Re: [PATCH v1] treewide, serdev: change receive_buf() return type to size_t

On Fri, Dec 15, 2023 at 02:51:09PM +0100, Johan Hovold wrote:

On Thu, Dec 14, 2023 at 06:01:46PM +0100, Francesco Dolcini wrote:

quoted

From: Francesco Dolcini <redacted>

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.

Suggested-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/all/087be419-ec6b-47ad-851a-5e1e3ea5cfcc@kernel.org/ (local)
Signed-off-by: Francesco Dolcini <redacted>
---
hello,
patch is based on current linux next.

It has an obvious problem, it touches files from multiple subsystem in a single
patch that is complicated to review and eventually merge, just splitting this
would however not work, it will break bisectability and the build.

I am looking for advise on the best way to move forward.

I see the following options:
 - keep it as it is
 - break it down with a patch with each subsystem, and squash before applying
   from a single (tty?) subsystem
 - go for a multi stage approach, defining a new callback, move to it and in
   the end remove the original one, likewise it was done for i2c lately

---
 drivers/bluetooth/btmtkuart.c              |  4 ++--
 drivers/bluetooth/btnxpuart.c              |  4 ++--

quoted

diff --git a/drivers/bluetooth/btmtkuart.c b/drivers/bluetooth/btmtkuart.c
index 3c84fcbda01a..e6bc4a73c9fc 100644
--- a/drivers/bluetooth/btmtkuart.c
+++ b/drivers/bluetooth/btmtkuart.c

@@ -383,8 +383,8 @@ static void btmtkuart_recv(struct hci_dev *hdev, const u8 *data, size_t count)
 	}
 }
 
-static ssize_t btmtkuart_receive_buf(struct serdev_device *serdev,
-				     const u8 *data, size_t count)
+static size_t btmtkuart_receive_buf(struct serdev_device *serdev,
+				    const u8 *data, size_t count)
 {
 	struct btmtkuart_dev *bdev = serdev_device_get_drvdata(serdev);
 

diff --git a/drivers/bluetooth/btnxpuart.c b/drivers/bluetooth/btnxpuart.c
index 1d592ac413d1..056bef5b2919 100644
--- a/drivers/bluetooth/btnxpuart.c
+++ b/drivers/bluetooth/btnxpuart.c

@@ -1264,8 +1264,8 @@ static const struct h4_recv_pkt nxp_recv_pkts[] = {
 	{ NXP_RECV_FW_REQ_V3,   .recv = nxp_recv_fw_req_v3 },
 };
 
-static ssize_t btnxpuart_receive_buf(struct serdev_device *serdev,
-				     const u8 *data, size_t count)
+static size_t btnxpuart_receive_buf(struct serdev_device *serdev,
+				    const u8 *data, size_t count)
 {
 	struct btnxpuart_dev *nxpdev = serdev_device_get_drvdata(serdev);

A quick check of just the first two functions here shows that they can
return negative values.

This is already fixed. Patches are in next.

There were 3 buggy user of this API.
 - 1 patch was merged a few days ago in mainline
 - 2 patches are in next, the maintainer decided to wait for the next merge window

commit 687d2de93b11 ("Bluetooth: btmtkuart: fix recv_buf() return value")
commit 7954bbcdd7ea ("Bluetooth: btnxpuart: fix recv_buf() return value")
commit c8820c92caf0 ("platform/surface: aggregator: fix recv_buf() return value")

quoted

diff --git a/drivers/tty/serdev/serdev-ttyport.c b/drivers/tty/serdev/serdev-ttyport.c
index e94e090cf0a1..3d7ae7fa5018 100644
--- a/drivers/tty/serdev/serdev-ttyport.c
+++ b/drivers/tty/serdev/serdev-ttyport.c

@@ -27,19 +27,17 @@ static size_t ttyport_receive_buf(struct tty_port *port, const u8 *cp,
 {
 	struct serdev_controller *ctrl = port->client_data;
 	struct serport *serport = serdev_controller_get_drvdata(ctrl);
-	int ret;
+	size_t ret;
 
 	if (!test_bit(SERPORT_ACTIVE, &serport->flags))
 		return 0;
 
 	ret = serdev_controller_receive_buf(ctrl, cp, count);
 
-	dev_WARN_ONCE(&ctrl->dev, ret < 0 || ret > count,
-				"receive_buf returns %d (count = %zu)\n",
+	dev_WARN_ONCE(&ctrl->dev, ret > count,
+				"receive_buf returns %zu (count = %zu)\n",
 				ret, count);
-	if (ret < 0)
-		return 0;
-	else if (ret > count)
+	if (ret > count)
 		return count;
 
 	return ret;

So please do not apply this patch until the various implementations have
been fixed.

Johan