An asynchronous operation will want to know how big the response
message it receives is.  Rather than require the sender to record
that information, expose a new field "payload_size" available to
the protocol code for this purpose.

An operation message consists of a header and a payload.  The size
of the message can be derived from the size of the payload, so
record only the payload size and not the size of the whole message.
Reorder the fields in a message structure.

Update the description of the message header structure.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

This is in preparation for an upcoming patch, which makes the
payload pointer be NULL when a message has zero bytes of payload.

It ensures a null payload pointer never gets dereferenced.  To do
this we pass the response structure to gb_i2c_transfer_response()
rather than just its data, and if it's null, returning immediately.

Rearrange the logic in gb_i2c_transfer_operation() a bit.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

The connection->private pointer should refer to a protocol-specific
data structure.  Change two protocol drivers (USB and vibrator) so
they now set this.

In addition, because the setup routine may need access to the
data structure, the private pointer should be set early--as
early as possible.  Make the UART, i2c, and GPIO protocol drivers
set the private pointer earlier.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

The error message printed by gb_operation_sync() if the operation
fails is wrong.  Fix it.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

Define a new function used to initiate a synchronous operation.
It sends the operation request message and doesn't return until
the response has been received and/or the operation's result
has been set.

This gets rid of the convention that a null callback pointer
signifies a synchronous operation.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

There's no need to protect updating a connections operation id cycle
counter with the operations spinlock.   That spinlock protects
connection lists, which do not interact with the cycle counter.
All that we require is that it gets updated atomically, and we
can express that requirement in its type.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

A connection has two lists of operations, and an operation is always
on one or the other of them.  One of them contains the operations
that are currently "in flight".

We really don't expect to have very many in-flight operations on any
given connection (in fact, at the moment it's always exactly one).
So there's no significant performance benefit to keeping these in a
separate list.  An in-flight operation can also be distinguished by
its errno field holding -EINPROGRESS.

Get rid of the pending list, and search all operations rather than
the pending list when looking up a response message's operation.
Rename gb_pending_operation_find() accordingly.

There's no longer any need to remove operations from the pending
list, and the insertion function no longer has anything to do with a
pending list.  Just open code what was the insertion function (it
now has only to do with assigning the operation id).
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

Stop allowing 0x0000 to be used as an operation id.  That id will be
reserved for use by operations that will return no response message.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

Use a symbolic constant (rather than just "0") to represent an
explicitly invalid operation type.  The protocols have all reserved
that value for that purpose--this just makes it explicit in the core
code (since we now leverage its existence).  Fix the code so it uses
the new symbolic value.

Define it in "operation.h" for all to see.  Move the common
definition of the GB_OPERATION_TYPE_RESPONSE flag mask there
as well.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

The memcpy of request data into the request payload was
copying the data into the wrong location.  Fix that.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

The PWM config request defines two 32-bit values using u32. All
over-the-wire values have to be in little-endian format.  Fix this.
Signed-off-by: Alex Elder <elder@linaro.org>
Acked-by: Matt Porter <mporter@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

Define a helper function gb_operation_response_alloc() and use it
to allocate the response buffer for outgoing operations in
gb_operation_create_common(.

Use it also in  gb_operation_response_send() if the caller has not
allocated a response buffer.

Once a response buffer is allocated, fill in its result code and
send it.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

Define gb_operation_errno_map(), which maps an operation->errno
into the u8 value that represents it in the status field of an
operation response header.  It'll be used in an upcoming patch.

Make gb_operation_status_map() a private function.  It's not used
outside "operation.c" and I don't believe it ever should be.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

Un-comment gb_operation_request_handle(), which was recently
disabled to avoid distraction.

In gb_connection_recv_request(), activate handling incoming
requests by defining gb_operation_request_handle() as an
incoming operation's callback function.

Incoming operation requests have
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

Change gb_operation_response_send() so it takes an errno to assign
as an operation's result.  This emphasizes that setting the result
should be the last thing done to an incoming operation before
sending its response.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

A large number of request and response message types have no payload.
Such "simple" messages have a known, fixed maximum size, so we can
preallocate and use a pool (slab cache) of them.

Here are two benefits to doing this:
    - There can be (small) performance and memory utilization
      benefits to using a slab cache.
    - Error responses can be sent with no payload; the cache is
      likely to have a free entry to use for an error response even
      in a low memory situation.

