/*
* Greybus operations
*
* Copyright 2014 Google Inc.
*
* Released under the GPLv2 only.
*/
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/workqueue.h>
#include "greybus.h"
/*
* The top bit of the type in an operation message header indicates
* whether the message is a request (bit clear) or response (bit set)
*/
#define GB_OPERATION_TYPE_RESPONSE 0x80
#define OPERATION_TIMEOUT_DEFAULT 1000 /* milliseconds */
/*
* XXX This needs to be coordinated with host driver parameters
* XXX May need to reduce to allow for message header within a page
*/
#define GB_OPERATION_MESSAGE_SIZE_MAX 4096
static struct kmem_cache *gb_operation_cache;
/* Workqueue to handle Greybus operation completions. */
static struct workqueue_struct *gb_operation_workqueue;
/* Protects the cookie representing whether a message is in flight */
static DEFINE_MUTEX(gb_message_mutex);
/*
* All operation messages (both requests and responses) begin with
* a header that encodes the size of the data (header included).
* This header also contains a unique identifier, which is used to
* keep track of in-flight operations. The header contains an
* operation type field, whose interpretation is dependent on what
* type of protocol is used over the connection.
*
* The high bit (0x80) of the operation type field is used to
* indicate whether the message is a request (clear) or a response
* (set).
*
* Response messages include an additional status byte, which
* communicates the result of the corresponding request. A zero
* status value means the operation completed successfully. Any
* other value indicates an error; in this case, the payload of the
* response message (if any) is ignored. The status byte must be
* zero in the header for a request message.
*
* The wire format for all numeric fields in the header is little
* endian. Any operation-specific data begins immediately after the
* header, and is 64-bit aligned.
*/
struct gb_operation_msg_hdr {
__le16 size; /* Size in bytes of header + payload */
__le16 operation_id; /* Operation unique id */
__u8 type; /* E.g GB_I2C_TYPE_* or GB_GPIO_TYPE_* */
__u8 result; /* Result of request (in responses only) */
/* 2 bytes pad, must be zero (ignore when read) */
} __aligned(sizeof(u64));
/* XXX Could be per-host device, per-module, or even per-connection */
static DEFINE_SPINLOCK(gb_operations_lock);
/*
* Set an operation's result.
*
* Initially an outgoing operation's errno value is -EBADR.
* If no error occurs before sending the request message the only
* valid value operation->errno can be set to is -EINPROGRESS,
* indicating the request has been (or rather is about to be) sent.
* At that point nobody should be looking at the result until the
* reponse arrives.
*
* The first time the result gets set after the request has been
* sent, that result "sticks." That is, if two concurrent threads
* race to set the result, the first one wins. The return value
* tells the caller whether its result was recorded; if not the
* caller has nothing more to do.
*
* The result value -EILSEQ is reserved to signal an implementation
* error; if it's ever observed, the code performing the request has
* done something fundamentally wrong. It is an error to try to set
* the result to -EBADR, and attempts to do so result in a warning,
* and -EILSEQ is used instead. Similarly, the only valid result
* value to set for an operation in initial state is -EINPROGRESS.
* Attempts to do otherwise will also record a (successful) -EILSEQ
* operation result.
*/
static bool gb_operation_result_set(struct gb_operation *operation, int result)
{
int prev;
if (result == -EINPROGRESS) {
/*
* -EINPROGRESS is used to indicate the request is
* in flight. It should be the first result value
* set after the initial -EBADR. Issue a warning
* and record an implementation error if it's
* set at any other time.
*/
spin_lock_irq(&gb_operations_lock);
prev = operation->errno;
if (prev == -EBADR)
operation->errno = result;
else
operation->errno = -EILSEQ;
spin_unlock_irq(&gb_operations_lock);
WARN_ON(prev != -EBADR);
return true;
}
/*
* The first result value set after a request has been sent
* will be the final result of the operation. Subsequent
* attempts to set the result are ignored.
*
* Note that -EBADR is a reserved "initial state" result
* value. Attempts to set this value result in a warning,
* and the result code is set to -EILSEQ instead.
*/
if (WARN_ON(result == -EBADR))
result = -EILSEQ; /* Nobody should be setting -EBADR */
spin_lock_irq(&gb_operations_lock);
prev = operation->errno;
if (prev == -EINPROGRESS)
operation->errno = result; /* First and final result */
spin_unlock_irq(&gb_operations_lock);
return prev == -EINPROGRESS;
}
int gb_operation_result(struct gb_operation *operation)
{
int result = operation->errno;
WARN_ON(result == -EBADR);
WARN_ON(result == -EINPROGRESS);
return result;
}
static void gb_pending_operation_insert(struct gb_operation *operation)
{
struct gb_connection *connection = operation->connection;
struct gb_operation_msg_hdr *header;
/*
* Assign the operation's id and move it into its
* connection's pending list.
