On Wed, 17 Aug 2022 12:56:43 +0200
Artur Rojek <contact@xxxxxxxxxxxxxx> wrote:
> Don't try to access buffer data of a channel by its scan index. Instead,
> use the newly introduced `iio_find_channel_offset_in_buffer` to get the
> correct data offset.
>
> The scan index of a channel does not represent its position in a buffer,
> as the buffer will contain data for enabled channels only, affecting
> data offsets and alignment.
>
> Fixes: 2c2b364fddd5 ("Input: joystick - add ADC attached joystick driver.")
> Reported-by: Chris Morgan <macromorgan@xxxxxxxxxxx>
> Tested-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
> Signed-off-by: Artur Rojek <contact@xxxxxxxxxxxxxx>
> ---
> drivers/input/joystick/adc-joystick.c | 26 +++++++++++++++++---------
> 1 file changed, 17 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/input/joystick/adc-joystick.c b/drivers/input/joystick/adc-joystick.c
> index c0deff5d4282..aed853ebe1d1 100644
> --- a/drivers/input/joystick/adc-joystick.c
> +++ b/drivers/input/joystick/adc-joystick.c
> @@ -6,6 +6,7 @@
> #include <linux/ctype.h>
> #include <linux/input.h>
> #include <linux/iio/iio.h>
> +#include <linux/iio/buffer.h>
> #include <linux/iio/consumer.h>
> #include <linux/module.h>
> #include <linux/platform_device.h>
> @@ -46,36 +47,43 @@ static void adc_joystick_poll(struct input_dev *input)
> static int adc_joystick_handle(const void *data, void *private)
> {
> struct adc_joystick *joy = private;
> + struct iio_buffer *buffer;
> enum iio_endian endianness;
> - int bytes, msb, val, idx, i;
> - const u16 *data_u16;
> + int bytes, msb, val, off;
> + const u8 *chan_data;
> + unsigned int i;
> bool sign;
>
> bytes = joy->chans[0].channel->scan_type.storagebits >> 3;
>
> for (i = 0; i < joy->num_chans; ++i) {
> - idx = joy->chans[i].channel->scan_index;
> endianness = joy->chans[i].channel->scan_type.endianness;
> msb = joy->chans[i].channel->scan_type.realbits - 1;
> sign = tolower(joy->chans[i].channel->scan_type.sign) == 's';
> + buffer = iio_channel_cb_get_iio_buffer(joy->buffer);
> + off = iio_find_channel_offset_in_buffer(joy->chans[i].indio_dev,
> + joy->chans[i].channel,
> + buffer);
With this call replaced with one that instead uses
off = iio_find_channel_offset_in_buffer(joy->chans, i);
which I'm fairly sure is enough via the info in chans[x]->channel to establish this offset.
All is good, though you should probably cache it as doing that maths every
time seems excessive.
> + if (off < 0)
> + return off;
> +
> + chan_data = (const u8 *)data + off;
>
> switch (bytes) {
> case 1:
> - val = ((const u8 *)data)[idx];
> + val = *chan_data;
> break;
> case 2:
> - data_u16 = (const u16 *)data + idx;
> -
> /*
> * Data is aligned to the sample size by IIO core.
> * Call `get_unaligned_xe16` to hide type casting.
> */
> if (endianness == IIO_BE)
> - val = get_unaligned_be16(data_u16);
> + val = get_unaligned_be16(chan_data);
I obviously missed this previously but these are aligned so we don't need the
unaligned form.
> else if (endianness == IIO_LE)
> - val = get_unaligned_le16(data_u16);
> + val = get_unaligned_le16(chan_data);
> else /* IIO_CPU */
> - val = *data_u16;
> + val = *(const u16 *)chan_data;
> break;
> default:
> return -EINVAL;