The plan here is that an incoming request handler that has no
response payload to fill will not need to allocate a response
message.  If no message has been allocated when a response is to be
sent, one will be allocated from the cache by the core code.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

Define a maximum size that a host device can use for its private
area ahead of the payload space used by Greybus in a message buffer.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

Separate the allocation of a message structure from its basic
initialization.  This will allow very common fixed-size operation
response buffers to be allocated from a slab cache.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

When incoming data is going to be handled as a request, we create a
new operation whose request buffer will hold the received data.
There is no need to initialize the message header in such a request
buffer because it will be immediately overwritten.

Use operation type value of 0x00 in gb_operation_create_common()
to signal that we are creating an incoming operation, and therefore
do not need to initialize the request message header.  This allows
us to get rid of the Boolean "outgoing" parameter.

As a result, we can stop supplying the "type" parameter to both
gb_operation_create_incoming() and gb_connection_recv_request().

Update the header comments for gb_operation_message_alloc() and
gb_operation_create_common().
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

The operation type 0x00 is reserved as an explicitly invalid
operation type in all protocols.  Enforce this.

Add a check for callers who erroneously have the RESPONSE message
type flag set in the operation type passed in gb_operation_create().
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

Pass the operation result to gb_connection_recv_response() as a
parameter.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

We enforce a rule that a response message must completely fill the
buffer that's been allocated to hold it.  However, if an error
occurs, the payload is off limits, so we should allow a short
message to convey an error result.

Change gb_connection_recv_response() to require the right message
size only if there's no error.

One other thing:  The arriving data is only being copied into the
response buffer if the request was successful.  That means the
response message header is assumed to have been initialized.  That
isn't a valid assumption.  So change it so that if an error is
seen, the header portion of the message is copied into the
response buffer--but only the header.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

Currently incoming request data is copied into a request message
buffer in gb_connection_recv_request().  Move that--along with the
assignment of the message id--into gb_operation_create_incoming().
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

gb_connection_recv_request should be static, so mark it as such.
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

Currently we issue a warning in gb_operation_work() if an operation
has no callback function defined.  But we return without dropping
the reference to the operation as we should.

Stop warning if there's no callback, call it only if it's defined,
and always drop the operation reference before returning.

This means we're now treating a NULL callback pointer as a normal
condition.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

We will only send messages from process context.  Drop the gfp_mask
parameter from gb_message_send(), and just supply GFP_KERNEL to the
host driver's buffer_send method.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

Define a new operation status GB_OP_MALFUNCTION, which will be used
to represent that something unexpected happened while handling an
operation.  This is intended as an indication similar to a BUG()
call--whatever went wrong should *never* happen and because it's
unexpected we need to treat it as a fatal error.

Define another new operation status GB_OP_UNKNOWN_ERROR, which
will represent the case where an operation ended in error, but
the error was not recognized to be properly represented by one
of the other status values.

Renumber the operation status values, defining those that are
produced by core operations code ahead of those that are more
likely to come from operation handlers.  Represent the values in
hexadecimal to emphasize that they must be represented with 8 bits.
The Use 0xff for GB_OP_MALFUNCTION instead of GB_OP_TIMEOUT; the
latter is special, but a malfunction is in a class by itself.

Reorder the cases in gb_operation_status_map() to match their
numeric order.

Map GB_OP_UNKNOWN_ERROR to -EIO in gb_operation_status_map().  Map
GB_OP_MALFUNCTION to -EILSEQ in gb_operation_status_map(), since
that value is used to represent an implementation error.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

Reserve operation result code -EILSEQ to represent that the code
that implements an operation is broken.  This is used (initially)
for any attempt to set the result to -EBADR (which is reserved for
an operation in initial state), or for an attempt to set the result
of an operation that is *not* in initial state to -EINPROGRESS.

Note that we still use -EIO gb_operation_status_map() to represent a
gb_operation_result value that isn't recognized.

In gb_operation_result(), warn if operation->errno is -EBADR.  That
is another value that indicates the operation is not in a state
where it's valid to query an operation's result.

Update a bunch of comments above gb_operation_result_set() to
explain constraints on operation->errno.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

We represent the size of a message using a 16-bit field.  It's
possible for a host driver to advertise a maximum message size
that's bigger than that.  If that happens, reduce the host device's
maximum buffer size to the maximum we can represent the first time
a message is allocated.

