[PATCH 0/5] virt: Add Bao hypervisor IPC and I/O dispatcher drivers

[PATCH 0/5] virt: Add Bao hypervisor IPC and I/O dispatcher drivers

[joaopeixoto]

From: João Peixoto <joaopeixoto@osyx.tech>

This series introduces support for the Bao hypervisor guest-side drivers
under drivers/virt/bao and the associated Device Tree bindings, UAPI,
and MAINTAINERS entries.

Bao is a lightweight static-partitioning hypervisor for embedded and
safety-critical systems. This series adds:
- The Bao IPC shared memory driver, which enables Linux guests to
  communicate with each other through shared memory regions.
- The Bao I/O Dispatcher driver, which allows Bao's VMs to share I/O
  devices using device paravirtualization (VirtIO).

Patch overview:

1. dt-bindings: Add Bao IPC shared memory driver binding
   - Provides a standardized DT description for Bao IPC shared memory
     devices used for inter-VM communication.

2. virt: add Bao IPC shared memory driver
   - Character device driver that maps shared-memory regions and
     communicates with the hypervisor via architecture-specific hypercalls
     (SMC/HVC on ARM, SBI ecall on RISC-V).

3. dt-bindings: Add Bao I/O dispatcher driver binding
   - DT binding for the Bao I/O Dispatcher, describing memory regions,
     interrupts, and compatible strings for backend VMs.

4. virt: add Bao I/O dispatcher driver
   - Implements the I/O Dispatcher kernel module bridging Bao Remote I/O
     with VirtIO backend devices.
   - Includes architecture-specific headers for ARM, ARM64, and RISC-V,
     driver framework files, UAPI headers, Kconfig/Makefile integration,
     and ioctl documentation.

5. MAINTAINERS: Add entries for Bao hypervisor drivers
   - Registers maintainers for all Bao hypervisor components to ensure
     proper kernel review and notifications.

This series has been validated on Linux guests running under Bao hypervisor,
ensuring correct initialization, read/write operations for IPC shared
memory, and proper I/O Dispatcher functionality for backend VMs.

Feedback and review from maintainers of virtualization, architecture-specific
code (ARM, ARM64, RISC-V), Device Tree bindings, and UAPI are welcome.

João Peixoto (5):
  dt-bindings: Add Bao IPC shared memory driver binding
  virt: add Bao IPC shared memory driver
  dt-bindings: Add Bao I/O dispatcher driver binding
  virt: add Bao I/O dispatcher driver
  MAINTAINERS: Add entries for Bao hypervisor drivers, headers, and DT
    bindings

 .../bindings/bao/io-dispatcher.yaml           |  67 +++
 .../devicetree/bindings/bao/ipcshmem.yaml     |  99 ++++
 .../devicetree/bindings/vendor-prefixes.yaml  |   2 +
 .../userspace-api/ioctl/ioctl-number.rst      |   2 +
 MAINTAINERS                                   |  12 +
 arch/arm/include/asm/bao.h                    |  62 ++
 arch/arm64/include/asm/bao.h                  |  62 ++
 arch/riscv/include/asm/bao.h                  |  61 ++
 drivers/virt/Kconfig                          |   2 +
 drivers/virt/Makefile                         |   2 +
 drivers/virt/bao/Kconfig                      |   5 +
 drivers/virt/bao/Makefile                     |   4 +
 drivers/virt/bao/io-dispatcher/Kconfig        |  16 +
 drivers/virt/bao/io-dispatcher/Makefile       |   4 +
 drivers/virt/bao/io-dispatcher/bao_drv.h      | 386 +++++++++++++
 drivers/virt/bao/io-dispatcher/dm.c           | 330 +++++++++++
 drivers/virt/bao/io-dispatcher/driver.c       | 348 +++++++++++
 drivers/virt/bao/io-dispatcher/hypercall.h    |  30 +
 drivers/virt/bao/io-dispatcher/intc.c         |  68 +++
 drivers/virt/bao/io-dispatcher/io_client.c    | 435 ++++++++++++++
 .../virt/bao/io-dispatcher/io_dispatcher.c    | 207 +++++++
 drivers/virt/bao/io-dispatcher/ioctls.c       | 145 +++++
 drivers/virt/bao/io-dispatcher/ioeventfd.c    | 336 +++++++++++
 drivers/virt/bao/io-dispatcher/irqfd.c        | 341 +++++++++++
 drivers/virt/bao/ipcshmem/Kconfig             |   9 +
 drivers/virt/bao/ipcshmem/Makefile            |   3 +
 drivers/virt/bao/ipcshmem/ipcshmem.c          | 539 ++++++++++++++++++
 include/uapi/linux/bao.h                      | 124 ++++
 28 files changed, 3701 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/bao/io-dispatcher.yaml
 create mode 100644 Documentation/devicetree/bindings/bao/ipcshmem.yaml
 create mode 100644 arch/arm/include/asm/bao.h
 create mode 100644 arch/arm64/include/asm/bao.h
 create mode 100644 arch/riscv/include/asm/bao.h
 create mode 100644 drivers/virt/bao/Kconfig
 create mode 100644 drivers/virt/bao/Makefile
 create mode 100644 drivers/virt/bao/io-dispatcher/Kconfig
 create mode 100644 drivers/virt/bao/io-dispatcher/Makefile
 create mode 100644 drivers/virt/bao/io-dispatcher/bao_drv.h
 create mode 100644 drivers/virt/bao/io-dispatcher/dm.c
 create mode 100644 drivers/virt/bao/io-dispatcher/driver.c
 create mode 100644 drivers/virt/bao/io-dispatcher/hypercall.h
 create mode 100644 drivers/virt/bao/io-dispatcher/intc.c
 create mode 100644 drivers/virt/bao/io-dispatcher/io_client.c
 create mode 100644 drivers/virt/bao/io-dispatcher/io_dispatcher.c
 create mode 100644 drivers/virt/bao/io-dispatcher/ioctls.c
 create mode 100644 drivers/virt/bao/io-dispatcher/ioeventfd.c
 create mode 100644 drivers/virt/bao/io-dispatcher/irqfd.c
 create mode 100644 drivers/virt/bao/ipcshmem/Kconfig
 create mode 100644 drivers/virt/bao/ipcshmem/Makefile
 create mode 100644 drivers/virt/bao/ipcshmem/ipcshmem.c
 create mode 100644 include/uapi/linux/bao.h

-- 
2.43.0

[PATCH 1/5] dt-bindings: Add Bao IPC shared memory driver binding

[joaopeixoto]

From: João Peixoto <joaopeixoto@osyx.tech>

This patch adds a Device Tree binding for the Bao IPC shared memory
device, which provides a standardized description of the hardware
interface used for inter-VM communication in Bao-based systems.

The binding documents the following properties:

  - compatible: "bao,ipcshmem"
  - reg: Memory region for the shared memory device
  - id: Unique device identifier
  - read-channel: [offset, size] for reading from the shared memory
  - write-channel: [offset, size] for writing to the shared memory
  - interrupts: Interrupts used by the device

This enables kernel drivers and userspace tools to correctly
instantiate and configure Bao IPC shared memory devices based
on the DT description, facilitating efficient communication
between VMs.

Signed-off-by: João Peixoto <joaopeixoto@osyx.tech>
---
 .../devicetree/bindings/bao/ipcshmem.yaml     | 99 +++++++++++++++++++
 .../devicetree/bindings/vendor-prefixes.yaml  |  2 +
 2 files changed, 101 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/bao/ipcshmem.yaml

diff --git a/Documentation/devicetree/bindings/bao/ipcshmem.yaml b/Documentation/devicetree/bindings/bao/ipcshmem.yaml
new file mode 100644
index 000000000000..398ac610c29f
--- /dev/null
+++ b/Documentation/devicetree/bindings/bao/ipcshmem.yaml
@@ -0,0 +1,99 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/bao/ipcshmem.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: Bao IPC Shared Memory Device
+
+maintainers:
+  - José Martins <jose@osyx.tech>
+  - David Cerdeira <davidmcerdeira@osyx.tech>
+  - João Peixoto <joaopeixoto@osyx.tech>
+
+description: |
+  Shared memory based communication device for Bao hypervisor guests.
+  It allows the kernel to interface with guests running under
+	the Bao hypervisor, providing a character device interface
+	for exchanging data through dedicated shared-memory regions.
+
+properties:
+  compatible:
+    const: "bao,ipcshmem"
+
+  reg:
+    description: |
+      Memory resource for the shared memory device.
+    maxItems: 4
+    type: array
+    items:
+      type: integer
+
+  id:
+    description: Driver instance ID
+    type: integer
+    minimum: 0
+
+  read-channel:
+    description: |
+      Defines the shared-memory region used by the guest → host data path.
+
+      The value is a 2-cell array describing a sub-region inside the main
+      `reg` area:
+        - The first cell is the byte offset from the beginning of the
+          shared-memory region specified in `reg`.
+        - The second cell is the size of the readable region in bytes.
+
+      The driver will only read data from this sub-region.
+    type: array
+    items:
+      type: integer
+    minItems: 2
+    maxItems: 2
+
+  write-channel:
+    description: |
+      Defines the shared-memory region used by the host → guest data path.
+
+      The value is a 2-cell array describing a sub-region inside the main
+      `reg` area:
+        - The first cell is the byte offset from the beginning of the
+          shared-memory region specified in `reg`.
+        - The second cell is the size of the writable region in bytes.
+
+      The driver will only write data into this sub-region.
+    type: array
+    items:
+      type: integer
+    minItems: 2
+    maxItems: 2
+
+  interrupts:
+    description: |
+      Interrupt specification for the device.
+    type: array
+    items:
+      type: integer
+    minItems: 3
+    maxItems: 3
+
+required:
+  - compatible
+  - reg
+  - id
+  - read-channel
+  - write-channel
+  - interrupts
+
+additionalProperties: false
+
+examples:
+  - |
+    bao-ipc@f0000000 {
+        compatible = "bao,ipcshmem";
+        reg = <0x0 0xf0000000 0x0 0x00010000>;
+        read-channel = <0x0 0x2000>;
+        write-channel = <0x2000 0x2000>;
+        interrupts = <0 52 1>;
+        id = <0>;
+    };
diff --git a/Documentation/devicetree/bindings/vendor-prefixes.yaml b/Documentation/devicetree/bindings/vendor-prefixes.yaml
index c7591b2aec2a..c047fbd6b91a 100644
--- a/Documentation/devicetree/bindings/vendor-prefixes.yaml
+++ b/Documentation/devicetree/bindings/vendor-prefixes.yaml
@@ -223,6 +223,8 @@ patternProperties:
     description: Shenzhen AZW Technology Co., Ltd.
   "^baikal,.*":
     description: BAIKAL ELECTRONICS, JSC
+  "^bao,.*":
+    description: Bao Hypervisor
   "^bananapi,.*":
     description: BIPAI KEJI LIMITED
   "^beacon,.*":
-- 
2.43.0

