spi: core: add spi_replace_transfers method
Add the spi_replace_transfers method that can get used
to replace some spi_transfers from a spi_message with other
transfers.
Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 894ed03..2ec8e66a 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2107,6 +2107,138 @@
/*-------------------------------------------------------------------------*/
+/* Core methods for spi_message alterations */
+
+static void __spi_replace_transfers_release(struct spi_master *master,
+ struct spi_message *msg,
+ void *res)
+{
+ struct spi_replaced_transfers *rxfer = res;
+ size_t i;
+
+ /* call extra callback if requested */
+ if (rxfer->release)
+ rxfer->release(master, msg, res);
+
+ /* insert replaced transfers back into the message */
+ list_splice(&rxfer->replaced_transfers, rxfer->replaced_after);
+
+ /* remove the formerly inserted entries */
+ for (i = 0; i < rxfer->inserted; i++)
+ list_del(&rxfer->inserted_transfers[i].transfer_list);
+}
+
+/**
+ * spi_replace_transfers - replace transfers with several transfers
+ * and register change with spi_message.resources
+ * @msg: the spi_message we work upon
+ * @xfer_first: the first spi_transfer we want to replace
+ * @remove: number of transfers to remove
+ * @insert: the number of transfers we want to insert instead
+ * @release: extra release code necessary in some circumstances
+ * @extradatasize: extra data to allocate (with alignment guarantees
+ * of struct @spi_transfer)
+ *
+ * Returns: pointer to @spi_replaced_transfers,
+ * PTR_ERR(...) in case of errors.
+ */
+struct spi_replaced_transfers *spi_replace_transfers(
+ struct spi_message *msg,
+ struct spi_transfer *xfer_first,
+ size_t remove,
+ size_t insert,
+ spi_replaced_release_t release,
+ size_t extradatasize,
+ gfp_t gfp)
+{
+ struct spi_replaced_transfers *rxfer;
+ struct spi_transfer *xfer;
+ size_t i;
+
+ /* allocate the structure using spi_res */
+ rxfer = spi_res_alloc(msg->spi, __spi_replace_transfers_release,
+ insert * sizeof(struct spi_transfer)
+ + sizeof(struct spi_replaced_transfers)
+ + extradatasize,
+ gfp);
+ if (!rxfer)
+ return ERR_PTR(-ENOMEM);
+
+ /* the release code to invoke before running the generic release */
+ rxfer->release = release;
+
+ /* assign extradata */
+ if (extradatasize)
+ rxfer->extradata =
+ &rxfer->inserted_transfers[insert];
+
+ /* init the replaced_transfers list */
+ INIT_LIST_HEAD(&rxfer->replaced_transfers);
+
+ /* assign the list_entry after which we should reinsert
+ * the @replaced_transfers - it may be spi_message.messages!
+ */
+ rxfer->replaced_after = xfer_first->transfer_list.prev;
+
+ /* remove the requested number of transfers */
+ for (i = 0; i < remove; i++) {
+ /* if the entry after replaced_after it is msg->transfers
+ * then we have been requested to remove more transfers
+ * than are in the list
+ */
+ if (rxfer->replaced_after->next == &msg->transfers) {
+ dev_err(&msg->spi->dev,
+ "requested to remove more spi_transfers than are available\n");
+ /* insert replaced transfers back into the message */
+ list_splice(&rxfer->replaced_transfers,
+ rxfer->replaced_after);
+
+ /* free the spi_replace_transfer structure */
+ spi_res_free(rxfer);
+
+ /* and return with an error */
+ return ERR_PTR(-EINVAL);
+ }
+
+ /* remove the entry after replaced_after from list of
+ * transfers and add it to list of replaced_transfers
+ */
+ list_move_tail(rxfer->replaced_after->next,
+ &rxfer->replaced_transfers);
+ }
+
+ /* create copy of the given xfer with identical settings
+ * based on the first transfer to get removed
+ */
+ for (i = 0; i < insert; i++) {
+ /* we need to run in reverse order */
+ xfer = &rxfer->inserted_transfers[insert - 1 - i];
+
+ /* copy all spi_transfer data */
+ memcpy(xfer, xfer_first, sizeof(*xfer));
+
+ /* add to list */
+ list_add(&xfer->transfer_list, rxfer->replaced_after);
+
+ /* clear cs_change and delay_usecs for all but the last */
+ if (i) {
+ xfer->cs_change = false;
+ xfer->delay_usecs = 0;
+ }
+ }
+
+ /* set up inserted */
+ rxfer->inserted = insert;
+
+ /* and register it with spi_res/spi_message */
+ spi_res_add(msg, rxfer);
+
+ return rxfer;
+}
+EXPORT_SYMBOL_GPL(spi_replace_transfers);
+
+/*-------------------------------------------------------------------------*/
+
/* Core methods for SPI master protocol drivers. Some of the
* other core methods are currently defined as inline functions.
*/