On Tue, Oct 13, 2015 at 7:05 PM, Lars-Peter Clausen <lars@xxxxxxxxxx> wrote:
> For buffers which have a fixed wake-up watermark the watermark attribute
> should be read-only. Add a new FIXED_WATERMARK flag to the
> struct iio_buffer_access_funcs, which can be set by a buffer
> implementation.
>
> Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
> ---
> drivers/iio/industrialio-buffer.c | 5 +++++
> include/linux/iio/buffer.h | 8 ++++++++
> 2 files changed, 13 insertions(+)
>
> diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> index 5f2c8c8..98a6447 100644
> --- a/drivers/iio/industrialio-buffer.c
> +++ b/drivers/iio/industrialio-buffer.c
> @@ -998,6 +998,8 @@ static DEVICE_ATTR(enable, S_IRUGO | S_IWUSR,
> iio_buffer_show_enable, iio_buffer_store_enable);
> static DEVICE_ATTR(watermark, S_IRUGO | S_IWUSR,
> iio_buffer_show_watermark, iio_buffer_store_watermark);
> +static struct device_attribute dev_attr_watermark_ro = __ATTR(watermark,
> + S_IRUGO, iio_buffer_show_watermark, NULL);
I think we can use DEVICE_ATTR_RO here.
>
> static struct attribute *iio_buffer_attrs[] = {
> &dev_attr_length.attr,
> @@ -1040,6 +1042,9 @@ int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev)
> if (!buffer->access->set_length)
> attr[0] = &dev_attr_length_ro.attr;
>
> + if (buffer->access->flags & INDIO_BUFFER_FLAG_FIXED_WATERMARK)
> + attr[2] = &dev_attr_watermark_ro.attr;
> +
Ok, this works :). Let's hope iio_buffer_attrs array new elements
will be always added at the end.
> if (buffer->attrs)
> memcpy(&attr[ARRAY_SIZE(iio_buffer_attrs)], buffer->attrs,
> sizeof(struct attribute *) * attrcount);
> diff --git a/include/linux/iio/buffer.h b/include/linux/iio/buffer.h
> index 1600c55..4d99a53 100644
> --- a/include/linux/iio/buffer.h
> +++ b/include/linux/iio/buffer.h
> @@ -18,6 +18,12 @@
> struct iio_buffer;
>
> /**
> + * INDIO_BUFFER_FLAG_FIXED_WATERMARK - Watermark level of the buffer can not be
> + * configured. It has a fixed value which will be buffer specific.
> + */
> +#define INDIO_BUFFER_FLAG_FIXED_WATERMARK BIT(0)
> +
> +/**
> * struct iio_buffer_access_funcs - access functions for buffers.
> * @store_to: actually store stuff to the buffer
> * @read_first_n: try to get a specified number of bytes (must exist)
> @@ -30,6 +36,7 @@ struct iio_buffer;
> * @release: called when the last reference to the buffer is dropped,
> * should free all resources allocated by the buffer.
> * @modes: Supported operating modes by this buffer type
> + * @flags: A bitmask combination of INDIO_BUFFER_FLAG_*
> *
> * The purpose of this structure is to make the buffer element
> * modular as event for a given driver, different usecases may require
> @@ -54,6 +61,7 @@ struct iio_buffer_access_funcs {
> void (*release)(struct iio_buffer *buffer);
>
> unsigned int modes;
> + unsigned int flags;
> };
>
> /**
> --
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