On Thu, Jan 07, 2021 at 09:28:37AM -0500, Thara Gopinath wrote:

On 1/6/21 3:15 PM, Cristian Marussi wrote:

quoted

Expose to the SCMI drivers a new devres managed common protocols API based
on generic get/put methods and protocol handles.

All drivers still keep using the old API, no functional change.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
---
  drivers/firmware/arm_scmi/driver.c | 92 ++++++++++++++++++++++++++++++
  include/linux/scmi_protocol.h      | 11 ++++
  2 files changed, 103 insertions(+)

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 10fe9aacae1b..fbc3ba1b69f6 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c

@@ -15,6 +15,7 @@
   */
  #include <linux/bitmap.h>
+#include <linux/device.h>
  #include <linux/export.h>
  #include <linux/idr.h>
  #include <linux/io.h>

@@ -732,6 +733,95 @@ scmi_is_protocol_implemented(const struct scmi_handle *handle, u8 prot_id)
  	return false;
  }
+struct scmi_protocol_devres {
+	struct scmi_handle *handle;
+	u8 protocol_id;
+};
+
+static void scmi_devm_release_protocol(struct device *dev, void *res)
+{
+	struct scmi_protocol_devres *dres = res;
+
+	scmi_release_protocol(dres->handle, dres->protocol_id);
+}
+
+/**
+ * scmi_devm_get_protocol_ops  - Devres managed get protocol operations
+ * @sdev: A reference to an scmi_device whose embedded struct device is to
+ *	  be used for devres accounting.
+ * @protocol_id: The protocol being requested.
+ * @ph: A pointer reference used to pass back the associated protocol handle.
+ *
+ * Get hold of a protocol accounting for its usage, eventually triggering its
+ * initialization, and returning the protocol specific operations and related
+ * protocol handle which will be used as first argument in most of the
+ * protocols operations methods.
+ * Being a devres based managed method, protocol hold will be automatically
+ * released, and possibly de-initialized on last user, once the SCMI driver
+ * owning the scmi_device is unbound from it.
+ *
+ * Return: A reference to the requested protocol operations or error.
+ *	   Must be checked for errors by caller.
+ */
+static const void __must_check *
+scmi_devm_get_protocol_ops(struct scmi_device *sdev, u8 protocol_id,
+			   struct scmi_protocol_handle **ph)
+{
+	struct scmi_protocol_instance *pi;
+	struct scmi_protocol_devres *dres;
+	struct scmi_handle *handle = sdev->handle;
+
+	if (!ph)
+		return ERR_PTR(-EINVAL);
+
+	dres = devres_alloc(scmi_devm_release_protocol,
+			    sizeof(*dres), GFP_KERNEL);
+	if (!dres)
+		return ERR_PTR(-ENOMEM);
+
+	pi = scmi_get_protocol_instance(handle, protocol_id);
+	if (IS_ERR(pi)) {
+		devres_free(dres);
+		return pi;
+	}
+
+	dres->handle = handle;
+	dres->protocol_id = protocol_id;
+	devres_add(&sdev->dev, dres);
+
+	*ph = &pi->ph;
+
+	return pi->proto->ops;
+}
+
+static int scmi_devm_protocol_match(struct device *dev, void *res, void *data)
+{
+	struct scmi_protocol_devres *dres = res;
+
+	if (WARN_ON(!dres || !data))
+		return 0;
+
+	return dres->protocol_id == *((u8 *)data);
+}
+
+/**
+ * scmi_devm_put_protocol_ops  - Devres managed put protocol operations
+ * @sdev: A reference to an scmi_device whose embedded struct device is to
+ *	  be used for devres accounting.
+ * @protocol_id: The protocol being requested.
+ *
+ * Explicitly release a protocol hold previously obtained calling the above
+ * @scmi_devm_get_protocol_ops.
+ */
+static void scmi_devm_put_protocol_ops(struct scmi_device *sdev, u8 protocol_id)
+{
+	int ret;
+
+	ret = devres_release(&sdev->dev, scmi_devm_release_protocol,
+			     scmi_devm_protocol_match, &protocol_id);
+	WARN_ON(ret);
+}
+
  /**
   * scmi_handle_get() - Get the SCMI handle for a device
   *

@@ -986,6 +1076,8 @@ static int scmi_probe(struct platform_device *pdev)
  	handle = &info->handle;
  	handle->dev = info->dev;
  	handle->version = &info->version;
+	handle->devm_get_ops = scmi_devm_get_protocol_ops;
+	handle->devm_put_ops = scmi_devm_put_protocol_ops;
  	ret = scmi_txrx_setup(info, dev, SCMI_PROTOCOL_BASE);
  	if (ret)

diff --git a/include/linux/scmi_protocol.h b/include/linux/scmi_protocol.h
index 757a826e3cef..2fd2fffb4024 100644
--- a/include/linux/scmi_protocol.h
+++ b/include/linux/scmi_protocol.h

@@ -57,6 +57,8 @@ struct scmi_clock_info {
  };
  struct scmi_handle;
+struct scmi_device;
+struct scmi_protocol_handle;
  /**
   * struct scmi_clk_ops - represents the various operations provided

@@ -593,6 +595,9 @@ struct scmi_notify_ops {
   * @sensor_ops: pointer to set of sensor protocol operations
   * @reset_ops: pointer to set of reset protocol operations
   * @voltage_ops: pointer to set of voltage protocol operations
+ * @devm_get_ops: devres managed method to acquire a protocol and get specific
+ *		  operations and a dedicated protocol handler
+ * @devm_put_ops: devres managed method to release a protocol
   * @notify_ops: pointer to set of notifications related operations
   * @perf_priv: pointer to private data structure specific to performance
   *	protocol(for internal use only)

@@ -618,6 +623,12 @@ struct scmi_handle {
  	const struct scmi_sensor_ops *sensor_ops;
  	const struct scmi_reset_ops *reset_ops;
  	const struct scmi_voltage_ops *voltage_ops;
+
+	const void __must_check *
+		(*devm_get_ops)(struct scmi_device *sdev, u8 proto,
+				struct scmi_protocol_handle **ph);
+	void (*devm_put_ops)(struct scmi_device *sdev, u8 proto);

These names are misleading. The devm_get_ops does two things. One populate
the scmi_protocol_handle, second return the protocol ops. Either split this
into two separate functions or rename it into something like
devm_get_protocol (or something better). Similar comment for devm_put_ops as
there is no releasing of ops happening here per say.

Yes I agree, now that you really get ops and a hold on the protocol in
fact it'd be better _get_protocol/_put_protocol or similar; I'd prefer
not to split retrieving the ops from the protocol_handle since they
need each other to work. I'll fix in V5.

Also I am still not convinced that protocol_instance should be hidden from
the client drivers. But if everyone else is aligned towards this approach, I
am fine.

Do you mean passing the protocol_handle around instead of the handle, so
that protocols impementation are restricted to their own protocol number
and SCMI drivers cannot access anything at the protocol layer ?
It seems reasonable to me but I'm happy to discuss your concerns, also
because up until now you are my main and only feedback about this :D

Thanks

Cristian

quoted

+
  	const struct scmi_notify_ops *notify_ops;
  	/* for protocol internal use */
  	void *perf_priv;

-- 
Warm Regards
Thara

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