*/
spin_lock_irq(&gb_operations_lock);
operation->id = ++connection->op_cycle;
list_move_tail(&operation->links, &connection->pending);
spin_unlock_irq(&gb_operations_lock);
/* Store the operation id in the request header */
header = operation->request->header;
header->operation_id = cpu_to_le16(operation->id);
}
static void gb_pending_operation_remove(struct gb_operation *operation)
{
struct gb_connection *connection = operation->connection;
/* Take us off of the list of pending operations */
spin_lock_irq(&gb_operations_lock);
list_move_tail(&operation->links, &connection->operations);
spin_unlock_irq(&gb_operations_lock);
}
static struct gb_operation *
gb_pending_operation_find(struct gb_connection *connection, u16 operation_id)
{
struct gb_operation *operation;
bool found = false;
spin_lock_irq(&gb_operations_lock);
list_for_each_entry(operation, &connection->pending, links)
if (operation->id == operation_id) {
found = true;
break;
}
spin_unlock_irq(&gb_operations_lock);
return found ? operation : NULL;
}
static int gb_message_send(struct gb_message *message)
{
struct gb_connection *connection = message->operation->connection;
u16 dest_cport_id = connection->interface_cport_id;
int ret = 0;
void *cookie;
mutex_lock(&gb_message_mutex);
cookie = connection->hd->driver->buffer_send(connection->hd,
dest_cport_id,
message->header,
message->size,
GFP_KERNEL);
if (IS_ERR(cookie))
ret = PTR_ERR(cookie);
else
message->cookie = cookie;
mutex_unlock(&gb_message_mutex);
return ret;
}
/*
* Cancel a message whose buffer we have passed to the host device
* layer to be sent.
*/
static void gb_message_cancel(struct gb_message *message)
{
mutex_lock(&gb_message_mutex);
if (message->cookie) {
struct greybus_host_device *hd;
hd = message->operation->connection->hd;
hd->driver->buffer_cancel(message->cookie);
}
mutex_unlock(&gb_message_mutex);
}
#if 0
static void gb_operation_request_handle(struct gb_operation *operation)
{
struct gb_protocol *protocol = operation->connection->protocol;
struct gb_operation_msg_hdr *header;
header = operation->request->header;
/*
* If the protocol has no incoming request handler, report
* an error and mark the request bad.
*/
if (protocol->request_recv) {
protocol->request_recv(header->type, operation);
return;
}
gb_connection_err(operation->connection,
"unexpected incoming request type 0x%02hhx\n", header->type);
(void)gb_operation_result_set(operation, -EPROTONOSUPPORT);
}
#endif
/*
* Complete an operation in non-atomic context. The operation's
* result value should have been set before queueing this.
*/
static void gb_operation_work(struct work_struct *work)
{
struct gb_operation *operation;
operation = container_of(work, struct gb_operation, work);
if (operation->callback) {
operation->callback(operation);
operation->callback = NULL;
}
gb_operation_put(operation);
}
/*
* Timeout call for the operation.
*/
static void gb_operation_timeout(struct work_struct *work)
{
struct gb_operation *operation;
operation = container_of(work, struct gb_operation, timeout_work.work);
gb_operation_cancel(operation, -ETIMEDOUT);
}
/*
* Given a pointer to the header in a message sent on a given host
* device, return the associated message structure. (This "header"
* is just the buffer pointer we supply to the host device for
* sending.)
*/
static struct gb_message *
gb_hd_message_find(struct greybus_host_device *hd, void *header)
{
struct gb_message *message;
u8 *result;
result = (u8 *)header - hd->buffer_headroom - sizeof(*message);
message = (struct gb_message *)result;
return message;
}
/*
* Allocate a message to be used for an operation request or
* response. For outgoing messages, both types of message contain a
* common header, which is filled in here. Incoming requests or
* responses also contain the same header, but there's no need to
* initialize it here (it'll be overwritten by the incoming
* message).
