            }
+            | Handle::HotplugEvents {
+                ref mut events,
+                ref mut notified,
+                ..
             } => {
                 *events = flags;
                 *notified = false;
@@ -571,7 +672,12 @@
 
         match handle {
             Handle::NamedProducer { name } => {
-                self.devices.remove(&name);
+                if let Some(device_id) = self.devices.remove(&name) {
+                    self.queue_hotplug_event(DEVICE_REMOVE, device_id, &name)
+                        .unwrap_or_else(|err| {
+                            log::error!("failed to queue removal hotplug event for {name}: {err}");
+                        });
+                }
             }
             Handle::Consumer { vt, .. } => {
                 self.vts.remove(&vt);
@@ -658,6 +764,28 @@
                     socket_file.write_response(
                         Response::post_fevent(*id, EventFlags::EVENT_READ.bits()),
                         SignalBehavior::Restart,
+                    )?;
+
+                    *notified = true;
+                }
+                Handle::DeviceConsumer {
+                    events,
+                    pending,
+                    ref mut notified,
+                    ..
+                }
+                | Handle::HotplugEvents {
+                    events,
+                    pending,
+                    ref mut notified,
+                } => {
+                    if pending.is_empty() || *notified || !events.contains(EventFlags::EVENT_READ) {
+                        continue;
+                    }
+
+                    socket_file.write_response(
+                        Response::post_fevent(*id, EventFlags::EVENT_READ.bits()),
+                        SignalBehavior::Restart,
                     )?;
 
                     *notified = true;
diff --git a/drivers/inputd/src/lib.rs b/drivers/inputd/src/lib.rs
--- a/drivers/inputd/src/lib.rs
+++ b/drivers/inputd/src/lib.rs
@@ -1,5 +1,5 @@
 use std::fs::{File, OpenOptions};
-use std::io::{self, Read, Write};
+use std::io::{self, ErrorKind, Read, Write};
 use std::mem::size_of;
 use std::os::fd::{AsFd, AsRawFd, BorrowedFd, FromRawFd, RawFd};
 use std::os::unix::fs::OpenOptionsExt;
@@ -31,6 +31,24 @@
     slice::from_raw_parts_mut((p as *mut T) as *mut u8, size_of::<T>())
 }
 
+fn validate_input_name(kind: &str, name: &str) -> io::Result<()> {
+    if name.is_empty() {
+        return Err(io::Error::new(
+            io::ErrorKind::InvalidInput,
+            format!("input {kind} name must not be empty"),
+        ));
+    }
+
+    if name.contains('/') {
+        return Err(io::Error::new(
+            io::ErrorKind::InvalidInput,
+            format!("input {kind} name must not contain '/'"),
+        ));
+    }
+
+    Ok(())
+}
+
 pub struct ConsumerHandle(File);
 
 pub enum ConsumerHandleEvent<'a> {
@@ -197,6 +215,22 @@
     pub vt: usize,
 }
 
+#[derive(Debug, Clone, Copy)]
+#[repr(C)]
+pub struct HotplugEventHeader {
+    pub kind: u32,
+    pub device_id: u32,
+    pub name_len: u32,
+    pub _reserved: u32,
+}
+
+#[derive(Debug, Clone)]
+pub struct HotplugEvent {
+    pub kind: u32,
+    pub device_id: u32,
+    pub name: String,
+}
+
 /// Handle for opening a named producer on the input scheme.
 /// Opens /scheme/input/producer/{name}
 pub struct NamedProducerHandle {
@@ -205,19 +239,7 @@
 
 impl NamedProducerHandle {
     pub fn new(name: &str) -> io::Result<Self> {
-        if name.is_empty() {
-            return Err(io::Error::new(
-                io::ErrorKind::InvalidInput,
-                "input producer name must not be empty",
-            ));
-        }
-
-        if name.contains('/') {
-            return Err(io::Error::new(
-                io::ErrorKind::InvalidInput,
-                "input producer name must not contain '/'",
-            ));
-        }
+        validate_input_name("producer", name)?;
 
         let path = format!("/scheme/input/producer/{name}");
         File::open(path).map(|fd| Self { fd })
@@ -229,6 +251,124 @@
     }
 }
 