[PATCH 2/5] virt: add Bao IPC shared memory driver

[joaopeixoto]

From: João Peixoto <joaopeixoto@osyx.tech>

Add a new driver providing an interface for communication with guests
hosted by the Bao hypervisor using shared-memory channels. The driver
exposes read/write regions defined in device tree and notifies the
hypervisor via an architecture-specific hypercall (SMC/HVC on ARM and
SBI ecall on RISC-V).

The patch introduces:
  - drivers/bao/ with the initial Bao IPC shared-memory implementation
  - Kconfig entry enabling BAO_SHMEM
  - Makefile integration for building the driver
  - A character device interface supporting mmap(), read(), and write()
  - Platform driver support using DT properties for channel layout

Each device instance maps its assigned shared-memory region, validates
read/write channel configuration, and exposes a /dev/baoipc<N> node
used by user space to exchange data with Bao guests.

Signed-off-by: João Peixoto <joaopeixoto@osyx.tech>
---
 drivers/virt/Kconfig                 |   2 +
 drivers/virt/Makefile                |   1 +
 drivers/virt/bao/Kconfig             |   3 +
 drivers/virt/bao/Makefile            |   3 +
 drivers/virt/bao/ipcshmem/Kconfig    |   9 +
 drivers/virt/bao/ipcshmem/Makefile   |   3 +
 drivers/virt/bao/ipcshmem/ipcshmem.c | 539 +++++++++++++++++++++++++++
 7 files changed, 560 insertions(+)
 create mode 100644 drivers/virt/bao/Kconfig
 create mode 100644 drivers/virt/bao/Makefile
 create mode 100644 drivers/virt/bao/ipcshmem/Kconfig
 create mode 100644 drivers/virt/bao/ipcshmem/Makefile
 create mode 100644 drivers/virt/bao/ipcshmem/ipcshmem.c

diff --git a/drivers/virt/Kconfig b/drivers/virt/Kconfig
index 52eb7e4ba71f..cb98c4c52fd1 100644
--- a/drivers/virt/Kconfig
+++ b/drivers/virt/Kconfig
@@ -47,6 +47,8 @@ source "drivers/virt/nitro_enclaves/Kconfig"
 
 source "drivers/virt/acrn/Kconfig"
 