*
* Our message structure consists of:
* message structure
* headroom
* message header \_ these combined are
* message payload / the message size
*/
static struct gb_message *
gb_operation_message_alloc(struct greybus_host_device *hd, u8 type,
size_t payload_size, gfp_t gfp_flags)
{
struct gb_message *message;
struct gb_operation_msg_hdr *header;
size_t message_size = payload_size + sizeof(*header);
size_t size;
u8 *buffer;
if (hd->buffer_size_max > GB_OPERATION_MESSAGE_SIZE_MAX) {
pr_warn("limiting buffer size to %u\n",
GB_OPERATION_MESSAGE_SIZE_MAX);
hd->buffer_size_max = GB_OPERATION_MESSAGE_SIZE_MAX;
}
if (message_size > hd->buffer_size_max)
return NULL;
size = sizeof(*message) + hd->buffer_headroom + message_size;
message = kzalloc(size, gfp_flags);
if (!message)
return NULL;
buffer = &message->buffer[0];
header = (struct gb_operation_msg_hdr *)(buffer + hd->buffer_headroom);
/* Fill in the header structure */
header->size = cpu_to_le16(message_size);
header->operation_id = 0; /* Filled in when submitted */
header->type = type;
message->header = header;
message->payload = header + 1;
message->size = message_size;
return message;
}
static void gb_operation_message_free(struct gb_message *message)
{
kfree(message);
}
/*
* Map an enum gb_operation_status value (which is represented in a
* message as a single byte) to an appropriate Linux negative errno.
*/
int gb_operation_status_map(u8 status)
{
switch (status) {
case GB_OP_SUCCESS:
return 0;
case GB_OP_INTERRUPTED:
return -EINTR;
case GB_OP_TIMEOUT:
return -ETIMEDOUT;
case GB_OP_NO_MEMORY:
return -ENOMEM;
case GB_OP_PROTOCOL_BAD:
return -EPROTONOSUPPORT;
case GB_OP_OVERFLOW:
return -EMSGSIZE;
case GB_OP_INVALID:
return -EINVAL;
case GB_OP_RETRY:
return -EAGAIN;
case GB_OP_MALFUNCTION:
return -EILSEQ;
case GB_OP_UNKNOWN_ERROR:
default:
return -EIO;
}
}
/*
* Create a Greybus operation to be sent over the given connection.
* The request buffer will be big enough for a payload of the given
* size. Outgoing requests must specify the size of the response
* buffer size, which must be sufficient to hold all expected
* response data.
*
* Incoming requests will supply a response size of 0, and in that
* case no response buffer is allocated. (A response always
* includes a status byte, so 0 is not a valid size.) Whatever
* handles the operation request is responsible for allocating the
* response buffer.
*
* Returns a pointer to the new operation or a null pointer if an
* error occurs.
*/
static struct gb_operation *
gb_operation_create_common(struct gb_connection *connection, bool outgoing,
u8 type, size_t request_size,
size_t response_size)
{
struct greybus_host_device *hd = connection->hd;
struct gb_operation *operation;
gfp_t gfp_flags = outgoing ? GFP_KERNEL : GFP_ATOMIC;
operation = kmem_cache_zalloc(gb_operation_cache, gfp_flags);
if (!operation)
return NULL;
operation->connection = connection;
operation->request = gb_operation_message_alloc(hd, type, request_size,
gfp_flags);
if (!operation->request)
goto err_cache;
operation->request->operation = operation;
if (outgoing) {
type |= GB_OPERATION_TYPE_RESPONSE;
operation->response = gb_operation_message_alloc(hd, type,
response_size, GFP_KERNEL);
if (!operation->response)
goto err_request;
operation->response->operation = operation;
}
operation->errno = -EBADR; /* Initial value--means "never set" */
INIT_WORK(&operation->work, gb_operation_work);
operation->callback = NULL; /* set at submit time */
init_completion(&operation->completion);
INIT_DELAYED_WORK(&operation->timeout_work, gb_operation_timeout);
kref_init(&operation->kref);
spin_lock_irq(&gb_operations_lock);
list_add_tail(&operation->links, &connection->operations);
spin_unlock_irq(&gb_operations_lock);
return operation;
err_request:
gb_operation_message_free(operation->request);
err_cache:
kmem_cache_free(gb_operation_cache, operation);
return NULL;
}
struct gb_operation *gb_operation_create(struct gb_connection *connection,
u8 type, size_t request_size,
size_t response_size)
{
return gb_operation_create_common(connection, true, type,
request_size, response_size);
}
static struct gb_operation *
gb_operation_create_incoming(struct gb_connection *connection,
u16 operation_id, u8 type,
void *data, size_t request_size)
{
struct gb_operation *operation;
operation = gb_operation_create_common(connection, false, type,
request_size, 0);
if (operation) {
operation->id = operation_id;
memcpy(operation->request->header, data, request_size);
}
return operation;
}
/*
* Get an additional reference on an operation.
