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Message-ID: <e817b8a6-6e67-9f1e-8541-5e0b15d7a562@linaro.org>
Date: Thu, 7 Jan 2021 09:28:37 -0500
From: Thara Gopinath <thara.gopinath@...aro.org>
To: Cristian Marussi <cristian.marussi@....com>,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc: sudeep.holla@....com, lukasz.luba@....com,
james.quinlan@...adcom.com, Jonathan.Cameron@...wei.com,
f.fainelli@...il.com, etienne.carriere@...aro.org,
vincent.guittot@...aro.org, souvik.chakravarty@....com
Subject: Re: [PATCH v4 03/37] firmware: arm_scmi: introduce devres get/put
protocols operations
On 1/6/21 3:15 PM, Cristian Marussi wrote:
> 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@....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.
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.
> +
> const struct scmi_notify_ops *notify_ops;
> /* for protocol internal use */
> void *perf_priv;
>
--
Warm Regards
Thara
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