Ring buffer API changes

[Mattemagikern]

Aims to address: #96860

[tmon-nordic]

For some reason this breaks my CDC ACM echo stress tester. I generally run a pseudorandom (with a known seed) sequence and expect the CDC ACM sample to echo it back. Prior to this PR, everything works fine. With this PR, after resetting the board, I keep getting mismatch always at byte 64512. I have 1024 byte long synchronization pattern before the pseudorandom sequence. 64512+1024=65536 seems to suggest that there is some sort of wrapping issue.

[Mattemagikern]

Hi!

Thanks for reviewing and testing!

Could you share the test with me?
I wrote this test but it didn't catch it. I tested with various size of both input & ring_buffer size.
The test should surpass the uint16_t overflow and would then hopefully trigger the behavior you found.

/*
USB_CDC_ACM_RINGBUF_SIZE = 1024
#define CDC_ACM_BUFFER_SIZE (CONFIG_CDC_ACM_BULK_EP_MPS)
CDC_ACM_BUFFER_SIZE == CDC_ACM_BULK_EP_MPS = 64 or 512
*/
static uint8_t big_buff[1024];
static uint8_t big_input[66*1024];
static uint8_t big_output[66*1024];
void fill_big_input(void)
{
	sys_rand_get(big_input, sizeof(big_input));
}

ZTEST(ringbuffer_api, test_stress_big)
{
	struct ring_buffer rb;
	ring_buffer_init(&rb, big_buff, sizeof(big_buff));
	fill_big_input();

	size_t read = 0;
	size_t written = 0;
	size_t to_write;
	size_t to_read;
	uint8_t *ref;
	while (read < sizeof(big_input)) {
		to_write = MIN(ring_buffer_write_ptr(&rb, &ref), sizeof(big_input) - written);
		zassert_true(to_write > 0, "there should be space in the buffer");
		memcpy(ref, &big_input[written], to_write);
		ring_buffer_commit(&rb, to_write);
		written += to_write;

		while (read < written) {
			to_read = ring_buffer_read_ptr(&rb, &ref);
			zassert_true(to_read > 0, "there should be space in the buffer");
			memcpy(&big_output[read], ref, to_read);
			ring_buffer_consume(&rb, to_read);
			read += to_read;
		}

	}
	LOG_HEXDUMP_DBG(&big_input[64*1024], 64, "big_input");
	LOG_HEXDUMP_DBG(&big_output[64*1024], 64, "big_output");
	zassert_mem_equal(big_input, big_output, sizeof(big_input), "read != written");
}

[sonarqubecloud]

Quality Gate passed

Issues
14 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.3% Duplication on New Code

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