Re: [PATCH RFC v6 3/5] iio: osf: add protocol decoding

[Andy Shevchenko <andriy.shevchenko@intel.com>]

On Mon, Jun 29, 2026 at 04:13:35AM +0900, Jinseob Kim wrote:
> Add helpers for decoding Open Sensor Fusion frame headers and supported
> message payloads.
> 
> The decoder validates the OSF0 wire magic, protocol major version,
> header length, payload bounds, reserved fields and CRC before exposing
> decoded frame contents to the rest of the driver.
> 
> Use explicit little-endian wire storage sizes and designated
> initializers for decoded output structures.

...

> +#include <linux/bits.h>
> +#include <linux/crc32.h>
> +#include <linux/errno.h>
> +#include <linux/limits.h>
> +#include <linux/types.h>
> +#include <linux/unaligned.h>

...

> +#define OSF_FRAME_MAGIC		0x3046534f /* "OSF0" little-endian */

#define OSF_FRAME_MAGIC		0x3046534f /* "OSF0", little-endian */

(mind a comma).

...

> +int osf_protocol_decode_sensor_sample(const struct osf_frame *frame,
> +				      struct osf_sensor_sample *sample)
> +{
> +	u16 channel_count;
> +	u16 sample_format;
> +	u16 sensor_type;
> +	size_t expected_len;
> +	const u8 *payload;
> +
> +	if (!frame || !sample || !frame->payload)
> +		return -EINVAL;
> +
> +	if (frame->message_type != OSF_MSG_SENSOR_SAMPLE)
> +		return -EPROTO;
> +
> +	if (frame->payload_len < OSF_SENSOR_SAMPLE_BASE_LEN)
> +		return -EMSGSIZE;
> +
> +	payload = frame->payload;
> +	sensor_type = get_unaligned_le16(payload);
> +	channel_count = get_unaligned_le16(payload + 4);
> +	sample_format = get_unaligned_le16(payload + 6);
> +
> +	if (!osf_sensor_type_valid(sensor_type))
> +		return -EPROTO;
> +
> +	if (!channel_count)
> +		return -EPROTO;
> +
> +	if (sample_format != OSF_SAMPLE_FORMAT_S32)
> +		return -EPROTO;
> +
> +	if (get_unaligned_le32(payload + 12))
> +		return -EPROTO;

> +	if (channel_count > (SIZE_MAX - OSF_SENSOR_SAMPLE_BASE_LEN) /
> +	    sizeof(__le32))
> +		return -EOVERFLOW;

Dead code because it's always 'false'? Hasn't compiler given a warning?
Always compile your code with `make W=1` using both compilers: clang and GCC.

> +	expected_len = OSF_SENSOR_SAMPLE_BASE_LEN + channel_count * sizeof(__le32);
> +	if (frame->payload_len != expected_len)
> +		return -EMSGSIZE;
> +
> +	*sample = (struct osf_sensor_sample) {
> +		.sensor_type = sensor_type,
> +		.sensor_index = get_unaligned_le16(payload + 2),
> +		.channel_count = channel_count,
> +		.sample_format = sample_format,
> +		.scale_nano = get_unaligned_le32(payload + 8),
> +		.samples = payload + OSF_SENSOR_SAMPLE_BASE_LEN,
> +	};
> +
> +	return 0;
> +}

...

> +	if (capability_count > (SIZE_MAX - OSF_CAP_REPORT_BASE_LEN) /
> +	    OSF_CAP_SENSOR_ENTRY_LEN)
> +		return -EOVERFLOW;

Ditto.

-- 
With Best Regards,
Andy Shevchenko