Re: [PATCH] platform/x86: dell-dw5826e: Add reset driver for DW5826e

[Ilpo Järvinen]

On Wed, 8 Apr 2026, Jack Wu wrote:

> If the DW5826e is in a frozen state and unable to receive USB commands,
> this driver provides a method for the user to reset the DW5826e via ACPI.
> 
> Signed-off-by: Jack Wu <jackbb_wu@xxxxxxxxxx>
> ---
>  drivers/platform/x86/dell/Kconfig             |   6 +
>  drivers/platform/x86/dell/Makefile            |   2 +
>  .../platform/x86/dell/dell-dw5826e-reset.c    | 120 ++++++++++++++++++
>  3 files changed, 128 insertions(+)
>  create mode 100644 drivers/platform/x86/dell/dell-dw5826e-reset.c
> 
> diff --git a/drivers/platform/x86/dell/Kconfig b/drivers/platform/x86/dell/Kconfig
> index 738c108c2163..c4540c837a88 100644
> --- a/drivers/platform/x86/dell/Kconfig
> +++ b/drivers/platform/x86/dell/Kconfig
> @@ -276,4 +276,10 @@ config DELL_WMI_SYSMAN
>  	  To compile this driver as a module, choose M here: the module will
>  	  be called dell-wmi-sysman.
>  
> +config DELL_DW5826E_RESET
> +	tristate "Dell DW5826e PLDR reset support"
> +	default m
> +	depends on ACPI
> +	help
> +	  This adds support for the Dell DW5826e PLDR reset via ACPI
>  endif # X86_PLATFORM_DRIVERS_DELL
> diff --git a/drivers/platform/x86/dell/Makefile b/drivers/platform/x86/dell/Makefile
> index c7501c25e627..8150283cfd1d 100644
> --- a/drivers/platform/x86/dell/Makefile
> +++ b/drivers/platform/x86/dell/Makefile
> @@ -28,3 +28,5 @@ obj-$(CONFIG_DELL_WMI_DESCRIPTOR)		+= dell-wmi-descriptor.o
>  obj-$(CONFIG_DELL_WMI_DDV)			+= dell-wmi-ddv.o
>  obj-$(CONFIG_DELL_WMI_LED)			+= dell-wmi-led.o
>  obj-$(CONFIG_DELL_WMI_SYSMAN)			+= dell-wmi-sysman/
> +obj-$(CONFIG_DELL_DW5826E_RESET)		+= dell-dw5826e-reset.o

Another thing,

I wonder if this is good place for this, as kernel also has drivers/reset/.

-- 
 i.

> +
> diff --git a/drivers/platform/x86/dell/dell-dw5826e-reset.c b/drivers/platform/x86/dell/dell-dw5826e-reset.c
> new file mode 100644
> index 000000000000..28865a123c63
> --- /dev/null
> +++ b/drivers/platform/x86/dell/dell-dw5826e-reset.c
> @@ -0,0 +1,120 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + *  dell-dw5826e-reset.c - Dell DW5826e reset driver
> + *
> + *  Copyright (C) 2026 Jackbb Wu <jackbb.wu@xxxxxxxxxx>
> + *
> + */
> +
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/acpi.h>
> +#include <linux/miscdevice.h>
> +#include <linux/fs.h>
> +#include <linux/uaccess.h>
> +
> +static guid_t palc_dsm_guid =
> +	GUID_INIT(0x5a1a4bba, 0x8006, 0x487e, 0xbe, 0x0a, 0xac, 0xf5, 0xd8, 0xfd, 0xfe, 0x59);
> +
> +struct palc_dev {
> +	struct device *dev;
> +	acpi_handle handle;
> +	struct miscdevice miscdev;
> +};
> +
> +static int trigger_palc_pldr(struct palc_dev *palc)
> +{
> +	union acpi_object *obj;
> +
> +	dev_info(palc->dev, "Triggering PLDR via ACPI _DSM Function 1...\n");
> +
> +	obj = acpi_evaluate_dsm(palc->handle, &palc_dsm_guid, 1, 1, NULL);
> +
> +	if (!obj) {
> +		dev_err(palc->dev, "Failed to evaluate _DSM\n");
> +		return -EIO;
> +	}
> +
> +	if (obj->type == ACPI_TYPE_BUFFER)
> +		dev_info(palc->dev, "PLDR _DSM executed successfully\n");
> +
> +	ACPI_FREE(obj);
> +	return 0;
> +}
> +
> +static ssize_t palc_write(struct file *filp, const char __user *buf, size_t count, loff_t *ppos)
> +{
> +	struct palc_dev *palc = filp->private_data;
> +
> +	trigger_palc_pldr(palc);
> +
> +	return count;
> +}
> +
> +static int palc_open(struct inode *inode, struct file *filp)
> +{
> +	struct palc_dev *palc = container_of(filp->private_data, struct palc_dev, miscdev);
> +
> +	filp->private_data = palc;
> +	return 0;
> +}
> +
> +static const struct file_operations palc_fops = {
> +	.owner  = THIS_MODULE,
> +	.open   = palc_open,
> +	.write  = palc_write,
> +};
> +
> +static int palc_acpi_probe(struct acpi_device *adev)
> +{
> +	struct palc_dev *palc;
> +
> +	palc = devm_kzalloc(&adev->dev, sizeof(*palc), GFP_KERNEL);
> +	if (!palc)
> +		return -ENOMEM;
> +
> +	palc->dev    = &adev->dev;
> +	palc->handle = adev->handle;
> +
> +	palc->miscdev.minor  = MISC_DYNAMIC_MINOR;
> +	palc->miscdev.name   = "reset_palc";
> +	palc->miscdev.fops   = &palc_fops;
> +	palc->miscdev.parent = &adev->dev;
> +
> +	if (misc_register(&palc->miscdev))
> +		return -EINVAL;
> +
> +	dev_set_drvdata(&adev->dev, palc);
> +
> +	dev_info(&adev->dev, "DW5826e Reset Device (PALC0001) Driver Loaded\n");
> +	return 0;
> +}
> +
> +static void palc_acpi_remove(struct acpi_device *adev)
> +{
> +	struct palc_dev *palc = dev_get_drvdata(&adev->dev);
> +
> +	if (palc)
> +		misc_deregister(&palc->miscdev);
> +}
> +
> +static const struct acpi_device_id palc_acpi_ids[] = {
> +	{ "PALC0001", 0 },
> +	{ "", 0 }
> +};
> +
> +static struct acpi_driver palc_acpi_driver = {
> +	.name  = "palc_reset",
> +	.ids   = palc_acpi_ids,
> +	.ops = {
> +		.add    = palc_acpi_probe,
> +		.remove = palc_acpi_remove,
> +	},
> +};
> +
> +MODULE_DEVICE_TABLE(acpi, palc_acpi_ids);
> +module_acpi_driver(palc_acpi_driver);
> +
> +MODULE_DESCRIPTION("Dell DW5826e reset driver");
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("JackBB Wu");
>