+source "drivers/virt/bao/Kconfig"
+
 endif
 
 source "drivers/virt/coco/Kconfig"
diff --git a/drivers/virt/Makefile b/drivers/virt/Makefile
index f29901bd7820..623a671f8711 100644
--- a/drivers/virt/Makefile
+++ b/drivers/virt/Makefile
@@ -10,3 +10,4 @@ obj-y				+= vboxguest/
 obj-$(CONFIG_NITRO_ENCLAVES)	+= nitro_enclaves/
 obj-$(CONFIG_ACRN_HSM)		+= acrn/
 obj-y				+= coco/
+obj-$(CONFIG_BAO_SHMEM)		+= bao/
diff --git a/drivers/virt/bao/Kconfig b/drivers/virt/bao/Kconfig
new file mode 100644
index 000000000000..4f7929d57475
--- /dev/null
+++ b/drivers/virt/bao/Kconfig
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+source "drivers/virt/bao/ipcshmem/Kconfig"
diff --git a/drivers/virt/bao/Makefile b/drivers/virt/bao/Makefile
new file mode 100644
index 000000000000..68f5d3f282c4
--- /dev/null
+++ b/drivers/virt/bao/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_BAO_SHMEM) += ipcshmem/
diff --git a/drivers/virt/bao/ipcshmem/Kconfig b/drivers/virt/bao/ipcshmem/Kconfig
new file mode 100644
index 000000000000..42690073e819
--- /dev/null
+++ b/drivers/virt/bao/ipcshmem/Kconfig
@@ -0,0 +1,9 @@
+# SPDX-License-Identifier: GPL-2.0
+config BAO_SHMEM
+	tristate "Bao hypervisor shared memory support"
+
+	help
+	This enables support for Bao shared memory communication.
+	It allows the kernel to interface with guests running under
+	the Bao hypervisor, providing a character device interface
+	for exchanging data through dedicated shared-memory regions.
diff --git a/drivers/virt/bao/ipcshmem/Makefile b/drivers/virt/bao/ipcshmem/Makefile
new file mode 100644
index 000000000000..e027dcdb06aa
--- /dev/null
+++ b/drivers/virt/bao/ipcshmem/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_BAO_SHMEM) += bao.o
+bao-objs += ipcshmem.o
diff --git a/drivers/virt/bao/ipcshmem/ipcshmem.c b/drivers/virt/bao/ipcshmem/ipcshmem.c
new file mode 100644
index 000000000000..cadb79bfca6e
--- /dev/null
+++ b/drivers/virt/bao/ipcshmem/ipcshmem.c
@@ -0,0 +1,539 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Bao Hypervisor IPC Through Shared-memory Driver
+ *
+ * Copyright (c) Bao Project and Contributors. All rights reserved.
+ *
+ * Authors:
+ *	David Cerdeira <davidmcerdeira@osyx.tech>
+ *	José Martins <jose@osyx.tech>
+ *	João Peixoto <joaopeixoto@osyx.tech>
+ */
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/uaccess.h>
+#include <linux/fs.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+#include <linux/interrupt.h>
+#include <linux/of.h>
+#include <linux/io.h>
+#include <linux/mutex.h>
+#include <linux/poll.h>
+#include <linux/platform_device.h>
+#include <linux/ioctl.h>
+#include <linux/cdev.h>
+#include <linux/device.h>
+#include <linux/spinlock.h>
+#include <linux/mutex.h>
+#include <linux/wait.h>
+#include <linux/mm.h>
+
+#if defined(CONFIG_ARM64) || defined(CONFIG_ARM)
+#include <linux/arm-smccc.h>
+#include <asm/memory.h>
+#elif CONFIG_RISCV
+#include <asm/sbi.h>
+#endif
+
+#define DEV_NAME "baoipc"
+#define MAX_DEVICES 16
+#define NAME_LEN 32
+
+static dev_t bao_ipcshmem_devt;
+struct class *cl;
+
+/**
+ * struct bao_ipcshmem - Bao IPC shared memory device
+ * @cdev: Character device interface
+ * @dev: Device structure
+ * @id: Device instance ID
+ * @label: Name/label of the device
+ * @read_base: Base address of the read channel
+ * @read_size: Size of the read channel
+ * @write_base: Base address of the write channel
+ * @write_size: Size of the write channel
+ * @physical_base: Physical memory base address
+ * @shmem_size: Total size of the shared memory region
+ */
+struct bao_ipcshmem {
+	struct cdev cdev;
+	struct device *dev;
+	int id;
+	char label[NAME_LEN];
+	void *read_base;
+	size_t read_size;
+	void *write_base;
+	size_t write_size;
+	phys_addr_t *physical_base;
+	size_t shmem_size;
+};
+
+#ifdef CONFIG_ARM64
+/**
+ * bao_ipcshmem_notify - Notify the Bao hypervisor of an IPC shared memory event (ARM64)
+ * @dev: IPC shared memory device
+ *
+ * Executes a fast SMC hypercall to notify the hypervisor of an event
+ * associated with the given IPC shared memory device.
+ *
+ * Return: Hypercall return value.
+ */
+static uint64_t bao_ipcshmem_notify(struct bao_ipcshmem *dev)
+{
+	register uint64_t x0 asm("x0") =
+		ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_64,
+				   ARM_SMCCC_OWNER_VENDOR_HYP, 1);
+	register uint64_t x1 asm("x1") = dev->id;
+	register uint64_t x2 asm("x2") = 0;
+
+	asm volatile("hvc 0\t\n" : "=r"(x0) : "r"(x0), "r"(x1), "r"(x2));
+
+	return x0;
+}
+#elif CONFIG_ARM
+/**
+ * bao_ipcshmem_notify - Notify the Bao hypervisor of an IPC shared memory event (ARM)
+ * @dev: IPC shared memory device
+ *
+ * Executes a fast SMC hypercall to notify the hypervisor of an event
+ * associated with the given IPC shared memory device.
+ *
+ * Return: Hypercall return value.
+ */
+static uint32_t bao_ipcshmem_notify(struct bao_ipcshmem *dev)
+{
+	register uint32_t r0 asm("r0") =
+		ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_32,
+				   ARM_SMCCC_OWNER_VENDOR_HYP, 1);
+	register uint32_t r1 asm("r1") = dev->id;
+	register uint32_t r2 asm("r2") = 0;
+
+	asm volatile("hvc #0\t\n" : "=r"(r0) : "r"(r0), "r"(r1), "r"(r2));
+
+	return r0;
+}
+#elif CONFIG_RISCV
+/**
+ * bao_ipcshmem_notify - Notify the Bao hypervisor of an IPC shared memory event (RISC-V)
+ * @dev: IPC shared memory device
+ *
+ * Executes an SBI call to notify the Bao hypervisor of an IPC shared memory event.
+ *
+ * Return: SBI call error code.
+ */
+static uint64_t bao_ipcshmem_notify(struct bao_ipcshmem *dev)
+{
+	struct sbiret ret = sbi_ecall(0x08000ba0, 1, dev->id, 0, 0, 0, 0, 0);
+
+	return ret.error;
+}
+#endif
+
+/**
+ * bao_ipcshmem_mmap_fops - mmap handler for IPC shared memory
+ * @filp: File pointer
+ * @vma: Virtual memory area
+ *
+ * Maps the physical shared memory of the Bao IPC device into
+ * userspace using remap_pfn_range.
+ *
+ * Return: 0 on success, -EFAULT on failure.
+ */
+static int bao_ipcshmem_mmap_fops(struct file *filp, struct vm_area_struct *vma)
+{
+	struct bao_ipcshmem *bao = filp->private_data;
+	unsigned long vsize = vma->vm_end - vma->vm_start;
+	unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
+	phys_addr_t paddr;
+
+	if (WARN_ON_ONCE(!bao))
+		return -ENODEV;
+
+	if (!vsize)
+		return -EINVAL;
+
+	if (offset >= bao->shmem_size)
+		return -EINVAL;
+
+	if (vsize > bao->shmem_size - offset)
+		return -EINVAL;
+
+	paddr = (phys_addr_t)bao->physical_base + offset;
+
+	if (!PAGE_ALIGNED(paddr))
+		return -EINVAL;
+
+	if (remap_pfn_range(vma, vma->vm_start,
+			    paddr >> PAGE_SHIFT,
+			    vsize, vma->vm_page_prot))
+		return -EFAULT;
+
+	return 0;
+}
+
+/**
+ * bao_ipcshmem_read_fops - read handler for IPC shared memory
+ * @filp: File pointer
+ * @buf: Userspace buffer
+ * @count: Number of bytes to read
+ * @ppos: File offset
+ *
+ * Copies data from the Bao IPC read buffer to userspace.
+ *
+ * Return: Number of bytes read, or 0 if EOF.
+ */
+static ssize_t bao_ipcshmem_read_fops(struct file *filp, char __user *buf,
+				      size_t count, loff_t *ppos)
+{
+	struct bao_ipcshmem *bao = filp->private_data;
+	size_t available;
+
+	if (WARN_ON_ONCE(!bao || !buf || !ppos))
+		return -EINVAL;
+
+	if (*ppos >= bao->read_size)
+		return 0;
+
+	available = bao->read_size - *ppos;
+	if (count > available)
+		count = available;
+
+	if (copy_to_user(buf, bao->read_base + *ppos, count))
+		return -EFAULT;
+
+	*ppos += count;
+	return count;
+}
+
+/**
+ * bao_ipcshmem_write_fops - write handler for IPC shared memory
+ * @filp: File pointer
+ * @buf: Userspace buffer
+ * @count: Number of bytes to write
+ * @ppos: File offset
+ *
+ * Copies data from userspace to the Bao IPC write buffer and
+ * notifies the hypervisor of the update.
+ *
+ * Return: Number of bytes written.
+ */
+static ssize_t bao_ipcshmem_write_fops(struct file *filp, const char __user *buf,
+				       size_t count, loff_t *ppos)
+{
+	struct bao_ipcshmem *bao = filp->private_data;
+	size_t avail;
+
+	if (WARN_ON_ONCE(!bao || !buf || !ppos))
+		return -EINVAL;
+
+	if (*ppos >= bao->write_size)
+		return 0;
+
+	avail = bao->write_size - *ppos;
+	if (count > avail)
+		count = avail;
+
+	if (copy_from_user(bao->write_base + *ppos, buf, count))
+		return -EFAULT;
+
+	*ppos += count;
+
+	/* Notify any listeners that new data is available */
+	bao_ipcshmem_notify(bao);
+
+	return count;
+}
+
+/**
+ * bao_ipcshmem_open_fops - open handler for IPC shared memory
+ * @inode: Inode pointer
+ * @filp: File pointer
+ *
+ * Associates the file with the Bao IPC device and increments
+ * the kobject reference.
+ *
+ * Return: 0 on success.
+ */
+static int bao_ipcshmem_open_fops(struct inode *inode, struct file *filp)
+{
+	struct bao_ipcshmem *bao;
+
+	if (WARN_ON_ONCE(!inode || !filp))
+		return -EINVAL;
+
+	bao = container_of(inode->i_cdev, struct bao_ipcshmem, cdev);
+	filp->private_data = bao;
+
+	kobject_get(&bao->dev->kobj);
+
+	return 0;
+}
+
+/**
+ * bao_ipcshmem_release_fops - release handler for IPC shared memory
+ * @inode: Inode pointer
+ * @filp: File pointer
+ *
+ * Disassociates the file from the Bao IPC device and decrements
+ * the kobject reference.
+ *
+ * Return: 0 on success.
+ */
+static int bao_ipcshmem_release_fops(struct inode *inode, struct file *filp)
+{
+	struct bao_ipcshmem *bao;
+
+	if (WARN_ON_ONCE(!inode || !filp))
+		return -EINVAL;
+
+	bao = container_of(inode->i_cdev, struct bao_ipcshmem, cdev);
+	filp->private_data = NULL;
+
+	kobject_put(&bao->dev->kobj);
+
+	return 0;
+}
+
+static const struct file_operations bao_ipcshmem_fops = {
+	.owner = THIS_MODULE,
+	.read = bao_ipcshmem_read_fops,
+	.write = bao_ipcshmem_write_fops,
+	.mmap = bao_ipcshmem_mmap_fops,
+	.open = bao_ipcshmem_open_fops,
+	.release = bao_ipcshmem_release_fops
+};
+
+/**
+ * bao_ipcshmem_register - Register a Bao IPC shared memory device
+ * @pdev: Platform device
+ *
+ * Maps the shared memory region, validates channel layout, initializes
+ * the read/write buffers, registers the character device, and creates
+ * the sysfs device entry.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+static int bao_ipcshmem_register(struct platform_device *pdev)
+{
+	int ret = 0, id = -1;
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct module *owner = THIS_MODULE;
+	struct resource *r;
+	dev_t devt;
+	resource_size_t shmem_size;
+	u32 write_offset, read_offset, write_size, read_size;
+	bool rd_in_range, wr_in_range, disjoint;
+	void *shmem_base_addr = NULL;
+	struct bao_ipcshmem *bao;
+
+	/* Get memory resource */
+	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!r) {
+		dev_err(dev, "failed to get memory resource\n");
+		return -EINVAL;
+	}
+
+	/* Read channel offsets and sizes */
+	of_property_read_u32_index(np, "read-channel", 0, &read_offset);
+	of_property_read_u32_index(np, "read-channel", 1, &read_size);
+	of_property_read_u32_index(np, "write-channel", 0, &write_offset);
+	of_property_read_u32_index(np, "write-channel", 1, &write_size);
+
+	/* Validate memory layout */
+	rd_in_range = (r->start + read_offset + read_size) <= r->end;
+	wr_in_range = (r->start + write_offset + write_size) <= r->end;
+	disjoint = ((read_offset + read_size) <= write_offset) ||
+		   ((write_offset + write_size) <= read_offset);
+
+	if (!rd_in_range || !wr_in_range || !disjoint) {
+		dev_err(dev, "invalid channel layout\n");
+		dev_err(dev, "rd_in_range=%d, wr_in_range=%d, disjoint=%d\n",
+			rd_in_range, wr_in_range, disjoint);
+		return -EINVAL;
+	}
+
+	/* Map shared memory */
+	shmem_size = r->end - r->start + 1;
+	shmem_base_addr = memremap(r->start, shmem_size, MEMREMAP_WB);
+	if (!shmem_base_addr) {
+		dev_err(dev, "failed to map shared memory\n");
+		return -ENOMEM;
+	}
+
+	/* Read device ID from device tree */
+	of_property_read_u32(np, "id", &id);
+	if (id >= MAX_DEVICES) {
+		dev_err(dev, "invalid device id %d\n", id);
+		ret = -EINVAL;
+		goto err_unmap;
+	}
+
+	/* Allocate and initialize device structure */
+	bao = devm_kzalloc(dev, sizeof(*bao), GFP_KERNEL);
+	if (!bao) {
+		ret = -ENOMEM;
+		goto err_unmap;
+	}
+
+	snprintf(bao->label, NAME_LEN, "%s%d", DEV_NAME, id);
+	bao->id = id;
+	bao->read_size = read_size;
+	bao->write_size = write_size;
+	bao->read_base = shmem_base_addr + read_offset;
+	bao->write_base = shmem_base_addr + write_offset;
+	bao->physical_base = (void *)r->start;
+	bao->shmem_size = shmem_size;
+
+	cdev_init(&bao->cdev, &bao_ipcshmem_fops);
+	bao->cdev.owner = owner;
+
+	/* Add character device */
+	devt = MKDEV(MAJOR(bao_ipcshmem_devt), id);
+	ret = cdev_add(&bao->cdev, devt, 1);
+	if (ret)
+		goto err_unmap;
+
+	/* Create device node */
+	bao->dev = device_create(cl, dev, devt, bao, bao->label);
+	if (IS_ERR(bao->dev)) {
+		ret = PTR_ERR(bao->dev);
+		goto err_cdev;
+	}
+	dev_set_drvdata(bao->dev, bao);
+
+	return 0;
+
+err_cdev:
+	cdev_del(&bao->cdev);
+err_unmap:
+	memunmap(shmem_base_addr);
+	dev_err(dev, "failed initialization\n");
+	return ret;
+}
+
+/**
+ * bao_ipcshmem_unregister - Unregister a Bao IPC shared memory device
+ * @pdev: Platform device
+ *
+ * Unmaps the shared memory region, destroys the sysfs device, and
+ * deletes the character device.
+ */
+static void bao_ipcshmem_unregister(struct platform_device *pdev)
+{
+	struct bao_ipcshmem *bao;
+	void *shmem_base;
+
+	/* Retrieve the driver data */
+	bao = dev_get_drvdata(&pdev->dev);
+	if (!bao)
+		return;
+
+	/* Unmap shared memory */
+	if (bao->read_base)
+		shmem_base = (void *)((uintptr_t)bao->read_base -
+				      ((uintptr_t)bao->read_base - (uintptr_t)bao->physical_base));
+	else
+		shmem_base = NULL;
+
+	if (shmem_base)
+		memunmap(shmem_base);
+
+	/* Destroy device node */
+	if (bao->dev)
+		device_destroy(cl, bao->cdev.dev);
+
+	/* Delete character device */
+	cdev_del(&bao->cdev);
+}
+
+static const struct of_device_id of_bao_ipcshmem_match[] = {
+	{
+		.compatible = "bao,ipcshmem",
+	},
+	{ /* sentinel */ }
+};
+
+MODULE_DEVICE_TABLE(of, of_bao_ipcshmem_match);
+
+static struct platform_driver bao_ipcshmem_driver = {
+	.probe = bao_ipcshmem_register,
+	.remove = bao_ipcshmem_unregister,
+	.driver = {
+		   .name = DEV_NAME,
+		   .of_match_table = of_bao_ipcshmem_match,
+		    },
+};
+
+/**
+ * bao_ipcshmem_init - Module initialization for Bao IPC shared memory
+ *
+ * Creates a device class, allocates a range of character device numbers,
+ * and registers the platform driver.
+ *
+ * Return: 0 on success, negative error code on failure.
+ */
+static int __init bao_ipcshmem_init(void)
+{
+	int ret;
+
+	/* Create device class */
+	cl = class_create(DEV_NAME);
+	if (IS_ERR(cl)) {
+		ret = PTR_ERR(cl);
+		pr_err("unable to create class %s\n", DEV_NAME);
+		return ret;
+	}
+
+	/* Allocate major/minor numbers for character devices */
+	ret = alloc_chrdev_region(&bao_ipcshmem_devt, 0, MAX_DEVICES, DEV_NAME);
+	if (ret) {
+		pr_err("unable to allocate chrdev region for %s\n", DEV_NAME);
+		goto err_class_destroy;
+	}
+
+	/* Register platform driver */
+	ret = platform_driver_register(&bao_ipcshmem_driver);
+	if (ret) {
+		pr_err("unable to register platform driver for %s\n", DEV_NAME);
+		goto err_unregister_chrdev;
+	}
+
+	return 0;
+
+err_unregister_chrdev:
+	unregister_chrdev_region(bao_ipcshmem_devt, MAX_DEVICES);
+err_class_destroy:
+	class_destroy(cl);
+	return ret;
+}
+
+/**
+ * bao_ipcshmem_exit - Module exit for Bao IPC shared memory
+ *
+ * Unregisters the platform driver, releases the character device region,
+ * and destroys the device class.
+ */
+static void __exit bao_ipcshmem_exit(void)
+{
+	/* Unregister the platform driver */
+	platform_driver_unregister(&bao_ipcshmem_driver);
+
+	/* Release the allocated character device numbers */
+	unregister_chrdev_region(bao_ipcshmem_devt, MAX_DEVICES);
+
+	/* Destroy the device class */
+	class_destroy(cl);
+}
+
+module_init(bao_ipcshmem_init);
+module_exit(bao_ipcshmem_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("David Cerdeira <davidmcerdeira@osyx.tech>");
+MODULE_AUTHOR("José Martins <jose@osyx.tech>");
+MODULE_AUTHOR("João Peixoto <joaopeixoto@osyx.tech>");
+MODULE_DESCRIPTION("Bao Hypervisor IPC Through Shared-memory Driver");
-- 
2.43.0

