On Wednesday, 4 December 2024, 00:55:32 CET, Javier Carrasco wrote:
> The channel index is off by one unit if AS73211_SCAN_MASK_ALL is not
> set (optimized path for color channel readings), and it must be shifted
> instead of leaving an empty channel for the temperature when it is off.
>
> Once the channel index is fixed, the uninitialized channel must be set
> to zero to avoid pushing uninitialized data.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 403e5586b52e ("iio: light: as73211: New driver")
> Signed-off-by: Javier Carrasco <javier.carrasco.cruz@xxxxxxxxx>
> ---
> drivers/iio/light/as73211.c | 17 +++++++++++++----
> 1 file changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/iio/light/as73211.c b/drivers/iio/light/as73211.c
> index be0068081ebb..2d45dfeda406 100644
> --- a/drivers/iio/light/as73211.c
> +++ b/drivers/iio/light/as73211.c
> @@ -672,9 +672,12 @@ static irqreturn_t as73211_trigger_handler(int irq __always_unused, void *p)
>
> /* AS73211 starts reading at address 2 */
> ret = i2c_master_recv(data->client,
> - (char *)&scan.chan[1], 3 * sizeof(scan.chan[1]));
> + (char *)&scan.chan[0], 3 * sizeof(scan.chan[0]));
> if (ret < 0)
> goto done;
> +
> + /* Avoid pushing uninitialized data */
> + scan.chan[3] = 0;
> }
>
> if (data_result) {
> @@ -682,9 +685,15 @@ static irqreturn_t as73211_trigger_handler(int irq __always_unused, void *p)
> * Saturate all channels (in case of overflows). Temperature channel
> * is not affected by overflows.
> */
> - scan.chan[1] = cpu_to_le16(U16_MAX);
> - scan.chan[2] = cpu_to_le16(U16_MAX);
> - scan.chan[3] = cpu_to_le16(U16_MAX);
> + if (*indio_dev->active_scan_mask == AS73211_SCAN_MASK_ALL) {
> + scan.chan[1] = cpu_to_le16(U16_MAX);
> + scan.chan[2] = cpu_to_le16(U16_MAX);
> + scan.chan[3] = cpu_to_le16(U16_MAX);
> + } else {
> + scan.chan[0] = cpu_to_le16(U16_MAX);
> + scan.chan[1] = cpu_to_le16(U16_MAX);
> + scan.chan[2] = cpu_to_le16(U16_MAX);
> + }
> }
>
> iio_push_to_buffers_with_timestamp(indio_dev, &scan, iio_get_time_ns(indio_dev));
>
>
With this change, having only X, Y and Z in the scan_mask (without the
temperature channel) works fine.
But it looks that there is still another problem if a single color channel
(e.g. X) is omitted from the scan mask (which probably wouldn't make much
sense in practice). If I am right, the layout of scan.chan[] is also wrong for
that case, so e.g. if omitting X, the application will get the X values where
it expects the temperature value (which isn't read from the hardware at all).
Does it make sense to write a follow-up patch for this? I fear that taking all
possible combinations into account could make the driver more complicated than
necessary. Or is there a good example how to handle such combinations?
Tested-by: Christian Eggers <ceggers@xxxxxxx>
