Re: [PATCH v7 3/5] counter: Add character device interface

On Thu, Jan 28, 2021 at 10:01:13AM +0100, Oleksij Rempel wrote:

Hello William,


On Fri, Dec 25, 2020 at 07:15:36PM -0500, William Breathitt Gray wrote:

quoted

This patch introduces a character device interface for the Counter
subsystem. Device data is exposed through standard character device read
operations. Device data is gathered when a Counter event is pushed by
the respective Counter device driver. Configuration is handled via ioctl
operations on the respective Counter character device node.

Cc: David Lechner <david@lechnology.com>
Cc: Gwendal Grignou <redacted>
Cc: Dan Carpenter <redacted>
Signed-off-by: William Breathitt Gray <redacted>
---

...

quoted

+struct counter_event {
+	__aligned_u64 timestamp;
+	__aligned_u64 value;
+	struct counter_watch watch;
+	__u8 errno;

This variable clashed in user space, as soon as you include errno.h,
with the libc's "magic" definition of errno. What about "err" instead.
I'm not sure it an __u8 is the proper type, IIRC usually it's an int.

Regards,
Oleksij
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Sure, I can rename this to avoid a possible clash with libc's errno.
Maybe "status" would be more apt to indicate that this is an exit status
for the event -- the code returned may simply be a warning and not
necessarily a critical error.

Regarding the datatype for this value, I've opened up the discussion in
my reply to David Lechner [1], so perhaps we can continue it there.

[1] https://lkml.org/lkml/2021/1/30/5

William Breathitt Gray