On 05/19/2012 01:14 PM, Jonathan Cameron wrote:
> By bypassing the standard macros for setting up the kfifo we can
> take advantage of the fixed record size implementation without
> having to have a type to pass in (from which the size of an element
> is normally established).
>
> In IIO we have variable 'scans' as our records in which any element
> can be present or not. They do not however vary when we are
> actually filling or reading from the buffer. Thus we have a fixed
> record size whenever we are actually running. As setup and tear
> down are not in the fast path we can take the overhead of reinitializing
> the kfifo every time.
>
> This is an RFC as
>
> a) I'm far from sure I got it right.
> b) There is probably a better way of doing it!
>
> Signed-off-by: Jonathan Cameron <jic23@xxxxxxxxxx>
> ---
> Note this is against current staging-next.
>
>
> drivers/iio/kfifo_buf.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iio/kfifo_buf.c b/drivers/iio/kfifo_buf.c
> index 6bf9d05..74b1cb8 100644
> --- a/drivers/iio/kfifo_buf.c
> +++ b/drivers/iio/kfifo_buf.c
> @@ -22,7 +22,8 @@ static inline int __iio_allocate_kfifo(struct iio_kfifo *buf,
> return -EINVAL;
>
> __iio_update_buffer(&buf->buffer, bytes_per_datum, length);
> - return kfifo_alloc(&buf->kf, bytes_per_datum*length, GFP_KERNEL);
> + return __kfifo_alloc((struct __kfifo *)&buf->kf, length,
> + bytes_per_datum, GFP_KERNEL);
> }
>
> static int iio_request_update_kfifo(struct iio_buffer *r)
> @@ -94,7 +95,7 @@ static int iio_store_to_kfifo(struct iio_buffer *r,
> {
> int ret;
> struct iio_kfifo *kf = iio_to_kfifo(r);
> - ret = kfifo_in(&kf->kf, data, r->bytes_per_datum);
> + ret = __kfifo_in((struct __kfifo *)&kf->kf, data, r->bytes_per_datum);
The last parameter has to be 1 now, since we want to store one record. And I
think we can still use kfifo_in(...), the macro magic take care of doing the
right thing.
> if (ret != r->bytes_per_datum)
> return -EBUSY;
> return 0;
> @@ -110,7 +111,7 @@ static int iio_read_first_n_kfifo(struct iio_buffer *r,
> return -EINVAL;
>
> n = rounddown(n, r->bytes_per_datum);
> - ret = kfifo_to_user(&kf->kf, buf, n, &copied);
Same here. n needs to be n / r->bytes_per_datum
> + ret = __kfifo_to_user((struct __kfifo *)&kf->kf, buf, n, &copied);
>
> return copied;
> }
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