Re: [PATCH v2] treewide, serdev: change receive_buf() return type to size_t
From: Alex Elder <hidden>
Date: 2024-01-24 21:59:50
Also in:
chrome-platform, linux-arm-kernel, linux-bluetooth, linux-iio, linux-mediatek, linux-serial, linux-sound, lkml, platform-driver-x86
On 1/22/24 12:05 PM, Francesco Dolcini wrote:
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.
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.Agreed.
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.
I was going to suggest this, and suggest changing the "ret" in gnss_insert_raw() to return size_t. But to really do that right it would include some other changes as well. Leaving it as an int as Johan suggests preserves correct behavior. One minor point below, plus a couple comments affirming that an int return value is OK because it's always non-negative. Reviewed-by: Alex Elder <redacted>
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> Acked-by: Jonathan Cameron <redacted> #for-iio --- v1: - https://lore.kernel.org/all/20231214170146.641783-1-francesco@dolcini.it/ (local) v2: - rebased on 6.8-rc1 - add acked-by Jonathan - do not change gnss_insert_raw() - do not change the code style of the gnss code - commit message improvements, explain the reasons for doing only minimal changes on the GNSS part --- drivers/bluetooth/btmtkuart.c | 4 ++-- drivers/bluetooth/btnxpuart.c | 4 ++-- drivers/bluetooth/hci_serdev.c | 4 ++-- drivers/gnss/serial.c | 2 +- drivers/gnss/sirf.c | 2 +- drivers/greybus/gb-beagleplay.c | 6 +++--- drivers/iio/chemical/pms7003.c | 4 ++-- drivers/iio/chemical/scd30_serial.c | 4 ++-- drivers/iio/chemical/sps30_serial.c | 4 ++-- drivers/iio/imu/bno055/bno055_ser_core.c | 4 ++-- drivers/mfd/rave-sp.c | 4 ++-- drivers/net/ethernet/qualcomm/qca_uart.c | 2 +- drivers/nfc/pn533/uart.c | 4 ++-- drivers/nfc/s3fwrn5/uart.c | 4 ++-- drivers/platform/chrome/cros_ec_uart.c | 4 ++-- drivers/platform/surface/aggregator/core.c | 4 ++-- drivers/tty/serdev/serdev-ttyport.c | 10 ++++------ include/linux/serdev.h | 8 ++++---- sound/drivers/serial-generic.c | 4 ++-- 19 files changed, 40 insertions(+), 42 deletions(-)
. . .
quoted hunk ↗ jump to hunk
diff --git a/drivers/mfd/rave-sp.c b/drivers/mfd/rave-sp.c index 6ff84b2600c5..62a6613fb070 100644 --- a/drivers/mfd/rave-sp.c +++ b/drivers/mfd/rave-sp.c@@ -471,8 +471,8 @@ static void rave_sp_receive_frame(struct rave_sp *sp, rave_sp_receive_reply(sp, data, length); } -static ssize_t rave_sp_receive_buf(struct serdev_device *serdev, - const u8 *buf, size_t size) +static size_t rave_sp_receive_buf(struct serdev_device *serdev, + const u8 *buf, size_t size) { struct device *dev = &serdev->dev; struct rave_sp *sp = dev_get_drvdata(dev);
One return path in this function returns (src - buf), which is *almost* guaranteed to be positive. The one case it wouldn't be is if the assignment of end wraps around, and that's not checked. I think it's fine, but... That seems theoretically possible.
quoted hunk ↗ jump to hunk
diff --git a/drivers/net/ethernet/qualcomm/qca_uart.c b/drivers/net/ethernet/qualcomm/qca_uart.c index 223321897b96..20f50bde82ac 100644
. . .
quoted hunk ↗ jump to hunk
diff --git a/drivers/platform/surface/aggregator/core.c b/drivers/platform/surface/aggregator/core.c index 9591a28bc38a..ba550eaa06fc 100644 --- a/drivers/platform/surface/aggregator/core.c +++ b/drivers/platform/surface/aggregator/core.c@@ -227,8 +227,8 @@ EXPORT_SYMBOL_GPL(ssam_client_bind); /* -- Glue layer (serdev_device -> ssam_controller). ------------------------ */ -static ssize_t ssam_receive_buf(struct serdev_device *dev, const u8 *buf, - size_t n) +static size_t ssam_receive_buf(struct serdev_device *dev, const u8 *buf, + size_t n) { struct ssam_controller *ctrl; int ret;
Here you the return value will be positive despite ret being a signed int. So like the GNSS case, this is OK.
quoted hunk ↗ jump to hunk
diff --git a/drivers/tty/serdev/serdev-ttyport.c b/drivers/tty/serdev/serdev-ttyport.c index e94e090cf0a1..3d7ae7fa5018 100644
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quoted hunk ↗ jump to hunk
diff --git a/sound/drivers/serial-generic.c b/sound/drivers/serial-generic.c index d6e5aafd697c..36409a56c675 100644 --- a/sound/drivers/serial-generic.c +++ b/sound/drivers/serial-generic.c@@ -100,8 +100,8 @@ static void snd_serial_generic_write_wakeup(struct serdev_device *serdev) snd_serial_generic_tx_wakeup(drvdata); } -static ssize_t snd_serial_generic_receive_buf(struct serdev_device *serdev, - const u8 *buf, size_t count) +static size_t snd_serial_generic_receive_buf(struct serdev_device *serdev, + const u8 *buf, size_t count) { int ret; struct snd_serial_generic *drvdata = serdev_device_get_drvdata(serdev);
Same thing here.