Re: [PATCH v5 2/6] iio: backend: add support for data size set

David Lechner
2024-11-01T19:23:16Z

On 11/1/24 6:23 AM, Antoniu Miclaus wrote:
> Add backend support for setting the data size used.
> This setting can be adjusted within the IP cores interfacing devices.
>
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
> ---
> no changes in v5.
> drivers/iio/industrialio-backend.c | 21 +++++++++++++++++++++
> include/linux/iio/backend.h | 3 +++
> 2 files changed, 24 insertions(+)
>
> diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c
> index c792cd1e24e8..6f4e38417dfd 100644
> --- a/drivers/iio/industrialio-backend.c
> +++ b/drivers/iio/industrialio-backend.c
> @@ -660,6 +660,27 @@ int iio_backend_interface_type_get(struct iio_backend *back,
> }
> EXPORT_SYMBOL_NS_GPL(iio_backend_interface_type_get, IIO_BACKEND);
>
> +/**
> + * iio_backend_data_size_set - set the data width/size in the data bus.
> + * @back: Backend device
> + * @size: Size in bits
> + *
> + * Some frontend devices can dynamically control the word/data size on the
> + * interface/data bus. Hence, the backend device needs to be aware of it so
> + * data can be correctly transferred.
> + *
> + * Return:
> + * 0 on success, negative error number on failure.
> + */
> +size_t iio_backend_data_size_set(struct iio_backend *back, size_t size)

Should be returning int, not size_t.

Also, size_t for size parameter seems a bit much when this is taking bits.
I don't think anything is ever going to need 5 billion bits. :-p

> +{
> + if (!size)
> + return -EINVAL;
> +
> + return iio_backend_op_call(back, data_size_set, size);
> +}
> +EXPORT_SYMBOL_NS_GPL(iio_backend_data_size_set, IIO_BACKEND);
> +
> /**
> * iio_backend_extend_chan_spec - Extend an IIO channel
> * @back: Backend device
> diff --git a/include/linux/iio/backend.h b/include/linux/iio/backend.h
> index e5ea90f1c3e0..83ca4f0124db 100644
> --- a/include/linux/iio/backend.h
> +++ b/include/linux/iio/backend.h
> @@ -93,6 +93,7 @@ enum iio_backend_interface_type {
> * @ext_info_set: Extended info setter.
> * @ext_info_get: Extended info getter.
> * @interface_type_get: Interface type.
> + * @data_size_set: Data size.
> * @read_raw: Read a channel attribute from a backend device
> * @debugfs_print_chan_status: Print channel status into a buffer.
> * @debugfs_reg_access: Read or write register value of backend.
> @@ -130,6 +131,7 @@ struct iio_backend_ops {
> const struct iio_chan_spec *chan, char *buf);
> int (*interface_type_get)(struct iio_backend *back,
> enum iio_backend_interface_type *type);
> + int (*data_size_set)(struct iio_backend *back, ssize_t size);
> int (*read_raw)(struct iio_backend *back,
> struct iio_chan_spec const *chan, int *val, int *val2,
> long mask);
> @@ -180,6 +182,7 @@ ssize_t iio_backend_ext_info_get(struct iio_dev *indio_dev, uintptr_t private,
> const struct iio_chan_spec *chan, char *buf);
> int iio_backend_interface_type_get(struct iio_backend *back,
> enum iio_backend_interface_type *type);
> +size_t iio_backend_data_size_set(struct iio_backend *back, size_t size);

This will need to be changed as well.

> int iio_backend_read_raw(struct iio_backend *back,
> struct iio_chan_spec const *chan, int *val, int *val2,
> long mask);