*/
void gb_operation_get(struct gb_operation *operation)
{
kref_get(&operation->kref);
}
/*
* Destroy a previously created operation.
*/
static void _gb_operation_destroy(struct kref *kref)
{
struct gb_operation *operation;
operation = container_of(kref, struct gb_operation, kref);
/* XXX Make sure it's not in flight */
spin_lock_irq(&gb_operations_lock);
list_del(&operation->links);
spin_unlock_irq(&gb_operations_lock);
gb_operation_message_free(operation->response);
gb_operation_message_free(operation->request);
kmem_cache_free(gb_operation_cache, operation);
}
/*
* Drop a reference on an operation, and destroy it when the last
* one is gone.
*/
void gb_operation_put(struct gb_operation *operation)
{
if (!WARN_ON(!operation))
kref_put(&operation->kref, _gb_operation_destroy);
}
/* Tell the requester we're done */
static void gb_operation_sync_callback(struct gb_operation *operation)
{
complete(&operation->completion);
}
/*
* Send an operation request message. The caller has filled in
* any payload so the request message is ready to go. If non-null,
* the callback function supplied will be called when the response
* message has arrived indicating the operation is complete. In
* that case, the callback function is responsible for fetching the
* result of the operation using gb_operation_result() if desired,
* and dropping the final reference to (i.e., destroying) the
* operation. A null callback function is used for a synchronous
* request; in that case return from this function won't occur until
* the operation is complete.
*/
int gb_operation_request_send(struct gb_operation *operation,
gb_operation_callback callback)
{
unsigned long timeout;
int ret;
if (operation->connection->state != GB_CONNECTION_STATE_ENABLED)
return -ENOTCONN;
/*
* First, get an extra reference on the operation.
* It'll be dropped when the operation completes.
*/
gb_operation_get(operation);
/* A null callback pointer means synchronous return */
if (callback)
operation->callback = callback;
else
operation->callback = gb_operation_sync_callback;
gb_pending_operation_insert(operation);
/*
* We impose a time limit for requests to complete. We need
* to set the timer before we send the request though, so we
* don't lose a race with the receipt of the resposne.
*/
timeout = msecs_to_jiffies(OPERATION_TIMEOUT_DEFAULT);
schedule_delayed_work(&operation->timeout_work, timeout);
/* All set, send the request */
gb_operation_result_set(operation, -EINPROGRESS);
ret = gb_message_send(operation->request);
if (ret || callback)
return ret;
/* Cancel the operation if interrupted */
ret = wait_for_completion_interruptible(&operation->completion);
if (ret < 0)
gb_operation_cancel(operation, -ECANCELED);
return gb_operation_result(operation);
}
/*
* Send a response for an incoming operation request.
*/
int gb_operation_response_send(struct gb_operation *operation)
{
gb_operation_destroy(operation);
return 0;
}
/*
* This function is called when a buffer send request has completed.
* The "header" is the message header--the beginning of what we
* asked to have sent.
*/
void
greybus_data_sent(struct greybus_host_device *hd, void *header, int status)
{
struct gb_message *message;
struct gb_operation *operation;
/* XXX Right now we assume we're an outgoing request */
message = gb_hd_message_find(hd, header);
/* Record that the message is no longer in flight */
message->cookie = NULL;
/* If there's no error, there's really nothing more to do */
if (!status)
return; /* Mark it complete? */
operation = message->operation;
if (gb_operation_result_set(operation, status))
queue_work(gb_operation_workqueue, &operation->work);
}
EXPORT_SYMBOL_GPL(greybus_data_sent);
/*
* We've received data on a connection, and it doesn't look like a
* response, so we assume it's a request.
*
* This is called in interrupt context, so just copy the incoming
* data into the request buffer and handle the rest via workqueue.
*/
static void gb_connection_recv_request(struct gb_connection *connection,
u16 operation_id, u8 type, void *data,
size_t size)
{
struct gb_operation *operation;
operation = gb_operation_create_incoming(connection, operation_id,
type, data, size);
if (!operation) {
gb_connection_err(connection, "can't create operation");
return; /* XXX Respond with pre-allocated ENOMEM */
}
/* XXX Right now this will just complete the operation */
if (gb_operation_result_set(operation, -ENOSYS))
queue_work(gb_operation_workqueue, &operation->work);
}
/*
* We've received data that appears to be an operation response
* message. Look up the operation, and record that we've received
* its response.
*
* This is called in interrupt context, so just copy the incoming
* data into the response buffer and handle the rest via workqueue.