[PATCH 3/5] dt-bindings: Add Bao I/O dispatcher driver binding

[joaopeixoto]

From: João Peixoto <joaopeixoto@osyx.tech>

This patch adds a Device Tree binding for the Bao I/O Dispatcher kernel
module, which can be loaded into backend VMs. The I/O Dispatcher
provides the bridge between the Bao hypervisor Remote I/O system and the
frontend device model in userspace, offering a unified API to support
various VirtIO backends.

The dispatcher handles hypercalls to the Bao hypervisor, IRQ/eventfd
forwarding, and provides a character device interface for frontend
devices, enabling efficient communication between the hypervisor and
userspace device models.

The binding documents the following properties:
  - compatible: "bao,io-dispatcher"
  - reg: Memory regions for the dispatcher (multiple VirtIO devices)
  - interrupts: Interrupts used by the devices
  - interrupt-parent: Parent interrupt controller

This enables kernel drivers to correctly instantiate and configure Bao
I/O Dispatcher modules based on the DT description.

Signed-off-by: João Peixoto <joaopeixoto@osyx.tech>
---
 .../bindings/bao/io-dispatcher.yaml           | 67 +++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/bao/io-dispatcher.yaml

diff --git a/Documentation/devicetree/bindings/bao/io-dispatcher.yaml b/Documentation/devicetree/bindings/bao/io-dispatcher.yaml
new file mode 100644
index 000000000000..7795f55d3ff9
--- /dev/null
+++ b/Documentation/devicetree/bindings/bao/io-dispatcher.yaml
@@ -0,0 +1,67 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/bao/io-dispatcher.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: Bao I/O Dispatcher Device
+
+maintainers:
+  - João Peixoto <joaopeixoto@osyx.tech>
+  - José Martins <jose@osyx.tech>
+  - David Cerdeira <davidmcerdeira@osyx.tech>
+
+description: |
+  I/O Dispatcher device for Bao hypervisor guests. Handles multiple VirtIO
+  backend devices and their interrupts.
+
+properties:
+  compatible:
+    const: "bao,io-dispatcher"
+    description: Device compatible string.
+
+  reg:
+    description: |
+      Memory regions for each VirtIO backend device.
+    maxItems: 20
+    type: array
+    items:
+      type: integer
+
+  interrupts:
+    description: |
+      Interrupt numbers for each VirtIO backend device.
+    type: array
+    items:
+      type: integer
+    minItems: 3
+    maxItems: 3
+
+  interrupt-parent:
+    description: Parent interrupt controller node
+    type: string
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - interrupt-parent
+
+additionalProperties: false
+
+examples:
+  - |
+    bao_io_dispatcher: bao-io-dispatcher {
+        compatible = "bao,io-dispatcher";
+        reg = <0x0 0x50000000 0x0 0x01000000
+               0x0 0x51000000 0x0 0x01000000
+               0x0 0x52000000 0x0 0x01000000
+               0x0 0x53000000 0x0 0x01000000
+               0x0 0x54000000 0x0 0x01000000>;
+        interrupts = <0x0 0x08 0x1
+                      0x0 0x09 0x1
+                      0x0 0x0a 0x1
+                      0x0 0x0b 0x1
+                      0x0 0x0c 0x1>;
+        interrupt-parent = <&gic>;
+    };
-- 
2.43.0

[PATCH 5/5] MAINTAINERS: Add entries for Bao hypervisor drivers, headers, and DT bindings

[joaopeixoto]

From: João Peixoto <joaopeixoto@osyx.tech>

Add MAINTAINERS entries for the Bao hypervisor components including:
- Bao IPC shared memory driver and its device tree bindings
- Bao I/O dispatcher driver and its device tree bindings
- Kernel headers for Bao (ARM, ARM64, and RISC-V)
- UAPI header

This ensures that the kernel review and notification system correctly
identifies the maintainers for all Bao hypervisor components in the
kernel tree.

Signed-off-by: João Peixoto <joaopeixoto@osyx.tech>
---
 MAINTAINERS | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index dc731d37c8fe..e50ad6a1bc4a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4321,6 +4321,18 @@ F:	drivers/video/backlight/
 F:	include/linux/backlight.h
 F:	include/linux/pwm_backlight.h
 
+BAO HYPERVISOR
+M:	José Martins <jose@osyx.tech>
+M:	David Cerdeira <davidmcerdeira@osyx.tech>
+M:	João Peixoto <joaopeixoto@osyx.tech>
+S:	Maintained
+F:	Documentation/devicetree/bindings/bao/
+F:	arch/arm/include/asm/bao.h
+F:	arch/arm64/include/asm/bao.h
+F:	arch/riscv/include/asm/bao.h
+F:	drivers/virt/bao
+F:	include/uapi/linux/bao.h
+
 BARCO P50 GPIO DRIVER
 M:	Santosh Kumar Yadav <santoshkumar.yadav@barco.com>
 M:	Peter Korsgaard <peter.korsgaard@barco.com>
-- 
2.43.0

Re: [PATCH 2/5] virt: add Bao IPC shared memory driver

[Greg KH]

