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>

1 files changed, 3 insertions, 3 deletions

diff --git a/drivers/greybus/gb-beagleplay.c b/drivers/greybus/gb-beagleplay.c
index c3e90025064b..33f8fad70260 100644
--- a/drivers/greybus/gb-beagleplay.c
+++ b/drivers/greybus/gb-beagleplay.c
@@ -271,7 +271,7 @@ static void hdlc_rx_frame(struct gb_beagleplay *bg)
 	}
 }
 
-static ssize_t hdlc_rx(struct gb_beagleplay *bg, const u8 *data, size_t count)
+static size_t hdlc_rx(struct gb_beagleplay *bg, const u8 *data, size_t count)
 {
 	size_t i;
 	u8 c;
@@ -331,8 +331,8 @@ static void hdlc_deinit(struct gb_beagleplay *bg)
 	flush_work(&bg->tx_work);
 }
 
-static ssize_t gb_tty_receive(struct serdev_device *sd, const u8 *data,
-			      size_t count)
+static size_t gb_tty_receive(struct serdev_device *sd, const u8 *data,
+			     size_t count)
 {
 	struct gb_beagleplay *bg = serdev_device_get_drvdata(sd);