*/
static void gb_connection_recv_response(struct gb_connection *connection,
u16 operation_id, void *data, size_t size)
{
struct gb_operation *operation;
struct gb_message *message;
int result;
operation = gb_pending_operation_find(connection, operation_id);
if (!operation) {
gb_connection_err(connection, "operation not found");
return;
}
cancel_delayed_work(&operation->timeout_work);
gb_pending_operation_remove(operation);
message = operation->response;
result = gb_operation_status_map(message->header->result);
if (!result && size != message->size) {
gb_connection_err(connection, "bad message size (%zu != %zu)",
size, message->size);
result = -EMSGSIZE;
}
/* We must ignore the payload if a bad status is returned */
if (result)
size = sizeof(*message->header);
memcpy(message->header, data, size);
/* The rest will be handled in work queue context */
if (gb_operation_result_set(operation, result))
queue_work(gb_operation_workqueue, &operation->work);
}
/*
* Handle data arriving on a connection. As soon as we return the
* supplied data buffer will be reused (so unless we do something
* with, it's effectively dropped).
*/
void gb_connection_recv(struct gb_connection *connection,
void *data, size_t size)
{
struct gb_operation_msg_hdr *header;
size_t msg_size;
u16 operation_id;
if (connection->state != GB_CONNECTION_STATE_ENABLED) {
gb_connection_err(connection, "dropping %zu received bytes",
size);
return;
}
if (size < sizeof(*header)) {
gb_connection_err(connection, "message too small");
return;
}
header = data;
msg_size = (size_t)le16_to_cpu(header->size);
if (msg_size > size) {
gb_connection_err(connection, "incomplete message");
return; /* XXX Should still complete operation */
}
operation_id = le16_to_cpu(header->operation_id);
if (header->type & GB_OPERATION_TYPE_RESPONSE)
gb_connection_recv_response(connection, operation_id,
data, msg_size);
else
gb_connection_recv_request(connection, operation_id,
header->type, data, msg_size);
}
/*
* Cancel an operation, and record the given error to indicate why.
*/
void gb_operation_cancel(struct gb_operation *operation, int errno)
{
if (gb_operation_result_set(operation, errno)) {
gb_message_cancel(operation->request);
gb_message_cancel(operation->response);
}
}
/**
* gb_operation_sync: implement a "simple" synchronous gb operation.
* @connection: the Greybus connection to send this to
* @type: the type of operation to send
* @request: pointer to a memory buffer to copy the request from
* @request_size: size of @request
* @response: pointer to a memory buffer to copy the response to
* @response_size: the size of @response.
*
* This function implements a simple synchronous Greybus operation. It sends
* the provided operation request and waits (sleeps) until the corresponding
* operation response message has been successfully received, or an error
* occurs. @request and @response are buffers to hold the request and response
* data respectively, and if they are not NULL, their size must be specified in
* @request_size and @response_size.
*
* If a response payload is to come back, and @response is not NULL,
* @response_size number of bytes will be copied into @response if the operation
* is successful.
*
* If there is an error, the response buffer is left alone.
*/
int gb_operation_sync(struct gb_connection *connection, int type,
void *request, int request_size,
void *response, int response_size)
{
struct gb_operation *operation;
int ret;
if ((response_size && !response) ||
(request_size && !request))
return -EINVAL;
operation = gb_operation_create(connection, type,
request_size, response_size);
if (!operation)
return -ENOMEM;
if (request_size)
memcpy(&operation->request->payload, request, request_size);
/* Synchronous operation--no callback */
ret = gb_operation_request_send(operation, NULL);
if (ret)
pr_err("version operation failed (%d)\n", ret);
else
if (response_size)
memcpy(response, operation->response->payload,
response_size);
gb_operation_destroy(operation);
return ret;
}
int gb_operation_init(void)
{
BUILD_BUG_ON(GB_OPERATION_MESSAGE_SIZE_MAX >
U16_MAX - sizeof(struct gb_operation_msg_hdr));
gb_operation_cache = kmem_cache_create("gb_operation_cache",
sizeof(struct gb_operation), 0, 0, NULL);
if (!gb_operation_cache)
return -ENOMEM;
gb_operation_workqueue = alloc_workqueue("greybus_operation", 0, 1);
if (!gb_operation_workqueue) {
kmem_cache_destroy(gb_operation_cache);
gb_operation_cache = NULL;
return -ENOMEM;
}
return 0;
}
void gb_operation_exit(void)
{
destroy_workqueue(gb_operation_workqueue);
gb_operation_workqueue = NULL;
kmem_cache_destroy(gb_operation_cache);
gb_operation_cache = NULL;
}
