linux-kernel - Re: [PATCH v3 1/3] soc: qcom: rpmpd: Allow RPMPD driver to be loaded as a module

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Message-ID: <20200414222158.GL576963@builder.lan>
Date:   Tue, 14 Apr 2020 15:21:58 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     John Stultz <john.stultz@...aro.org>
Cc:     lkml <linux-kernel@...r.kernel.org>, Todd Kjos <tkjos@...gle.com>,
        Saravana Kannan <saravanak@...gle.com>,
        Andy Gross <agross@...nel.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v3 1/3] soc: qcom: rpmpd: Allow RPMPD driver to be loaded
 as a module

On Thu 26 Mar 15:44 PDT 2020, John Stultz wrote:

> This patch allow the rpmpd driver to be loaded as a permenent
> module. Meaning it can be loaded from a module, but then cannot
> be unloaded.
> 
> Ideally, it would include a remove hook and related logic, but
> apparently the genpd code isn't able to track usage and cleaning
> things up? (See: https://lkml.org/lkml/2019/1/24/38)
> 
> So making it a permenent module at least improves things slightly
> over requiring it to be a built in driver.
> 
> Feedback would be appreciated!
> 
> Cc: Todd Kjos <tkjos@...gle.com>
> Cc: Saravana Kannan <saravanak@...gle.com>
> Cc: Andy Gross <agross@...nel.org>
> Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
> Cc: Rajendra Nayak <rnayak@...eaurora.org>
> Cc: linux-arm-msm@...r.kernel.org
> Acked-by: Saravana Kannan <saravanak@...gle.com>
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> ---
> v2:
> * Fix MODULE_LICENSE to be GPL v2 as suggested by Bjorn
> * Leave initcall as core_initcall, since that switches to module_initcall
>   only when built as a module, also suggested by Bjorn
> * Add module tags taken from Rajendra's earlier patch
> ---
>  drivers/soc/qcom/Kconfig | 4 ++--
>  drivers/soc/qcom/rpmpd.c | 6 ++++++
>  2 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/soc/qcom/Kconfig b/drivers/soc/qcom/Kconfig
> index d0a73e76d563..af774555b9d2 100644
> --- a/drivers/soc/qcom/Kconfig
> +++ b/drivers/soc/qcom/Kconfig
> @@ -123,8 +123,8 @@ config QCOM_RPMHPD
>  	  for the voltage rail.
>  
>  config QCOM_RPMPD
> -	bool "Qualcomm RPM Power domain driver"
> -	depends on QCOM_SMD_RPM=y
> +	tristate "Qualcomm RPM Power domain driver"
> +	depends on QCOM_SMD_RPM
>  	help
>  	  QCOM RPM Power domain driver to support power-domains with
>  	  performance states. The driver communicates a performance state
> diff --git a/drivers/soc/qcom/rpmpd.c b/drivers/soc/qcom/rpmpd.c
> index 2b1834c5609a..22fe94c03e79 100644
> --- a/drivers/soc/qcom/rpmpd.c
> +++ b/drivers/soc/qcom/rpmpd.c
> @@ -5,6 +5,7 @@
>  #include <linux/init.h>
>  #include <linux/kernel.h>
>  #include <linux/mutex.h>
> +#include <linux/module.h>

module comes before mutex in the alphabet.

>  #include <linux/pm_domain.h>
>  #include <linux/of.h>
>  #include <linux/of_device.h>
> @@ -226,6 +227,7 @@ static const struct of_device_id rpmpd_match_table[] = {
>  	{ .compatible = "qcom,qcs404-rpmpd", .data = &qcs404_desc },
>  	{ }
>  };
> +MODULE_DEVICE_TABLE(of, rpmpd_match_table);
>  
>  static int rpmpd_send_enable(struct rpmpd *pd, bool enable)
>  {
> @@ -422,3 +424,7 @@ static int __init rpmpd_init(void)
>  	return platform_driver_register(&rpmpd_driver);
>  }
>  core_initcall(rpmpd_init);
> +
> +MODULE_DESCRIPTION("Qualcomm Technologies, Inc. RPM Power Domain Driver");
> +MODULE_LICENSE("GPL v2");
> +MODULE_ALIAS("platform:qcom-rpmpd");

Is there any reason for this alias?

The module will be automatically loaded based on compatible and the
MODULE_DEVICE_TABLE() information above, and for ACPI would need a
similar acpi_device_id table.

Regards,
Bjorn

> -- 
> 2.17.1
>