-/**
- * __lib_ring_buffer_copy_to_user - read data from ring_buffer to userspace
- * @bufb : buffer backend
- * @offset : offset within the buffer
- * @dest : destination userspace address
- * @len : length to copy to destination
- *
- * Should be protected by get_subbuf/put_subbuf.
- * access_ok() must have been performed on dest addresses prior to call this
- * function.
- * Returns -EFAULT on error, 0 if ok.
- */
-int __lib_ring_buffer_copy_to_user(struct lib_ring_buffer_backend *bufb,
- size_t offset, void __user *dest, size_t len)
-{
- struct channel_backend *chanb = &bufb->chan->backend;
- const struct lib_ring_buffer_config *config = chanb->config;
- size_t index;
- ssize_t pagecpy, orig_len;
- struct lib_ring_buffer_backend_pages *rpages;
- unsigned long sb_bindex, id;
-
- orig_len = len;
- offset &= chanb->buf_size - 1;
- index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT;
- if (unlikely(!len))
- return 0;
- for (;;) {
- pagecpy = min_t(size_t, len, PAGE_SIZE - (offset & ~PAGE_MASK));
- id = bufb->buf_rsb.id;
- sb_bindex = subbuffer_id_get_index(config, id);
- rpages = bufb->array[sb_bindex];
- CHAN_WARN_ON(chanb, config->mode == RING_BUFFER_OVERWRITE
- && subbuffer_id_is_noref(config, id));
- if (__copy_to_user(dest,
- rpages->p[index].virt + (offset & ~PAGE_MASK),
- pagecpy))
- return -EFAULT;
- len -= pagecpy;
- if (likely(!len))
- break;
- dest += pagecpy;
- offset += pagecpy;
- index = (offset & (chanb->subbuf_size - 1)) >> PAGE_SHIFT;
- /*
- * Underlying layer should never ask for reads across
- * subbuffers.
- */
- CHAN_WARN_ON(chanb, offset >= chanb->buf_size);
- }
- return 0;
-}
-EXPORT_SYMBOL_GPL(__lib_ring_buffer_copy_to_user);
-