staging:iio: add a callback buffer for in kernel push interface

This callback buffer is meant to be opaque to users, but basically
adds a very simple pass through buffer to which data may be
pushed when it is inserted into the buffer list.

Signed-off-by: Jonathan Cameron <jic23@kernel.org>

3 files changed, 120 insertions, 0 deletions

diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
index fc937aca71fb..65ae734c607d 100644
--- a/drivers/iio/Kconfig
+++ b/drivers/iio/Kconfig
@@ -20,6 +20,12 @@ config IIO_BUFFER
 
 if IIO_BUFFER
 
+config IIO_BUFFER_CB
+boolean "IIO callback buffer used for push in-kernel interfaces"
+        help
+          Should be selected by any drivers that do-inkernel push
+          usage.  That is, those where the data is pushed to the consumer.
+
 config IIO_KFIFO_BUF
         select IIO_TRIGGER
         tristate "Industrial I/O buffering based on kfifo"
diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
index 761f2b65ac52..31d76a07ec65 100644
--- a/drivers/iio/Makefile
+++ b/drivers/iio/Makefile
@@ -6,6 +6,7 @@ obj-$(CONFIG_IIO) += industrialio.o
 industrialio-y := industrialio-core.o industrialio-event.o inkern.o
 industrialio-$(CONFIG_IIO_BUFFER) += industrialio-buffer.o
 industrialio-$(CONFIG_IIO_TRIGGER) += industrialio-trigger.o
+industrialio-$(CONFIG_IIO_BUFFER_CB) += buffer_cb.o
 
 obj-$(CONFIG_IIO_TRIGGERED_BUFFER) += industrialio-triggered-buffer.o
 obj-$(CONFIG_IIO_KFIFO_BUF) += kfifo_buf.o
diff --git a/drivers/iio/buffer_cb.c b/drivers/iio/buffer_cb.c
new file mode 100644
index 000000000000..4d40e24f3721
--- /dev/null
+++ b/drivers/iio/buffer_cb.c
@@ -0,0 +1,113 @@
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/iio/buffer.h>
+#include <linux/iio/consumer.h>
+
+struct iio_cb_buffer {
+        struct iio_buffer buffer;
+        int (*cb)(u8 *data, void *private);
+        void *private;
+        struct iio_channel *channels;
+};
+
+static int iio_buffer_cb_store_to(struct iio_buffer *buffer, u8 *data)
+{
+        struct iio_cb_buffer *cb_buff = container_of(buffer,
+                                                     struct iio_cb_buffer,
+                                                     buffer);
+
+        return cb_buff->cb(data, cb_buff->private);
+}
+
+static struct iio_buffer_access_funcs iio_cb_access = {
+        .store_to = &iio_buffer_cb_store_to,
+};
+
+struct iio_cb_buffer *iio_channel_get_all_cb(const char *name,
+                                             int (*cb)(u8 *data,
+                                                       void *private),
+                                             void *private)
+{
+        int ret;
+        struct iio_cb_buffer *cb_buff;
+        struct iio_dev *indio_dev;
+        struct iio_channel *chan;
+
+        cb_buff = kzalloc(sizeof(*cb_buff), GFP_KERNEL);
+        if (cb_buff == NULL) {
+                ret = -ENOMEM;
+                goto error_ret;
+        }
+
+        cb_buff->private = private;
+        cb_buff->cb = cb;
+        cb_buff->buffer.access = &iio_cb_access;
+        INIT_LIST_HEAD(&cb_buff->buffer.demux_list);
+
+        cb_buff->channels = iio_channel_get_all(name);
+        if (IS_ERR(cb_buff->channels)) {
+                ret = PTR_ERR(cb_buff->channels);
+                goto error_free_cb_buff;
+        }
+
+        indio_dev = cb_buff->channels[0].indio_dev;
+        cb_buff->buffer.scan_mask
+                = kcalloc(BITS_TO_LONGS(indio_dev->masklength), sizeof(long),
+                          GFP_KERNEL);
+        if (cb_buff->buffer.scan_mask == NULL) {
+                ret = -ENOMEM;
+                goto error_release_channels;
+        }
+        chan = &cb_buff->channels[0];
+        while (chan->indio_dev) {
+                if (chan->indio_dev != indio_dev) {
+                        ret = -EINVAL;
+                        goto error_release_channels;
+                }
+                set_bit(chan->channel->scan_index,
+                        cb_buff->buffer.scan_mask);
+                chan++;
+        }
+
+        return cb_buff;
+
+error_release_channels:
+        iio_channel_release_all(cb_buff->channels);
+error_free_cb_buff:
+        kfree(cb_buff);
+error_ret:
+        return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(iio_channel_get_all_cb);
+
+int iio_channel_start_all_cb(struct iio_cb_buffer *cb_buff)
+{
+        return iio_update_buffers(cb_buff->channels[0].indio_dev,
+                                  &cb_buff->buffer,
+                                  NULL);
+}
+EXPORT_SYMBOL_GPL(iio_channel_start_all_cb);
+
+void iio_channel_stop_all_cb(struct iio_cb_buffer *cb_buff)
+{
+        iio_update_buffers(cb_buff->channels[0].indio_dev,
+                           NULL,
+                           &cb_buff->buffer);
+}
+EXPORT_SYMBOL_GPL(iio_channel_stop_all_cb);
+
+void iio_channel_release_all_cb(struct iio_cb_buffer *cb_buff)
+{
+        iio_channel_release_all(cb_buff->channels);
+        kfree(cb_buff);
+}
+EXPORT_SYMBOL_GPL(iio_channel_release_all_cb);
+
+struct iio_channel
+*iio_channel_cb_get_channels(const struct iio_cb_buffer *cb_buffer)
+{
+        return cb_buffer->channels;
+}
+EXPORT_SYMBOL_GPL(iio_channel_cb_get_channels);