greybus: audio: apbridgea: Remove flexible array from struct audio_apbridgea_hdr

When a struct containing a flexible array is included in another struct,
and there is a member after the struct-with-flex-array, there is a
possibility of memory overlap. These cases must be audited [1]. See:

struct inner {
...
int flex[];
};

struct outer {
...
struct inner header;
int overlap;
...
};

This is the scenario for the "struct audio_apbridgea_hdr" structure
that is included in the following "struct audio_apbridgea_*_request"
structures:

struct audio_apbridgea_set_config_request
struct audio_apbridgea_register_cport_request
struct audio_apbridgea_unregister_cport_request
struct audio_apbridgea_set_tx_data_size_request
struct audio_apbridgea_prepare_tx_request
struct audio_apbridgea_start_tx_request
struct audio_apbridgea_stop_tx_request
struct audio_apbridgea_shutdown_tx_request
struct audio_apbridgea_set_rx_data_size_request
struct audio_apbridgea_prepare_rx_request
struct audio_apbridgea_start_rx_request
struct audio_apbridgea_stop_rx_request
struct audio_apbridgea_shutdown_rx_request

The pattern is like the one shown below:

struct audio_apbridgea_hdr {
...
__u8 data[];
} __packed;

struct audio_apbridgea_*_request {
struct audio_apbridgea_hdr hdr;
...
} __packed;

In this case, the trailing flexible array can be removed because it is
never used.

Link: https://github.com/KSPP/linux/issues/202 [1]
Signed-off-by: Erick Archer <erick.archer@gmx.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Acked-by: Mark Greer <mgreer@animalcreek.com>
Link: https://lore.kernel.org/r/20240217154758.7965-1-erick.archer@gmx.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

staging: Replace zero-length array with flexible-array member

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
int stuff;
struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Link: https://lore.kernel.org/r/20200220132908.GA30501@embeddedor
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

staging: greybus: remove license "boilerplate"

When the greybus drivers were converted to SPDX identifiers for the
license text, some license boilerplate was not removed. Clean this up
by removing this unneeded text now.

Cc: Johan Hovold <johan@kernel.org>
Cc: Vaibhav Agarwal <vaibhav.sr@gmail.com>
Cc: "Bryan O'Donoghue" <pure.logic@nexus-software.ie>
Cc: greybus-dev@lists.linaro.org
Cc: devel@driverdev.osuosl.org
Acked-by: Mark Greer <mgreer@animalcreekk.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Alex Elder <elder@kernel.org>
Link: https://lore.kernel.org/r/20190825055429.18547-3-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

staging: greybus: correct SPDX License Identifier

Replace SPDX License Identifier comments with C comments.
Reported by checkpatch.

Signed-off-by: Ioannis Valasakis <code@wizofe.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

staging: greybus: add SPDX identifiers to all greybus driver files

It's good to have SPDX identifiers in all files to make it easier to
audit the kernel tree for correct licenses.

Update the drivers/staging/greybus files files with the correct SPDX
license identifier based on the license text in the file itself. The
SPDX identifier is a legally binding shorthand, which can be used
instead of the full boiler plate text.

This work is based on a script and data from Thomas Gleixner, Philippe
Ombredanne, and Kate Stewart.

Cc: Vaibhav Hiremath <hvaibhav.linux@gmail.com>
Cc: "Bryan O'Donoghue" <pure.logic@nexus-software.ie>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Acked-by: Vaibhav Agarwal <vaibhav.sr@gmail.com>
Acked-by: David Lin <dtwlin@gmail.com>
Reviewed-by: Alex Elder <elder@linaro.org>
Acked-by: Johan Hovold <johan@kernel.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Mark Greer <mgreer@animalcreek.com>
Acked-by: Rui Miguel Silva <rmfrfs@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

greybus: audio: apbridgea: Remove GET_TX/RX_DELAY message types

The 'AUDIO_APBRIDGEA_TYPE_GET_TX_DELAY' and
'AUDIO_APBRIDGEA_TYPE_GET_RX_DELAY' message types have been
removed from the AP <-> APBrigdeA Audio Protocol so remove
them from the code. Do not coalesce the message type numbers
to prevent compatibility issues between the AP and APBridgeA.

Testing Done: Played music using a speaker module

Signed-off-by: Mark Greer <mgreer@animalcreek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

greybus: audio: Split start and stop APBridgeA requests

Provide finer-grained control of the audio streaming on APB1 by
splitting the transmit/receive start and stop requests into prepare,
start, stop, and shutdown.

CC: Vaibhav Agarwal <vaibhav.agarwal@linaro.org>
Signed-off-by: Mark Greer <mgreer@animalcreek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

greybus: audio: Register CPorts for specific directions

Currently, it is assumed that all audio data CPorts registered on
APB1 are used for transmitting audio data. That may not always be
true like when a microphone is connected but no speakers. Also,
the current special protocol lacks a way to tell APB1 whether the CPort
being registered is for transmitting, receiving, or both.

Fix by adding a 'direction' field to the register and unregister CPort
requests and define bits indicating which direction (or both) audio
data will go on that CPort.

Signed-off-by: Mark Greer <mgreer@animalcreek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

greybus: audio: Add direct audio streaming control for APBridgeA

The latest audio architecture does not stream audio data over the
USB link between the AP and APBridgeA. Instead, audio data is
streamed directly over the I2S link between the two.

To support the Greybus audio driver in setting up the I2S port and
controling packeting/depacketizing of audio data to/from Greybus
audio messages, define a set of commands and their parameters.
These commands and parameters will be placed into a request and sent
over the USB control channel to APBridgeA. A corresponding driver
on APBridgeA will receive and process the requests.

Signed-off-by: Mark Greer <mgreer@animalcreek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>