spi: core: added spi_resource management

SPI resource management framework used while processing a spi_message
via the spi-core.

The basic idea is taken from devres, but as the allocation may happen
fairly frequently, some provisioning (in the form of an unused spi_device
pointer argument to spi_res_alloc) has been made so that at a later stage
we may implement reuse objects allocated earlier avoiding the repeated
allocation by keeping a cache of objects that we can reuse.

This framework can get used for:
* rewriting spi_messages
  * to fullfill alignment requirements of the spi_master HW
  * to fullfill transfer length requirements
    (e.g: transfers need to be less than 64k)
  * consolidate spi_messages with multiple transfers into a single transfer
  when the total transfer length is below a threshold.
* reimplement spi_unmap_buf without explicitly needing to check if it has
  been mapped

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 91 insertions, 0 deletions

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 47eff8012a77..894ed0357dd7 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1024,6 +1024,8 @@ out:
 	if (msg->status && master->handle_err)
 		master->handle_err(master, msg);
 
+	spi_res_release(master, msg);
+
 	spi_finalize_current_message(master);
 
 	return ret;
@@ -2013,6 +2015,95 @@ struct spi_master *spi_busnum_to_master(u16 bus_num)
 }
 EXPORT_SYMBOL_GPL(spi_busnum_to_master);
 
+/*-------------------------------------------------------------------------*/
+
+/* Core methods for SPI resource management */
+
+/**
+ * spi_res_alloc - allocate a spi resource that is life-cycle managed
+ *                 during the processing of a spi_message while using
+ *                 spi_transfer_one
+ * @spi:     the spi device for which we allocate memory
+ * @release: the release code to execute for this resource
+ * @size:    size to alloc and return
+ * @gfp:     GFP allocation flags
+ *
+ * Return: the pointer to the allocated data
+ *
+ * This may get enhanced in the future to allocate from a memory pool
+ * of the @spi_device or @spi_master to avoid repeated allocations.
+ */
+void *spi_res_alloc(struct spi_device *spi,
+		    spi_res_release_t release,
+		    size_t size, gfp_t gfp)
+{
+	struct spi_res *sres;
+
+	sres = kzalloc(sizeof(*sres) + size, gfp);
+	if (!sres)
+		return NULL;
+
+	INIT_LIST_HEAD(&sres->entry);
+	sres->release = release;
+
+	return sres->data;
+}
+EXPORT_SYMBOL_GPL(spi_res_alloc);
+
+/**
+ * spi_res_free - free an spi resource
+ * @res: pointer to the custom data of a resource
+ *
+ */
+void spi_res_free(void *res)
+{
+	struct spi_res *sres = container_of(res, struct spi_res, data);
+
+	if (!res)
+		return;
+
+	WARN_ON(!list_empty(&sres->entry));
+	kfree(sres);
+}
+EXPORT_SYMBOL_GPL(spi_res_free);
+
+/**
+ * spi_res_add - add a spi_res to the spi_message
+ * @message: the spi message
+ * @res:     the spi_resource
+ */
+void spi_res_add(struct spi_message *message, void *res)
+{
+	struct spi_res *sres = container_of(res, struct spi_res, data);
+
+	WARN_ON(!list_empty(&sres->entry));
+	list_add_tail(&sres->entry, &message->resources);
+}
+EXPORT_SYMBOL_GPL(spi_res_add);
+
+/**
+ * spi_res_release - release all spi resources for this message
+ * @master:  the @spi_master
+ * @message: the @spi_message
+ */
+void spi_res_release(struct spi_master *master,
+		     struct spi_message *message)
+{
+	struct spi_res *res;
+
+	while (!list_empty(&message->resources)) {
+		res = list_last_entry(&message->resources,
+				      struct spi_res, entry);
+
+		if (res->release)
+			res->release(master, message, res->data);
+
+		list_del(&res->entry);
+
+		kfree(res);
+	}
+}
+EXPORT_SYMBOL_GPL(spi_res_release);
 
 /*-------------------------------------------------------------------------*/