treewide, serdev: change receive_buf() return type to size_t

receive_buf() is called from ttyport_receive_buf() that expects values
">= 0" from serdev_controller_receive_buf(), change its return type from
ssize_t to size_t.

The need for this clean-up was noticed while fixing a warning, see
commit 94d053942544 ("Bluetooth: btnxpuart: fix recv_buf() return value").
Changing the callback prototype to return an unsigned seems the best way
to document the API and ensure that is properly used.

GNSS drivers implementation of serdev receive_buf() callback return
directly the return value of gnss_insert_raw(). gnss_insert_raw()
returns a signed int, however this is not an issue since the value
returned is always positive, because of the kfifo_in() implementation.
gnss_insert_raw() could be changed to return also an unsigned, however
this is not implemented here as request by the GNSS maintainer Johan
Hovold.

Suggested-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/all/087be419-ec6b-47ad-851a-5e1e3ea5cfcc@kernel.org/
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> #for-iio
Reviewed-by: Johan Hovold <johan@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Alex Elder <elder@linaro.org>
Acked-by: Maximilian Luz <luzmaximilian@gmail.com> # for platform/surface
Acked-by: Lee Jones <lee@kernel.org>
Acked-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20240122180551.34429-1-francesco@dolcini.it
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

greybus: gb-beagleplay: Remove use of pad bytes

Make gb-beagleplay greybus spec compliant by moving cport information to
transport layer instead of using `header->pad` bytes.

Greybus HDLC frame now has the following payload:
1. le16 cport
2. gb_operation_msg_hdr msg_header
3. u8 *msg_payload

Fixes: ec558bbfea67 ("greybus: Add BeaglePlay Linux Driver")
Signed-off-by: Ayush Singh <ayushdevel1325@gmail.com>
Link: https://lore.kernel.org/r/20231217121133.74703-2-ayushdevel1325@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tty: serdev: convert to u8 and size_t

Switch character types to u8 and sizes to size_t. To conform to
characters/sizes in the rest of the tty layer.

This patch converts struct serdev_device_ops hooks and its
instantiations.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Cc: Rob Herring <robh@kernel.org>
Acked-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20231206073712.17776-24-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Revert "greybus: gb-beagleplay: Ensure le for values in transport"

This reverts commit 52eb67861ebeb2110318bd9fe33d85ddcf92aac7.

Turns out to not be correct, a new version will be generated later.

Link: https://lore.kernel.org/r/20231204131008.384583-1-ayushdevel1325@gmail.com
Cc: Ayush Singh <ayushdevel1325@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

greybus: gb-beagleplay: Ensure le for values in transport

Ensure that the following values are little-endian:
- header->pad (which is used for cport_id)
- header->size

Fixes: ec558bbfea67 ("greybus: Add BeaglePlay Linux Driver")
Reported-by: kernel test robot <yujie.liu@intel.com>
Closes: https://lore.kernel.org/r/202311072329.Xogj7hGW-lkp@intel.com/
Signed-off-by: Ayush Singh <ayushdevel1325@gmail.com>
Link: https://lore.kernel.org/r/20231203075312.255233-1-ayushdevel1325@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

greybus: Add BeaglePlay Linux Driver

Add the Greybus host driver for BeaglePlay board by BeagleBoard.org.

The current greybus setup involves running SVC in a user-space
application (GBridge) and using netlink to communicate with kernel
space. GBridge itself uses wpanusb kernel driver, so the greybus messages
travel from kernel space (gb_netlink) to user-space (GBridge) and then
back to kernel space (wpanusb) before reaching CC1352.

This driver directly communicates with CC1352 (running SVC Zephyr
application). Thus, it simplifies the complete greybus setup eliminating
user-space GBridge.

This driver is responsible for the following:
- Start SVC (CC1352) on driver load.
- Send/Receive Greybus messages to/from CC1352 using HDLC over UART.
- Print Logs from CC1352.
- Stop SVC (CC1352) on driver load.

Signed-off-by: Ayush Singh <ayushdevel1325@gmail.com>
Link: https://lore.kernel.org/r/20231017101116.178041-3-ayushdevel1325@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>