drivers/staging: Gasket driver framework + Apex driver

The Gasket (Google ASIC Software, Kernel Extensions, and Tools) kernel
framework is a generic, flexible system that supports thin kernel
drivers. Gasket kernel drivers are expected to handle opening and
closing devices, mmap'ing BAR space as requested, a small selection of
ioctls, and handling page table translation (covered below). Any other
functions should be handled by userspace code.

The Gasket common module is not enough to run a device. In order to
customize the Gasket code for a given piece of hardware, a device
specific module must be created. At a minimum, this module must define a
struct gasket_driver_desc containing the device-specific data for use by
the framework; in addition, the module must declare an __init function
that calls gasket_register_device with the module's gasket_driver_desc
struct. Finally, the driver must define an exit function that calls
gasket_unregister_device with the module's gasket_driver_desc struct.

One of the core assumptions of the Gasket framework is that precisely
one process is allowed to have an open write handle to the device node
at any given time. (That process may, once it has one write handle, open
any number of additional write handles.) This is accomplished by
tracking open and close data for each driver instance.

Signed-off-by: Rob Springer <rspringer@google.com>
Signed-off-by: John Joseph <jnjoseph@google.com>
Signed-off-by: Simon Que <sque@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 129 insertions, 0 deletions

diff --git a/drivers/staging/gasket/gasket.h b/drivers/staging/gasket/gasket.h
new file mode 100644
index 000000000000..593d50820c65
--- /dev/null
+++ b/drivers/staging/gasket/gasket.h
@@ -0,0 +1,129 @@
+/* Common Gasket device kernel and user space declarations.
+ *
+ * Copyright (C) 2018 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+#ifndef __GASKET_H__
+#define __GASKET_H__
+
+#include <linux/ioctl.h>
+#include <linux/types.h>
+
+/* ioctl structure declarations */
+
+/* Ioctl structures are padded to a multiple of 64 bits */
+/* and padded to put 64 bit values on 64 bit boundaries. */
+/* Unsigned 64 bit integers are used to hold pointers. */
+/* This helps compatibility between 32 and 64 bits. */
+
+/*
+ * Common structure for ioctls associating an eventfd with a device interrupt,
+ * when using the Gasket interrupt module.
+ */
+struct gasket_interrupt_eventfd {
+	u64 interrupt;
+	u64 event_fd;
+};
+
+/*
+ * Common structure for ioctls mapping and unmapping buffers when using the
+ * Gasket page_table module.
+ */
+struct gasket_page_table_ioctl {
+	u64 page_table_index;
+	u64 size;
+	u64 host_address;
+	u64 device_address;
+};
+
+/*
+ * Common structure for ioctls mapping and unmapping buffers when using the
+ * Gasket page_table module.
+ * dma_address: phys addr start of coherent memory, allocated by kernel
+ */
+struct gasket_coherent_alloc_config_ioctl {
+	u64 page_table_index;
+	u64 enable;
+	u64 size;
+	u64 dma_address;
+};
+
+/* Base number for all Gasket-common IOCTLs */
+#define GASKET_IOCTL_BASE 0xDC
+
+/* Reset the device using the specified reset type. */
+#define GASKET_IOCTL_RESET _IOW(GASKET_IOCTL_BASE, 0, unsigned long)
+
+/* Associate the specified [event]fd with the specified interrupt. */
+#define GASKET_IOCTL_SET_EVENTFD                                               \
+	_IOW(GASKET_IOCTL_BASE, 1, struct gasket_interrupt_eventfd)
+
+/*
+ * Clears any eventfd associated with the specified interrupt. The (ulong)
+ * argument is the interrupt number to clear.
+ */
+#define GASKET_IOCTL_CLEAR_EVENTFD _IOW(GASKET_IOCTL_BASE, 2, unsigned long)
+
+/*
+ * [Loopbacks only] Requests that the loopback device send the specified
+ * interrupt to the host. The (ulong) argument is the number of the interrupt to
+ * send.
+ */
+#define GASKET_IOCTL_LOOPBACK_INTERRUPT                                        \
+	_IOW(GASKET_IOCTL_BASE, 3, unsigned long)
+
+/* Queries the kernel for the number of page tables supported by the device. */
+#define GASKET_IOCTL_NUMBER_PAGE_TABLES _IOR(GASKET_IOCTL_BASE, 4, u64)
+
+/*
+ * Queries the kernel for the maximum size of the page table.  Only the size and
+ * page_table_index fields are used from the struct gasket_page_table_ioctl.
+ */
+#define GASKET_IOCTL_PAGE_TABLE_SIZE                                           \
+	_IOWR(GASKET_IOCTL_BASE, 5, struct gasket_page_table_ioctl)
+
+/*
+ * Queries the kernel for the current simple page table size.  Only the size and
+ * page_table_index fields are used from the struct gasket_page_table_ioctl.
+ */
+#define GASKET_IOCTL_SIMPLE_PAGE_TABLE_SIZE                                    \
+	_IOWR(GASKET_IOCTL_BASE, 6, struct gasket_page_table_ioctl)
+
+/*
+ * Tells the kernel to change the split between the number of simple and
+ * extended entries in the given page table. Only the size and page_table_index
+ * fields are used from the struct gasket_page_table_ioctl.
+ */
+#define GASKET_IOCTL_PARTITION_PAGE_TABLE                                      \
+	_IOW(GASKET_IOCTL_BASE, 7, struct gasket_page_table_ioctl)
+
+/*
+ * Tells the kernel to map size bytes at host_address to device_address in
+ * page_table_index page table.
+ */
+#define GASKET_IOCTL_MAP_BUFFER                                                \
+	_IOW(GASKET_IOCTL_BASE, 8, struct gasket_page_table_ioctl)
+
+/*
+ * Tells the kernel to unmap size bytes at host_address from device_address in
+ * page_table_index page table.
+ */
+#define GASKET_IOCTL_UNMAP_BUFFER                                              \
+	_IOW(GASKET_IOCTL_BASE, 9, struct gasket_page_table_ioctl)
+
+/* Clear the interrupt counts stored for this device. */
+#define GASKET_IOCTL_CLEAR_INTERRUPT_COUNTS _IO(GASKET_IOCTL_BASE, 10)
+
+/* Enable/Disable and configure the coherent allocator. */
+#define GASKET_IOCTL_CONFIG_COHERENT_ALLOCATOR                                 \
+	_IOWR(GASKET_IOCTL_BASE, 11, struct gasket_coherent_alloc_config_ioctl)
+
+#endif /* __GASKET_H__ */