Re: [PATCH RFC v3 2/9] spi: add basic support for SPI offloading

On Tue, 30 Jul 2024 14:35:09 -0500
David Lechner [off-list ref] wrote:

On 7/27/24 8:15 AM, Jonathan Cameron wrote:

quoted

On Mon, 22 Jul 2024 16:57:09 -0500
David Lechner [off-list ref] wrote:
  

quoted

quoted

+/**
+ * spi_offload_prepare - prepare offload hardware for a transfer
+ * @spi:	The spi device to use for the transfers.
+ * @id:		Function ID if SPI device uses more than one offload or NULL.
+ * @msg:	The SPI message to use for the offload operation.
+ *
+ * Requests an offload instance with the specified ID and programs it with the
+ * provided message.
+ *
+ * The message must not be pre-optimized (do not call spi_optimize_message() on
+ * the message).
+ *
+ * Calls must be balanced with spi_offload_unprepare().
+ *
+ * Return: 0 on success, else a negative error code.
+ */
+int spi_offload_prepare(struct spi_device *spi, const char *id,
+			struct spi_message *msg)
+{
+	struct spi_controller *ctlr = spi->controller;
+	int ret;
+
+	if (!ctlr->offload_ops)
+		return -EOPNOTSUPP;
+
+	msg->offload = true;  

I'd set this later perhaps as...  

If we move it, then we would have to create a new function
to call instead of spi_optimize_message() so that the controller
driver can know that this is an offload message and not a
regular message since they will need to be handled differently
during the optimization phase.

Ah. I'd missed that.

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quoted

+
+	ret = spi_optimize_message(spi, msg);
+	if (ret)  

It otherwise needs clearing here so it doesn't have side
effects if an error occurs.

Then it needs clearing here I think.

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+		return ret;
+
+	mutex_lock(&ctlr->io_mutex);
+	ret = ctlr->offload_ops->prepare(spi, id, msg);
+	mutex_unlock(&ctlr->io_mutex);
+
+	if (ret) {
+		spi_unoptimize_message(msg);
+		msg->offload = false;
+		return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(spi_offload_prepare);