[PATCH v2] platform/x86: dell-dw5826e: Add reset driver for DW5826e

[PATCH v2] platform/x86: dell-dw5826e: Add reset driver for DW5826e

[Jack Wu]

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.

E.g: echo 1 > /sys/bus/platform/devices/PALC0001\:00/pldr

Signed-off-by: Jack Wu <jackbb_wu@compal.com>
---
v2:
  - Remove extra empty line
  - Add missing includes and Remove unnecessary includes, sort includes alphabetically
  - Remove noisy dev_info()
  - Handle obj->type != ACPI_TYPE_BUFFER as error with proper return code
  - Replace miscdevice/file_operations with sysfs attribute (DEVICE_ATTR_WO) to reduce boilerplate
  - Propagate trigger_palc_pldr() return code to userspace
  - Convert from acpi_driver to platform_driver
---
---
 drivers/platform/x86/dell/Kconfig             |  6 ++
 drivers/platform/x86/dell/Makefile            |  2 +
 .../platform/x86/dell/dell-dw5826e-reset.c    | 83 +++++++++++++++++++
 3 files changed, 91 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
+
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..52002578ed68
--- /dev/null
+++ b/drivers/platform/x86/dell/dell-dw5826e-reset.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  dell-dw5826e-reset.c - Dell DW5826e reset driver
+ *
+ *  Copyright (C) 2026 Jackbb Wu <jackbb.wu@compal.com>
+ */
+
+#include <linux/acpi.h>
+#include <linux/device.h>
+#include <linux/uuid.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+
+static guid_t palc_dsm_guid =
+	GUID_INIT(0x5a1a4bba, 0x8006, 0x487e, 0xbe, 0x0a, 0xac, 0xf5, 0xd8, 0xfd, 0xfe, 0x59);
+
+static int trigger_palc_pldr(struct device *dev, acpi_handle handle)
+{
+	union acpi_object *obj;
+	int ret = 0;
+
+	obj = acpi_evaluate_dsm(handle, &palc_dsm_guid, 1, 1, NULL);
+	if (!obj) {
+		dev_err(dev, "Failed to evaluate _DSM\n");
+		return -EIO;
+	}
+
+	if (obj->type != ACPI_TYPE_BUFFER) {
+		dev_err(dev, "Unexpected _DSM return type: %d\n", obj->type);
+		ret = -EINVAL;
+	}
+
+	ACPI_FREE(obj);
+	return ret;
+}
+
+static ssize_t pldr_store(struct device *dev, struct device_attribute *attr,
+			  const char *buf, size_t count)
+{
+	acpi_handle handle = ACPI_HANDLE(dev);
+	int ret;
+
+	ret = trigger_palc_pldr(dev, handle);
+	if (ret)
+		return ret;
+
+	return count;
+}
+static DEVICE_ATTR_WO(pldr);
+
+static struct attribute *palc_attrs[] = {
+	&dev_attr_pldr.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(palc);
+
+static int palc_probe(struct platform_device *pdev)
+{
+	if (!ACPI_HANDLE(&pdev->dev))
+		return -ENODEV;
+
+	return 0;
+}
+
+static const struct acpi_device_id palc_acpi_ids[] = {
+	{ "PALC0001", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(acpi, palc_acpi_ids);
+
+static struct platform_driver palc_driver = {
+	.driver = {
+		.name = "dell-dw5826e-reset",
+		.acpi_match_table = palc_acpi_ids,
+		.dev_groups = palc_groups,
+	},
+	.probe  = palc_probe,
+};
+module_platform_driver(palc_driver);
+
+MODULE_DESCRIPTION("Dell DW5826e reset driver");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("JackBB Wu");
-- 
2.34.1

Re: [PATCH v2] platform/x86: dell-dw5826e: Add reset driver for DW5826e

[Mario Limonciello]

On 4/10/26 04:37, Jack Wu wrote:
> [You don't often get email from wojackbb@gmail.com. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> 
> 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.
> 
> E.g: echo 1 > /sys/bus/platform/devices/PALC0001\:00/pldr
> 
> Signed-off-by: Jack Wu <jackbb_wu@compal.com>
> ---
> v2:
>    - Remove extra empty line
>    - Add missing includes and Remove unnecessary includes, sort includes alphabetically
>    - Remove noisy dev_info()
>    - Handle obj->type != ACPI_TYPE_BUFFER as error with proper return code
>    - Replace miscdevice/file_operations with sysfs attribute (DEVICE_ATTR_WO) to reduce boilerplate
>    - Propagate trigger_palc_pldr() return code to userspace
>    - Convert from acpi_driver to platform_driver
> ---

Generally speaking this looks much better.  The only thing missing to me 
is documentation to go with it since it won't be obvious to a user what 
the "pldr" sysfs file represents.

Also in that sense - if the ACPI PALC0001 device will always represent 
WWAN reset, then maybe the sysfs file should also be called wwan_reset 
instead of pldr (platform device reset).