This information is actually only used by the Greybus code, but
because we're modifying a value that's "owned" by the host driver,
issue a warning when this limit is being imposed

Ensure (at build time) that our own definition is sane as well.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

In gb_operation_create_common(), a zero response size is still
being used to determine whether to use GFP_KERNEL or GFP_ATOMIC
when allocating a message.  Use the value of the "outgoing"
parameter to decide this instead.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

Based on Fabien's original driver, this version is converted (mostly) to
the new greybus operation apis.  Lots of things still to do, not the
least being hooking up proper responses...
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

When a Greybus message is sent, the host driver supplies a cookie
for Greybus to use to identify the sent message in the event it
needs to be canceled.  The cookie will be non-null while the message
is in flight, and a null pointer otherwise.

There are two problems with this, which arise out of the fact that a
message can be canceled at any time--even concurrent with it getting
sent (such as when Greybus is getting shut down).

First, the host driver's buffer_send method can return an error
value, which is non-null but not a valid cookie.  So we need to
ensure such a bogus cookie is never used to cancel a message.

Second, we can't resolve that problem by assigning message->cookie
only after we've determined it's not an error.  The instant
buffer_send() returns, the message may well be in flight and *should*
be canceled at shutdown, so we need the cookie value to reflect
that.

In order to avoid these problems, protect access to a message's
cookie value with a mutex.  A spin lock can't be used because the
window that needs protecting covers code that can block.  We
reset the cookie value to NULL as soon as the host driver has
notified us it has been sent (or failed to).
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

It's possible for an in-flight buffer to be recorded as sent *after*
a thread has begin the process of canceling it.  In that case the
Greybus message cookie will be set to NULL, and that value can end
up getting passed to buffer_cancel().  Change buffer_cancel() so
it properly handles (ignores) a null cookie pointer.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

An operation result can be set both in and out of interrupt context.
For example, a response message could be arriving at the same time a
timeout of the operation is getting processed.  We therefore need to
ensure the result is accessed atomically.

Protect updates to the errno field using the operations spinlock.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

When an operation is created its receive buffer size is specified.
In all current cases, the size supplied for the receive buffer is
exactly the size that should be returned.  In other words, if
any fewer than that many bytes arrived in a response, it would be
an error.

So tighten the check on the number of bytes arriving for a response
message, ensuring that the number of bytes received is *exactly the
same* as the number of bytes available (rather than just less than).
We'll expand our interpretation of of -EMSGSIZE to mean "wrong
message size" rather than just "message too long."

If we someday encounter an actual case where we want to be able to
successfully receive something less than the full receive buffer we
can adjust the code to handle that (and give it a way to tell the
receiver how many bytes are present).
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

Change the message result values used in two cases.

First, use -EMSGSIZE rather than -E2BIG to represent a message
that is larger than the buffer intended to hold it.  That is
the proper code for this situation.

Second, use -ECANCELED rather than -EINTR for an operation that
has been canceled.  The definition of that error is literally
"Operation Canceled" so it seems like the right thing to do.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

This is more or less re-implementing this commit:
    96f95d4 greybus: update gbuf status for completion handlers
But this time we're doing this for an operation, not the gbuf.

Define an initial operation result value (-EBADR) to signify that no
valid result has been set.  Nobody should ever set that value after
the operation is initially created.  Since only the operation core
code sets the result, an attempt to set -EBADR would be a bug.

Define another known operation result value (-EINPROGRESS) for an
outgoing operation whose request has been sent but whose response
has not yet been successfully received.  This should the first
(non-initial) result value set, and it should happen exactly once.
Any other attempt to set this value once set would be a bug.

Finally, once the request message is in flight, the result value
will be set exactly once more, to indicate the final result of
the operation.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

If an operation already has an error result recorded, don't
overwrite it with a new error code.

In order to ensure a request completes exactly once, return a
Boolean indicating whether setting the result was successful.  If
two threads are racing to complete an operation (for example if a
slow-but-normal response message arrives at the same time timeout
processing commences) only the one that sets the final result
will finish its activity.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

Hide the setting and getting of the operation result (stored in
operation->errno) behind a pair of accessor functions.  Only the
operation core should be setting the result, but operations that
complete asynchronously will need access to the result so expose
the function that provides that.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

We always pass the same option to send_line_coding() for the line_coding
structure, which is already in the struct gb_tty variable, so just
remove the second parameter as it's not needed.

This logic came from the cdc-acm.c driver, where it's also not needed
anymore, I'll go fix up that later on when I get a chance.
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>