On Wed, Dec 24, 2025 at 01:52:14PM +0000, joaopeixoto@osyx.tech wrote:
> From: João Peixoto <joaopeixoto@osyx.tech>
> 
> Add a new driver providing an interface for communication with guests
> hosted by the Bao hypervisor using shared-memory channels. The driver
> exposes read/write regions defined in device tree and notifies the
> hypervisor via an architecture-specific hypercall (SMC/HVC on ARM and
> SBI ecall on RISC-V).
> 
> The patch introduces:
>   - drivers/bao/ with the initial Bao IPC shared-memory implementation
>   - Kconfig entry enabling BAO_SHMEM
>   - Makefile integration for building the driver
>   - A character device interface supporting mmap(), read(), and write()
>   - Platform driver support using DT properties for channel layout
> 
> Each device instance maps its assigned shared-memory region, validates
> read/write channel configuration, and exposes a /dev/baoipc<N> node
> used by user space to exchange data with Bao guests.
> 
> Signed-off-by: João Peixoto <joaopeixoto@osyx.tech>
> ---
>  drivers/virt/Kconfig                 |   2 +
>  drivers/virt/Makefile                |   1 +
>  drivers/virt/bao/Kconfig             |   3 +
>  drivers/virt/bao/Makefile            |   3 +
>  drivers/virt/bao/ipcshmem/Kconfig    |   9 +
>  drivers/virt/bao/ipcshmem/Makefile   |   3 +
>  drivers/virt/bao/ipcshmem/ipcshmem.c | 539 +++++++++++++++++++++++++++

Why two subdirs deep for a single .c file?  Why not just put this in
drivers/virt/ instead?

thanks,

greg k-h

Re: [PATCH 2/5] virt: add Bao IPC shared memory driver

[Greg KH]

On Wed, Dec 24, 2025 at 01:52:14PM +0000, joaopeixoto@osyx.tech wrote:
> +struct class *cl;

Why not just use the misc device api instead?  No need for a full class
for just one char device, right?  Or even if you have multiple ones,
again, no need for a whole class.  That should make the code much
simpler overall.

thanks,

greg k-h

Re: [PATCH 3/5] dt-bindings: Add Bao I/O dispatcher driver binding

[Rob Herring (Arm)]

On Wed, 24 Dec 2025 13:52:15 +0000, joaopeixoto@osyx.tech wrote:
> From: João Peixoto <joaopeixoto@osyx.tech>
> 
> This patch adds a Device Tree binding for the Bao I/O Dispatcher kernel
> module, which can be loaded into backend VMs. The I/O Dispatcher
> provides the bridge between the Bao hypervisor Remote I/O system and the
> frontend device model in userspace, offering a unified API to support
> various VirtIO backends.
> 
> The dispatcher handles hypercalls to the Bao hypervisor, IRQ/eventfd
> forwarding, and provides a character device interface for frontend
> devices, enabling efficient communication between the hypervisor and
> userspace device models.
> 
> The binding documents the following properties:
>   - compatible: "bao,io-dispatcher"
>   - reg: Memory regions for the dispatcher (multiple VirtIO devices)
>   - interrupts: Interrupts used by the devices
>   - interrupt-parent: Parent interrupt controller
> 
> This enables kernel drivers to correctly instantiate and configure Bao
> I/O Dispatcher modules based on the DT description.
> 
> Signed-off-by: João Peixoto <joaopeixoto@osyx.tech>
> ---
>  .../bindings/bao/io-dispatcher.yaml           | 67 +++++++++++++++++++
>  1 file changed, 67 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/bao/io-dispatcher.yaml
> 

My bot found errors running 'make dt_binding_check' on your patch:

yamllint warnings/errors:
./Documentation/devicetree/bindings/bao/ipcshmem.yaml:4:6: [error] string value is redundantly quoted with any quotes (quoted-strings)
./Documentation/devicetree/bindings/bao/ipcshmem.yaml:5:10: [error] string value is redundantly quoted with any quotes (quoted-strings)
./Documentation/devicetree/bindings/bao/ipcshmem.yaml:17:1: [error] syntax error: found character '\t' that cannot start any token (syntax)
./Documentation/devicetree/bindings/bao/io-dispatcher.yaml:4:6: [error] string value is redundantly quoted with any quotes (quoted-strings)
./Documentation/devicetree/bindings/bao/io-dispatcher.yaml:5:10: [error] string value is redundantly quoted with any quotes (quoted-strings)
./Documentation/devicetree/bindings/bao/io-dispatcher.yaml:20:12: [error] string value is redundantly quoted with any quotes (quoted-strings)

dtschema/dtc warnings/errors:
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/bao/ipcshmem.yaml: ignoring, error parsing file
./Documentation/devicetree/bindings/bao/ipcshmem.yaml:17:1: found a tab character where an indentation space is expected
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/bao/io-dispatcher.yaml: properties:reg: 'anyOf' conditional failed, one must be fixed:
	'type' is not one of ['maxItems', 'description', 'deprecated']
		hint: Only "maxItems" is required for a single entry if there are no constraints defined for the values.
	'items' is not one of ['maxItems', 'description', 'deprecated']
		hint: Only "maxItems" is required for a single entry if there are no constraints defined for the values.
	Additional properties are not allowed ('type' was unexpected)
		hint: Arrays must be described with a combination of minItems/maxItems/items
	'maxItems' is not one of ['description', 'deprecated', 'const', 'enum', 'minimum', 'maximum', 'multipleOf', 'default', '$ref', 'oneOf']
	'type' is not one of ['description', 'deprecated', 'const', 'enum', 'minimum', 'maximum', 'multipleOf', 'default', '$ref', 'oneOf']
	'items' is not one of ['description', 'deprecated', 'const', 'enum', 'minimum', 'maximum', 'multipleOf', 'default', '$ref', 'oneOf']
	/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/bao/io-dispatcher.yaml: properties:reg:items: 'anyOf' conditional failed, one must be fixed:
		'maxItems' is a required property
			hint: Only "maxItems" is required for a single entry if there are no constraints defined for the values.
		'type' is not one of ['maxItems', 'description', 'deprecated']
			hint: Only "maxItems" is required for a single entry if there are no constraints defined for the values.
		Additional properties are not allowed ('type' was unexpected)
			hint: Arrays must be described with a combination of minItems/maxItems/items
		'type' is not one of ['description', 'deprecated', 'const', 'enum', 'minimum', 'maximum', 'multipleOf', 'default', '$ref', 'oneOf']
			hint: "items" can be a list defining each entry or a schema applying to all items. A list has an implicit size. A schema requires minItems/maxItems to define the size.
		hint: cell array properties must define how many entries and what the entries are when there is more than one entry.
		from schema $id: http://devicetree.org/meta-schemas/cell.yaml
	1 was expected
		hint: Only "maxItems" is required for a single entry if there are no constraints defined for the values.
	hint: cell array properties must define how many entries and what the entries are when there is more than one entry.
	from schema $id: http://devicetree.org/meta-schemas/cell.yaml
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/bao/io-dispatcher.yaml: properties:reg:type: 'array' is not one of ['boolean', 'object']
	from schema $id: http://devicetree.org/meta-schemas/core.yaml
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/bao/io-dispatcher.yaml: properties:interrupts:type: 'array' is not one of ['boolean', 'object']
	from schema $id: http://devicetree.org/meta-schemas/core.yaml
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/bao/io-dispatcher.yaml: properties:interrupt-parent:type: 'string' is not one of ['boolean', 'object']
	from schema $id: http://devicetree.org/meta-schemas/core.yaml
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/bao/io-dispatcher.yaml: properties:interrupts: 'anyOf' conditional failed, one must be fixed:
	'type' is not one of ['maxItems', 'description', 'deprecated']
		hint: Only "maxItems" is required for a single entry if there are no constraints defined for the values.
	'items' is not one of ['maxItems', 'description', 'deprecated']
		hint: Only "maxItems" is required for a single entry if there are no constraints defined for the values.
	'minItems' is not one of ['maxItems', 'description', 'deprecated']
		hint: Only "maxItems" is required for a single entry if there are no constraints defined for the values.
	Additional properties are not allowed ('type' was unexpected)
		hint: Arrays must be described with a combination of minItems/maxItems/items
	'type' is not one of ['description', 'deprecated', 'const', 'enum', 'minimum', 'maximum', 'multipleOf', 'default', '$ref', 'oneOf']
	'items' is not one of ['description', 'deprecated', 'const', 'enum', 'minimum', 'maximum', 'multipleOf', 'default', '$ref', 'oneOf']
	'minItems' is not one of ['description', 'deprecated', 'const', 'enum', 'minimum', 'maximum', 'multipleOf', 'default', '$ref', 'oneOf']
	'maxItems' is not one of ['description', 'deprecated', 'const', 'enum', 'minimum', 'maximum', 'multipleOf', 'default', '$ref', 'oneOf']
	/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/bao/io-dispatcher.yaml: properties:interrupts:items: 'anyOf' conditional failed, one must be fixed:
		'maxItems' is a required property
			hint: Only "maxItems" is required for a single entry if there are no constraints defined for the values.
		'type' is not one of ['maxItems', 'description', 'deprecated']
			hint: Only "maxItems" is required for a single entry if there are no constraints defined for the values.
		Additional properties are not allowed ('type' was unexpected)
			hint: Arrays must be described with a combination of minItems/maxItems/items
		'type' is not one of ['description', 'deprecated', 'const', 'enum', 'minimum', 'maximum', 'multipleOf', 'default', '$ref', 'oneOf']
			hint: "items" can be a list defining each entry or a schema applying to all items. A list has an implicit size. A schema requires minItems/maxItems to define the size.
		hint: cell array properties must define how many entries and what the entries are when there is more than one entry.
		from schema $id: http://devicetree.org/meta-schemas/cell.yaml
	1 was expected
		hint: Only "maxItems" is required for a single entry if there are no constraints defined for the values.
	hint: cell array properties must define how many entries and what the entries are when there is more than one entry.
	from schema $id: http://devicetree.org/meta-schemas/cell.yaml
/builds/robherring/dt-review-ci/linux/Documentation/devicetree/bindings/bao/io-dispatcher.yaml: properties: False schema does not allow {'description': 'Parent interrupt controller node', 'type': 'string'}
	from schema $id: http://devicetree.org/meta-schemas/interrupts.yaml
make[2]: *** Deleting file 'Documentation/devicetree/bindings/bao/ipcshmem.example.dts'
Documentation/devicetree/bindings/bao/ipcshmem.yaml:17:1: found a tab character where an indentation space is expected
make[2]: *** [Documentation/devicetree/bindings/Makefile:26: Documentation/devicetree/bindings/bao/ipcshmem.example.dts] Error 1
make[2]: *** Waiting for unfinished jobs....
make[1]: *** [/builds/robherring/dt-review-ci/linux/Makefile:1565: dt_binding_check] Error 2
make: *** [Makefile:248: __sub-make] Error 2

doc reference errors (make refcheckdocs):

See https://patchwork.kernel.org/project/devicetree/patch/20251224135217.25350-4-joaopeixoto@osyx.tech

The base for the series is generally the latest rc1. A different dependency
should be noted in *this* patch.