+pub struct DeviceConsumerHandle {
+    fd: File,
+}
+
+impl DeviceConsumerHandle {
+    pub fn new(device_name: &str) -> io::Result<Self> {
+        validate_input_name("device", device_name)?;
+
+        let fd = OpenOptions::new()
+            .read(true)
+            .custom_flags(O_NONBLOCK as i32)
+            .open(format!("/scheme/input/{device_name}"))?;
+
+        Ok(Self { fd })
+    }
+
+    pub fn event_handle(&self) -> BorrowedFd<'_> {
+        self.fd.as_fd()
+    }
+
+    pub fn read_event(&mut self) -> io::Result<Option<orbclient::Event>> {
+        let mut raw = [0_u8; size_of::<orbclient::Event>()];
+
+        match self.fd.read(&mut raw) {
+            Ok(0) => Ok(None),
+            Ok(read) => {
+                assert_eq!(read, raw.len());
+                Ok(Some(unsafe {
+                    core::ptr::read_unaligned(raw.as_ptr().cast::<orbclient::Event>())
+                }))
+            }
+            Err(err) if err.kind() == ErrorKind::WouldBlock => Ok(None),
+            Err(err) => Err(err),
+        }
+    }
+}
+
+pub struct HotplugHandle {
+    fd: File,
+    partial: Vec<u8>,
+}
+
+impl HotplugHandle {
+    pub fn new() -> io::Result<Self> {
+        let fd = OpenOptions::new()
+            .read(true)
+            .custom_flags(O_NONBLOCK as i32)
+            .open("/scheme/input/events")?;
+
+        Ok(Self {
+            fd,
+            partial: Vec::new(),
+        })
+    }
+
+    pub fn event_handle(&self) -> BorrowedFd<'_> {
+        self.fd.as_fd()
+    }
+
+    pub fn read_event(&mut self) -> io::Result<Option<HotplugEvent>> {
+        let mut buf = [0_u8; 1024];
+
+        loop {
+            if let Some(event) = Self::try_parse_event(&mut self.partial)? {
+                return Ok(Some(event));
+            }
+
+            match self.fd.read(&mut buf) {
+                Ok(0) => return Ok(None),
+                Ok(read) => self.partial.extend_from_slice(&buf[..read]),
+                Err(err) if err.kind() == ErrorKind::WouldBlock => return Ok(None),
+                Err(err) => return Err(err),
+            }
+        }
+    }
+
+    fn try_parse_event(partial: &mut Vec<u8>) -> io::Result<Option<HotplugEvent>> {
+        if partial.len() < size_of::<HotplugEventHeader>() {
+            return Ok(None);
+        }
+
+        let header =
+            unsafe { core::ptr::read_unaligned(partial.as_ptr().cast::<HotplugEventHeader>()) };
+        let name_len = usize::try_from(header.name_len).map_err(|_| {
+            io::Error::new(
+                io::ErrorKind::InvalidData,
+                "invalid input hotplug name length",
+            )
+        })?;
+        let total_len = size_of::<HotplugEventHeader>()
+            .checked_add(name_len)
+            .ok_or_else(|| {
+                io::Error::new(io::ErrorKind::InvalidData, "input hotplug event too large")
+            })?;
+
+        if partial.len() < total_len {
+            return Ok(None);
+        }
+
+        let name = std::str::from_utf8(&partial[size_of::<HotplugEventHeader>()..total_len])
+            .map_err(|_| {
+                io::Error::new(
+                    io::ErrorKind::InvalidData,
+                    "input hotplug name is not UTF-8",
+                )
+            })?
+            .to_owned();
+
+        partial.drain(..total_len);
+
+        Ok(Some(HotplugEvent {
+            kind: header.kind,
+            device_id: header.device_id,
+            name,
+        }))
+    }
+}
+
 pub struct ProducerHandle(File);
 
 impl ProducerHandle {