Re: [PATCH v3 updated 3/3] ACPI / PMIC: AXP288: support virtual GPIO in ACPI table

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

On Monday, November 24, 2014 05:32:33 PM Aaron Lu wrote:
> On 11/24/2014 09:06 AM, Rafael J. Wysocki wrote:
> > On Friday, November 21, 2014 03:11:51 PM Aaron Lu wrote:
> >> +	if (!result) {
> >> +		status = acpi_install_address_space_handler(
> >> +				ACPI_HANDLE(parent), ACPI_ADR_SPACE_GPIO,
> >> +				intel_xpower_pmic_gpio_handler, NULL, NULL);
> > 
> > So here we have a problem, because we can't unregister the opregion handler
> > registered above if this fails.  Not nice.
> 
> I'm not correct in the cover letter, the actual problem with operation
> region remove is with module unload, it happens like this:
> 
> The acpi_remove_address_space_handler doesn't wait for the current
> running handler to return, so if we call
> acpi_remove_address_space_handler in a module's exit function, the
> handler's memory will be freed and the running handler will access to
> a no longer valid memory place.
> 
> So as long as we can make sure the handler will not go away from the
> memory, we are safe.

This only means that address space handlers cannot be removed from kernel
modules.

Lv was trying to add a wrapper for that some time ago, maybe it's a good
idea to revive that?

> With this said, the updated patch is here:
> 
> From: Aaron Lu <aaron.lu@intel.com>
> Date: Mon, 20 Oct 2014 17:06:20 +0800
> Subject: [PATCH 3/3] ACPI / PMIC: AXP288: support virtual GPIO in ACPI table
> 
> The same virtual GPIO strategy is also used for the AXP288 PMIC in that
> various control methods that are used to do power rail handling and
> sensor reading/setting will touch GPIO fields defined under the PMIC
> device. The GPIO fileds are only defined by the ACPI code while the
> actual hardware doesn't really have a GPIO controller, but to make those
> control method execution succeed, we have to install a GPIO handler for
> the PMIC device handle. Since we do not need the virtual GPIO strategy,
> we can simply do nothing in that handler.
> 
> Signed-off-by: Aaron Lu <aaron.lu@intel.com>
> ---
>  drivers/acpi/pmic/intel_pmic_xpower.c | 30 ++++++++++++++++++++++++++----
>  1 file changed, 26 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/acpi/pmic/intel_pmic_xpower.c b/drivers/acpi/pmic/intel_pmic_xpower.c
> index 795ca073db08..9ec57ebd81c9 100644
> --- a/drivers/acpi/pmic/intel_pmic_xpower.c
> +++ b/drivers/acpi/pmic/intel_pmic_xpower.c
> @@ -220,13 +220,35 @@ static struct intel_pmic_opregion_data intel_xpower_pmic_opregion_data = {
>  	.thermal_table_count = ARRAY_SIZE(thermal_table),
>  };
>  
> +static acpi_status intel_xpower_pmic_gpio_handler(u32 function,
> +		acpi_physical_address address, u32 bit_width, u64 *value,
> +		void *handler_context, void *region_context)
> +{
> +	return AE_OK;
> +}
>  
>  static int intel_xpower_pmic_opregion_probe(struct platform_device *pdev)
>  {
> -	struct axp20x_dev *axp20x = dev_get_drvdata(pdev->dev.parent);
> -	return intel_pmic_install_opregion_handler(&pdev->dev,
> -			ACPI_HANDLE(pdev->dev.parent), axp20x->regmap,
> -			&intel_xpower_pmic_opregion_data);
> +	struct device *parent = pdev->dev.parent;
> +	struct axp20x_dev *axp20x = dev_get_drvdata(parent);
> +	acpi_status status;
> +	int result;
> +
> +	status = acpi_install_address_space_handler(ACPI_HANDLE(parent),
> +			ACPI_ADR_SPACE_GPIO, intel_xpower_pmic_gpio_handler,
> +			NULL, NULL);
> +	if (ACPI_FAILURE(status))
> +		return -ENODEV;
> +
> +	result = intel_pmic_install_opregion_handler(&pdev->dev,
> +					ACPI_HANDLE(parent), axp20x->regmap,
> +					&intel_xpower_pmic_opregion_data);
> +	if (result)
> +		acpi_remove_address_space_handler(ACPI_HANDLE(parent),
> +						  ACPI_ADR_SPACE_GPIO,
> +						  intel_xpower_pmic_gpio_handler);
> +
> +	return result;
>  }
>  
>  static struct platform_driver intel_xpower_pmic_opregion_driver = {
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.