If you already ran 'make dt_binding_check' and didn't see the above
error(s), then make sure 'yamllint' is installed and dt-schema is up to
date:

pip3 install dtschema --upgrade

Please check and re-submit after running the above command yourself. Note
that DT_SCHEMA_FILES can be set to your schema file to speed up checking
your schema. However, it must be unset to test all examples with your schema.

Re: [PATCH 1/5] dt-bindings: Add Bao IPC shared memory driver binding

[Rob Herring (Arm)]

On Wed, 24 Dec 2025 13:52:13 +0000, joaopeixoto@osyx.tech wrote:
> From: João Peixoto <joaopeixoto@osyx.tech>
> 
> This patch adds a Device Tree binding for the Bao IPC shared memory
> device, which provides a standardized description of the hardware
> interface used for inter-VM communication in Bao-based systems.
> 
> The binding documents the following properties:
> 
>   - compatible: "bao,ipcshmem"
>   - reg: Memory region for the shared memory device
>   - id: Unique device identifier
>   - read-channel: [offset, size] for reading from the shared memory
>   - write-channel: [offset, size] for writing to the shared memory
>   - interrupts: Interrupts used by the device
> 
> This enables kernel drivers and userspace tools to correctly
> instantiate and configure Bao IPC shared memory devices based
> on the DT description, facilitating efficient communication
> between VMs.
> 
> Signed-off-by: João Peixoto <joaopeixoto@osyx.tech>
> ---
>  .../devicetree/bindings/bao/ipcshmem.yaml     | 99 +++++++++++++++++++
>  .../devicetree/bindings/vendor-prefixes.yaml  |  2 +
>  2 files changed, 101 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/bao/ipcshmem.yaml
> 

My bot found errors running 'make dt_binding_check' on your patch:

yamllint warnings/errors:

dtschema/dtc warnings/errors:


doc reference errors (make refcheckdocs):

See https://patchwork.kernel.org/project/devicetree/patch/20251224135217.25350-2-joaopeixoto@osyx.tech

The base for the series is generally the latest rc1. A different dependency
should be noted in *this* patch.

If you already ran 'make dt_binding_check' and didn't see the above
error(s), then make sure 'yamllint' is installed and dt-schema is up to
date:

pip3 install dtschema --upgrade

Please check and re-submit after running the above command yourself. Note
that DT_SCHEMA_FILES can be set to your schema file to speed up checking
your schema. However, it must be unset to test all examples with your schema.

Re: [PATCH 0/5] virt: Add Bao hypervisor IPC and I/O dispatcher drivers

[Krzysztof Kozlowski]

On 24/12/2025 14:52, joaopeixoto@osyx.tech wrote:
> From: João Peixoto <joaopeixoto@osyx.tech>
> 
> This series introduces support for the Bao hypervisor guest-side drivers
> under drivers/virt/bao and the associated Device Tree bindings, UAPI,
> and MAINTAINERS entries.
> 
> Bao is a lightweight static-partitioning hypervisor for embedded and
> safety-critical systems. This series adds:
> - The Bao IPC shared memory driver, which enables Linux guests to
>   communicate with each other through shared memory regions.
> - The Bao I/O Dispatcher driver, which allows Bao's VMs to share I/O
>   devices using device paravirtualization (VirtIO).
> 


None of these patches, except MAINTAINERS reached my mailbox. Fix your
submission process, so it will not be marked by spam and bounced.

Best regards,
Krzysztof

Re: [PATCH 5/5] MAINTAINERS: Add entries for Bao hypervisor drivers, headers, and DT bindings

[Krzysztof Kozlowski]

On 24/12/2025 14:52, joaopeixoto@osyx.tech wrote:
> From: João Peixoto <joaopeixoto@osyx.tech>
> 
> Add MAINTAINERS entries for the Bao hypervisor components including:
> - Bao IPC shared memory driver and its device tree bindings
> - Bao I/O dispatcher driver and its device tree bindings
> - Kernel headers for Bao (ARM, ARM64, and RISC-V)
> - UAPI header

This is irrelevant.

> 
> This ensures that the kernel review and notification system correctly
> identifies the maintainers for all Bao hypervisor components in the
> kernel tree.


This is irrelevant as well. Write concise yet useful commit msgs.

Best regards,
Krzysztof

Re: [PATCH 1/5] dt-bindings: Add Bao IPC shared memory driver binding

[Krzysztof Kozlowski]

On Wed, Dec 24, 2025 at 01:52:13PM +0000, joaopeixoto@osyx.tech wrote:
> From: João Peixoto <joaopeixoto@osyx.tech>
> 
> This patch adds a Device Tree binding for the Bao IPC shared memory
> device, which provides a standardized description of the hardware
> interface used for inter-VM communication in Bao-based systems.
> 

All you emails bounced as spam, so you need tofix your email setup. I
found this only via lore.

> The binding documents the following properties:
> 
>   - compatible: "bao,ipcshmem"
>   - reg: Memory region for the shared memory device
>   - id: Unique device identifier
>   - read-channel: [offset, size] for reading from the shared memory
>   - write-channel: [offset, size] for writing to the shared memory
>   - interrupts: Interrupts used by the device

Irrelevant. Drop.

> 
> This enables kernel drivers and userspace tools to correctly
> instantiate and configure Bao IPC shared memory devices based
> on the DT description, facilitating efficient communication
> between VMs.
> 

Irrelevant. Describe hardware.

> Signed-off-by: João Peixoto <joaopeixoto@osyx.tech>
> ---
>  .../devicetree/bindings/bao/ipcshmem.yaml     | 99 +++++++++++++++++++
>  .../devicetree/bindings/vendor-prefixes.yaml  |  2 +
>  2 files changed, 101 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/bao/ipcshmem.yaml


Filename matching compatible.
> 
> diff --git a/Documentation/devicetree/bindings/bao/ipcshmem.yaml b/Documentation/devicetree/bindings/bao/ipcshmem.yaml
> new file mode 100644
> index 000000000000..398ac610c29f
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/bao/ipcshmem.yaml
> @@ -0,0 +1,99 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: "http://devicetree.org/schemas/bao/ipcshmem.yaml#"
> +$schema: "http://devicetree.org/meta-schemas/core.yaml#"
> +
> +title: Bao IPC Shared Memory Device
> +
> +maintainers:
> +  - José Martins <jose@osyx.tech>
> +  - David Cerdeira <davidmcerdeira@osyx.tech>
> +  - João Peixoto <joaopeixoto@osyx.tech>
> +
> +description: |
> +  Shared memory based communication device for Bao hypervisor guests.
> +  It allows the kernel to interface with guests running under
> +	the Bao hypervisor, providing a character device interface
> +	for exchanging data through dedicated shared-memory regions.
> +
> +properties:
> +  compatible:
> +    const: "bao,ipcshmem"
> +
> +  reg:
> +    description: |
> +      Memory resource for the shared memory device.
> +    maxItems: 4
> +    type: array
> +    items:
> +      type: integer


Don't send us LLM junk. Nothing here is even close to proper bindings,
which means:

1. You did not write it yourself, because it is impossible to come with
syntax like that (just does not exist),

2. Did not even bother to test it.


Best regards,
Krzysztof

Re: [PATCH 3/5] dt-bindings: Add Bao I/O dispatcher driver binding

[Krzysztof Kozlowski]

On Wed, Dec 24, 2025 at 01:52:15PM +0000, joaopeixoto@osyx.tech wrote:
> From: João Peixoto <joaopeixoto@osyx.tech>
> 
> This patch adds a Device Tree binding for the Bao I/O Dispatcher kernel
> module, which can be loaded into backend VMs. The I/O Dispatcher
> provides the bridge between the Bao hypervisor Remote I/O system and the
> frontend device model in userspace, offering a unified API to support
> various VirtIO backends.
> 
> The dispatcher handles hypercalls to the Bao hypervisor, IRQ/eventfd
> forwarding, and provides a character device interface for frontend
> devices, enabling efficient communication between the hypervisor and
> userspace device models.
> 
> The binding documents the following properties:
>   - compatible: "bao,io-dispatcher"
>   - reg: Memory regions for the dispatcher (multiple VirtIO devices)
>   - interrupts: Interrupts used by the devices
>   - interrupt-parent: Parent interrupt controller
> 
> This enables kernel drivers to correctly instantiate and configure Bao
> I/O Dispatcher modules based on the DT description.
> 
> Signed-off-by: João Peixoto <joaopeixoto@osyx.tech>
> ---
>  .../bindings/bao/io-dispatcher.yaml           | 67 +++++++++++++++++++
>  1 file changed, 67 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/bao/io-dispatcher.yaml
> 
> diff --git a/Documentation/devicetree/bindings/bao/io-dispatcher.yaml b/Documentation/devicetree/bindings/bao/io-dispatcher.yaml
> new file mode 100644
> index 000000000000..7795f55d3ff9
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/bao/io-dispatcher.yaml
> @@ -0,0 +1,67 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: "http://devicetree.org/schemas/bao/io-dispatcher.yaml#"

You did not even bother to test it.

> +$schema: "http://devicetree.org/meta-schemas/core.yaml#"
> +
> +title: Bao I/O Dispatcher Device
> +
> +maintainers:
> +  - João Peixoto <joaopeixoto@osyx.tech>
> +  - José Martins <jose@osyx.tech>
> +  - David Cerdeira <davidmcerdeira@osyx.tech>
> +
> +description: |
> +  I/O Dispatcher device for Bao hypervisor guests. Handles multiple VirtIO
> +  backend devices and their interrupts.
> +
> +properties:
> +  compatible:
> +    const: "bao,io-dispatcher"
> +    description: Device compatible string.
> +
> +  reg:
> +    description: |
> +      Memory regions for each VirtIO backend device.
> +    maxItems: 20
> +    type: array
> +    items:
> +      type: integer

Don't send us LLM junk. You cannot come with such syntax, it does
not exist. Sending such LLM output is disregard to our time.

NAK


Best regards,
Krzysztof

Re: [PATCH 2/5] virt: add Bao IPC shared memory driver

[Krzysztof Kozlowski]

On Wed, Dec 24, 2025 at 01:52:14PM +0000, joaopeixoto@osyx.tech wrote:
> From: João Peixoto <joaopeixoto@osyx.tech>
> 
> Add a new driver providing an interface for communication with guests
> hosted by the Bao hypervisor using shared-memory channels. The driver
> exposes read/write regions defined in device tree and notifies the
> hypervisor via an architecture-specific hypercall (SMC/HVC on ARM and
> SBI ecall on RISC-V).
> 
> The patch introduces:
>   - drivers/bao/ with the initial Bao IPC shared-memory implementation
>   - Kconfig entry enabling BAO_SHMEM
>   - Makefile integration for building the driver
>   - A character device interface supporting mmap(), read(), and write()
>   - Platform driver support using DT properties for channel layout
> 
> Each device instance maps its assigned shared-memory region, validates
> read/write channel configuration, and exposes a /dev/baoipc<N> node
> used by user space to exchange data with Bao guests.
> 
> Signed-off-by: João Peixoto <joaopeixoto@osyx.tech>
> ---
>  drivers/virt/Kconfig                 |   2 +
>  drivers/virt/Makefile                |   1 +
>  drivers/virt/bao/Kconfig             |   3 +
>  drivers/virt/bao/Makefile            |   3 +
>  drivers/virt/bao/ipcshmem/Kconfig    |   9 +
>  drivers/virt/bao/ipcshmem/Makefile   |   3 +
>  drivers/virt/bao/ipcshmem/ipcshmem.c | 539 +++++++++++++++++++++++++++
>  7 files changed, 560 insertions(+)
>  create mode 100644 drivers/virt/bao/Kconfig
>  create mode 100644 drivers/virt/bao/Makefile
>  create mode 100644 drivers/virt/bao/ipcshmem/Kconfig
>  create mode 100644 drivers/virt/bao/ipcshmem/Makefile
>  create mode 100644 drivers/virt/bao/ipcshmem/ipcshmem.c
> 
> diff --git a/drivers/virt/Kconfig b/drivers/virt/Kconfig
> index 52eb7e4ba71f..cb98c4c52fd1 100644
> --- a/drivers/virt/Kconfig
> +++ b/drivers/virt/Kconfig
> @@ -47,6 +47,8 @@ source "drivers/virt/nitro_enclaves/Kconfig"
>  
>  source "drivers/virt/acrn/Kconfig"
>  
> +source "drivers/virt/bao/Kconfig"
> +
>  endif
>  
>  source "drivers/virt/coco/Kconfig"
> diff --git a/drivers/virt/Makefile b/drivers/virt/Makefile
> index f29901bd7820..623a671f8711 100644
> --- a/drivers/virt/Makefile
> +++ b/drivers/virt/Makefile
> @@ -10,3 +10,4 @@ obj-y				+= vboxguest/
>  obj-$(CONFIG_NITRO_ENCLAVES)	+= nitro_enclaves/
>  obj-$(CONFIG_ACRN_HSM)		+= acrn/
>  obj-y				+= coco/
> +obj-$(CONFIG_BAO_SHMEM)		+= bao/
> diff --git a/drivers/virt/bao/Kconfig b/drivers/virt/bao/Kconfig
> new file mode 100644
> index 000000000000..4f7929d57475
> --- /dev/null
> +++ b/drivers/virt/bao/Kconfig
> @@ -0,0 +1,3 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> +source "drivers/virt/bao/ipcshmem/Kconfig"
> diff --git a/drivers/virt/bao/Makefile b/drivers/virt/bao/Makefile
> new file mode 100644
> index 000000000000..68f5d3f282c4
> --- /dev/null
> +++ b/drivers/virt/bao/Makefile
> @@ -0,0 +1,3 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> +obj-$(CONFIG_BAO_SHMEM) += ipcshmem/
> diff --git a/drivers/virt/bao/ipcshmem/Kconfig b/drivers/virt/bao/ipcshmem/Kconfig
> new file mode 100644
> index 000000000000..42690073e819
> --- /dev/null
> +++ b/drivers/virt/bao/ipcshmem/Kconfig
> @@ -0,0 +1,9 @@
> +# SPDX-License-Identifier: GPL-2.0
> +config BAO_SHMEM
> +	tristate "Bao hypervisor shared memory support"
> +
> +	help
> +	This enables support for Bao shared memory communication.
> +	It allows the kernel to interface with guests running under
> +	the Bao hypervisor, providing a character device interface
> +	for exchanging data through dedicated shared-memory regions.
> diff --git a/drivers/virt/bao/ipcshmem/Makefile b/drivers/virt/bao/ipcshmem/Makefile
> new file mode 100644
> index 000000000000..e027dcdb06aa
> --- /dev/null
> +++ b/drivers/virt/bao/ipcshmem/Makefile
> @@ -0,0 +1,3 @@
> +# SPDX-License-Identifier: GPL-2.0
> +obj-$(CONFIG_BAO_SHMEM) += bao.o
> +bao-objs += ipcshmem.o
> diff --git a/drivers/virt/bao/ipcshmem/ipcshmem.c b/drivers/virt/bao/ipcshmem/ipcshmem.c
> new file mode 100644
> index 000000000000..cadb79bfca6e
> --- /dev/null
> +++ b/drivers/virt/bao/ipcshmem/ipcshmem.c
> @@ -0,0 +1,539 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Bao Hypervisor IPC Through Shared-memory Driver
> + *
> + * Copyright (c) Bao Project and Contributors. All rights reserved.
> + *
> + * Authors:
> + *	David Cerdeira <davidmcerdeira@osyx.tech>
> + *	José Martins <jose@osyx.tech>
> + *	João Peixoto <joaopeixoto@osyx.tech>
> + */
> +
> +#include <linux/types.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/uaccess.h>
> +#include <linux/fs.h>
> +#include <linux/io.h>
> +#include <linux/ioport.h>
> +#include <linux/interrupt.h>
> +#include <linux/of.h>
> +#include <linux/io.h>
> +#include <linux/mutex.h>
> +#include <linux/poll.h>
> +#include <linux/platform_device.h>
> +#include <linux/ioctl.h>
> +#include <linux/cdev.h>
> +#include <linux/device.h>
> +#include <linux/spinlock.h>
> +#include <linux/mutex.h>
> +#include <linux/wait.h>
> +#include <linux/mm.h>
> +
> +#if defined(CONFIG_ARM64) || defined(CONFIG_ARM)
> +#include <linux/arm-smccc.h>
> +#include <asm/memory.h>
> +#elif CONFIG_RISCV
> +#include <asm/sbi.h>
> +#endif
> +
> +#define DEV_NAME "baoipc"
> +#define MAX_DEVICES 16
> +#define NAME_LEN 32
> +
> +static dev_t bao_ipcshmem_devt;
> +struct class *cl;
> +
> +/**
> + * struct bao_ipcshmem - Bao IPC shared memory device
> + * @cdev: Character device interface
> + * @dev: Device structure
> + * @id: Device instance ID
> + * @label: Name/label of the device
> + * @read_base: Base address of the read channel
> + * @read_size: Size of the read channel
> + * @write_base: Base address of the write channel
> + * @write_size: Size of the write channel
> + * @physical_base: Physical memory base address
> + * @shmem_size: Total size of the shared memory region
> + */
> +struct bao_ipcshmem {
> +	struct cdev cdev;
> +	struct device *dev;
> +	int id;
> +	char label[NAME_LEN];
> +	void *read_base;
> +	size_t read_size;
> +	void *write_base;
> +	size_t write_size;
> +	phys_addr_t *physical_base;
> +	size_t shmem_size;
> +};
> +
> +#ifdef CONFIG_ARM64

No ifdefs. Read Linux coding style first.

> +/**
> + * bao_ipcshmem_notify - Notify the Bao hypervisor of an IPC shared memory event (ARM64)
> + * @dev: IPC shared memory device
> + *
> + * Executes a fast SMC hypercall to notify the hypervisor of an event
> + * associated with the given IPC shared memory device.
> + *
> + * Return: Hypercall return value.
> + */
> +static uint64_t bao_ipcshmem_notify(struct bao_ipcshmem *dev)
> +{
> +	register uint64_t x0 asm("x0") =
> +		ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_64,
> +				   ARM_SMCCC_OWNER_VENDOR_HYP, 1);
> +	register uint64_t x1 asm("x1") = dev->id;
> +	register uint64_t x2 asm("x2") = 0;
> +
> +	asm volatile("hvc 0\t\n" : "=r"(x0) : "r"(x0), "r"(x1), "r"(x2));
> +
> +	return x0;
> +}
> +#elif CONFIG_ARM
> +/**
> + * bao_ipcshmem_notify - Notify the Bao hypervisor of an IPC shared memory event (ARM)
> + * @dev: IPC shared memory device
> + *
> + * Executes a fast SMC hypercall to notify the hypervisor of an event
> + * associated with the given IPC shared memory device.
> + *
> + * Return: Hypercall return value.
> + */
> +static uint32_t bao_ipcshmem_notify(struct bao_ipcshmem *dev)
> +{
> +	register uint32_t r0 asm("r0") =
> +		ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_32,
> +				   ARM_SMCCC_OWNER_VENDOR_HYP, 1);
> +	register uint32_t r1 asm("r1") = dev->id;
> +	register uint32_t r2 asm("r2") = 0;
> +
> +	asm volatile("hvc #0\t\n" : "=r"(r0) : "r"(r0), "r"(r1), "r"(r2));
> +
> +	return r0;
> +}
> +#elif CONFIG_RISCV
> +/**
> + * bao_ipcshmem_notify - Notify the Bao hypervisor of an IPC shared memory event (RISC-V)
> + * @dev: IPC shared memory device
> + *
> + * Executes an SBI call to notify the Bao hypervisor of an IPC shared memory event.
> + *
> + * Return: SBI call error code.
> + */
> +static uint64_t bao_ipcshmem_notify(struct bao_ipcshmem *dev)
> +{
> +	struct sbiret ret = sbi_ecall(0x08000ba0, 1, dev->id, 0, 0, 0, 0, 0);
> +
> +	return ret.error;
> +}
> +#endif
> +
> +/**
> + * bao_ipcshmem_mmap_fops - mmap handler for IPC shared memory
> + * @filp: File pointer
> + * @vma: Virtual memory area
> + *
> + * Maps the physical shared memory of the Bao IPC device into
> + * userspace using remap_pfn_range.
> + *
> + * Return: 0 on success, -EFAULT on failure.
> + */
> +static int bao_ipcshmem_mmap_fops(struct file *filp, struct vm_area_struct *vma)
> +{
> +	struct bao_ipcshmem *bao = filp->private_data;
> +	unsigned long vsize = vma->vm_end - vma->vm_start;
> +	unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
> +	phys_addr_t paddr;
> +
> +	if (WARN_ON_ONCE(!bao))
> +		return -ENODEV;
> +
> +	if (!vsize)
> +		return -EINVAL;
> +
> +	if (offset >= bao->shmem_size)
> +		return -EINVAL;
> +
> +	if (vsize > bao->shmem_size - offset)
> +		return -EINVAL;
> +
> +	paddr = (phys_addr_t)bao->physical_base + offset;
> +
> +	if (!PAGE_ALIGNED(paddr))
> +		return -EINVAL;
> +
> +	if (remap_pfn_range(vma, vma->vm_start,
> +			    paddr >> PAGE_SHIFT,
> +			    vsize, vma->vm_page_prot))
> +		return -EFAULT;
> +
> +	return 0;
> +}
> +
> +/**
> + * bao_ipcshmem_read_fops - read handler for IPC shared memory
> + * @filp: File pointer
> + * @buf: Userspace buffer
> + * @count: Number of bytes to read
> + * @ppos: File offset
> + *
> + * Copies data from the Bao IPC read buffer to userspace.
> + *
> + * Return: Number of bytes read, or 0 if EOF.
> + */
> +static ssize_t bao_ipcshmem_read_fops(struct file *filp, char __user *buf,
> +				      size_t count, loff_t *ppos)
> +{
> +	struct bao_ipcshmem *bao = filp->private_data;
> +	size_t available;
> +
> +	if (WARN_ON_ONCE(!bao || !buf || !ppos))
> +		return -EINVAL;
> +
> +	if (*ppos >= bao->read_size)
> +		return 0;
> +
> +	available = bao->read_size - *ppos;
> +	if (count > available)
> +		count = available;
> +
> +	if (copy_to_user(buf, bao->read_base + *ppos, count))
> +		return -EFAULT;
> +
> +	*ppos += count;
> +	return count;
> +}
> +
> +/**
> + * bao_ipcshmem_write_fops - write handler for IPC shared memory
> + * @filp: File pointer
> + * @buf: Userspace buffer
> + * @count: Number of bytes to write
> + * @ppos: File offset
> + *
> + * Copies data from userspace to the Bao IPC write buffer and
> + * notifies the hypervisor of the update.
> + *
> + * Return: Number of bytes written.
> + */
> +static ssize_t bao_ipcshmem_write_fops(struct file *filp, const char __user *buf,
> +				       size_t count, loff_t *ppos)
> +{
> +	struct bao_ipcshmem *bao = filp->private_data;
> +	size_t avail;
> +
> +	if (WARN_ON_ONCE(!bao || !buf || !ppos))
> +		return -EINVAL;
> +
> +	if (*ppos >= bao->write_size)
> +		return 0;
> +
> +	avail = bao->write_size - *ppos;
> +	if (count > avail)
> +		count = avail;
> +
> +	if (copy_from_user(bao->write_base + *ppos, buf, count))
> +		return -EFAULT;
> +
> +	*ppos += count;
> +
> +	/* Notify any listeners that new data is available */
> +	bao_ipcshmem_notify(bao);
> +
> +	return count;
> +}
> +
> +/**
> + * bao_ipcshmem_open_fops - open handler for IPC shared memory
> + * @inode: Inode pointer
> + * @filp: File pointer
> + *
> + * Associates the file with the Bao IPC device and increments
> + * the kobject reference.
> + *
> + * Return: 0 on success.
> + */
> +static int bao_ipcshmem_open_fops(struct inode *inode, struct file *filp)
> +{
> +	struct bao_ipcshmem *bao;
> +
> +	if (WARN_ON_ONCE(!inode || !filp))
> +		return -EINVAL;
> +
> +	bao = container_of(inode->i_cdev, struct bao_ipcshmem, cdev);
> +	filp->private_data = bao;
> +
> +	kobject_get(&bao->dev->kobj);
> +
> +	return 0;
> +}
> +
> +/**
> + * bao_ipcshmem_release_fops - release handler for IPC shared memory
> + * @inode: Inode pointer
> + * @filp: File pointer
> + *
> + * Disassociates the file from the Bao IPC device and decrements
> + * the kobject reference.
> + *
> + * Return: 0 on success.
> + */
> +static int bao_ipcshmem_release_fops(struct inode *inode, struct file *filp)
> +{
> +	struct bao_ipcshmem *bao;
> +
> +	if (WARN_ON_ONCE(!inode || !filp))
> +		return -EINVAL;
> +
> +	bao = container_of(inode->i_cdev, struct bao_ipcshmem, cdev);
> +	filp->private_data = NULL;
> +
> +	kobject_put(&bao->dev->kobj);
> +
> +	return 0;
> +}
> +
> +static const struct file_operations bao_ipcshmem_fops = {
> +	.owner = THIS_MODULE,
> +	.read = bao_ipcshmem_read_fops,
> +	.write = bao_ipcshmem_write_fops,
> +	.mmap = bao_ipcshmem_mmap_fops,
> +	.open = bao_ipcshmem_open_fops,
> +	.release = bao_ipcshmem_release_fops
> +};
> +
> +/**
> + * bao_ipcshmem_register - Register a Bao IPC shared memory device
> + * @pdev: Platform device
> + *
> + * Maps the shared memory region, validates channel layout, initializes
> + * the read/write buffers, registers the character device, and creates
> + * the sysfs device entry.
> + *
> + * Return: 0 on success, negative error code on failure.
> + */
> +static int bao_ipcshmem_register(struct platform_device *pdev)

NAK, where did you get it from? Probe functions are ABSOLUTELY NEVER
called register.

> +{
> +	int ret = 0, id = -1;
> +	struct device *dev = &pdev->dev;
> +	struct device_node *np = dev->of_node;
> +	struct module *owner = THIS_MODULE;
> +	struct resource *r;
> +	dev_t devt;

No, read Linux coding style.

> +	resource_size_t shmem_size;
> +	u32 write_offset, read_offset, write_size, read_size;
> +	bool rd_in_range, wr_in_range, disjoint;
> +	void *shmem_base_addr = NULL;
> +	struct bao_ipcshmem *bao;

This is really poor coding style, barely readable and maintainable. You
need to rewtite this driver completely to match what we expect in Linux
kernel, for example base your work on last, reviewed code.

I am not even looking at rest of this - please prove that you value our
time by sending something following Linux kernel style.

Best regards,
Krzysztof

Re: [PATCH 4/5] virt: add Bao I/O dispatcher driver

[Krzysztof Kozlowski]

On Wed, Dec 24, 2025 at 01:52:16PM +0000, joaopeixoto@osyx.tech wrote:
> +static const struct of_device_id bao_io_dispatcher_driver_dt_ids[] = {
> +	{ .compatible = "bao,io-dispatcher" },
> +	{ /* sentinel */ }
> +};
> +
> +MODULE_DEVICE_TABLE(of, bao_io_dispatcher_driver_dt_ids);
> +
> +static struct platform_driver bao_io_dispatcher_driver = {
> +	.probe = bao_io_dispatcher_driver_register,
> +	.remove = bao_io_dispatcher_driver_unregister,
> +	.driver = {
> +		   .name = "bao-io-dispatcher",
> +		   .of_match_table =
> +		   of_match_ptr(bao_io_dispatcher_driver_dt_ids),

You have warnings here. Do extensive building of your code before
sending.

> +		   .owner = THIS_MODULE,

NAK

Don't send us 12-year-old vendor code. Tools already report this,
so you just did not run them...

Nothing here is evn formatted correctly...

Best regards,
Krzysztof