> ---
>   drivers/platform/x86/dell/Kconfig             |  6 ++
>   drivers/platform/x86/dell/Makefile            |  2 +
>   .../platform/x86/dell/dell-dw5826e-reset.c    | 83 +++++++++++++++++++
>   3 files changed, 91 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
> +
> 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..52002578ed68
> --- /dev/null
> +++ b/drivers/platform/x86/dell/dell-dw5826e-reset.c
> @@ -0,0 +1,83 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + *  dell-dw5826e-reset.c - Dell DW5826e reset driver
> + *
> + *  Copyright (C) 2026 Jackbb Wu <jackbb.wu@compal.com>
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/device.h>
> +#include <linux/uuid.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +
> +static guid_t palc_dsm_guid =
> +       GUID_INIT(0x5a1a4bba, 0x8006, 0x487e, 0xbe, 0x0a, 0xac, 0xf5, 0xd8, 0xfd, 0xfe, 0x59);
> +
> +static int trigger_palc_pldr(struct device *dev, acpi_handle handle)
> +{
> +       union acpi_object *obj;
> +       int ret = 0;
> +
> +       obj = acpi_evaluate_dsm(handle, &palc_dsm_guid, 1, 1, NULL);
> +       if (!obj) {
> +               dev_err(dev, "Failed to evaluate _DSM\n");
> +               return -EIO;
> +       }
> +
> +       if (obj->type != ACPI_TYPE_BUFFER) {
> +               dev_err(dev, "Unexpected _DSM return type: %d\n", obj->type);
> +               ret = -EINVAL;
> +       }
> +
> +       ACPI_FREE(obj);
> +       return ret;
> +}
> +
> +static ssize_t pldr_store(struct device *dev, struct device_attribute *attr,
> +                         const char *buf, size_t count)
> +{
> +       acpi_handle handle = ACPI_HANDLE(dev);
> +       int ret;
> +
> +       ret = trigger_palc_pldr(dev, handle);
> +       if (ret)
> +               return ret;
> +
> +       return count;
> +}
> +static DEVICE_ATTR_WO(pldr);
> +
> +static struct attribute *palc_attrs[] = {
> +       &dev_attr_pldr.attr,
> +       NULL
> +};
> +ATTRIBUTE_GROUPS(palc);
> +
> +static int palc_probe(struct platform_device *pdev)
> +{
> +       if (!ACPI_HANDLE(&pdev->dev))
> +               return -ENODEV;
> +
> +       return 0;
> +}
> +
> +static const struct acpi_device_id palc_acpi_ids[] = {
> +       { "PALC0001", 0 },
> +       { }
> +};
> +MODULE_DEVICE_TABLE(acpi, palc_acpi_ids);
> +
> +static struct platform_driver palc_driver = {
> +       .driver = {
> +               .name = "dell-dw5826e-reset",
> +               .acpi_match_table = palc_acpi_ids,
> +               .dev_groups = palc_groups,
> +       },
> +       .probe  = palc_probe,
> +};
> +module_platform_driver(palc_driver);
> +
> +MODULE_DESCRIPTION("Dell DW5826e reset driver");
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("JackBB Wu");
> --
> 2.34.1
> 
> 

Re: [PATCH v2] platform/x86: dell-dw5826e: Add reset driver for DW5826e

[Armin Wolf]

Am 10.04.26 um 11:37 schrieb Jack Wu:
> 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.
> 
> E.g: echo 1 > /sys/bus/platform/devices/PALC0001\:00/pldr
> 
> Signed-off-by: Jack Wu <jackbb_wu@compal.com>
> ---
> v2:
>    - Remove extra empty line
>    - Add missing includes and Remove unnecessary includes, sort includes alphabetically
>    - Remove noisy dev_info()
>    - Handle obj->type != ACPI_TYPE_BUFFER as error with proper return code
>    - Replace miscdevice/file_operations with sysfs attribute (DEVICE_ATTR_WO) to reduce boilerplate
>    - Propagate trigger_palc_pldr() return code to userspace
>    - Convert from acpi_driver to platform_driver
> ---
> ---
>   drivers/platform/x86/dell/Kconfig             |  6 ++
>   drivers/platform/x86/dell/Makefile            |  2 +
>   .../platform/x86/dell/dell-dw5826e-reset.c    | 83 +++++++++++++++++++
>   3 files changed, 91 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
> +
> 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..52002578ed68
> --- /dev/null
> +++ b/drivers/platform/x86/dell/dell-dw5826e-reset.c
> @@ -0,0 +1,83 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + *  dell-dw5826e-reset.c - Dell DW5826e reset driver
> + *
> + *  Copyright (C) 2026 Jackbb Wu <jackbb.wu@compal.com>
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/device.h>
> +#include <linux/uuid.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +
> +static guid_t palc_dsm_guid =
> +	GUID_INIT(0x5a1a4bba, 0x8006, 0x487e, 0xbe, 0x0a, 0xac, 0xf5, 0xd8, 0xfd, 0xfe, 0x59);
> +
> +static int trigger_palc_pldr(struct device *dev, acpi_handle handle)
> +{
> +	union acpi_object *obj;
> +	int ret = 0;
> +
> +	obj = acpi_evaluate_dsm(handle, &palc_dsm_guid, 1, 1, NULL);
> +	if (!obj) {
> +		dev_err(dev, "Failed to evaluate _DSM\n");
> +		return -EIO;
> +	}
> +
> +	if (obj->type != ACPI_TYPE_BUFFER) {
> +		dev_err(dev, "Unexpected _DSM return type: %d\n", obj->type);
> +		ret = -EINVAL;
> +	}
> +
> +	ACPI_FREE(obj);
> +	return ret;
> +}
> +
> +static ssize_t pldr_store(struct device *dev, struct device_attribute *attr,
> +			  const char *buf, size_t count)
> +{
> +	acpi_handle handle = ACPI_HANDLE(dev);
> +	int ret;
> +
> +	ret = trigger_palc_pldr(dev, handle);
> +	if (ret)
> +		return ret;
> +
> +	return count;
> +}
> +static DEVICE_ATTR_WO(pldr);
> +
> +static struct attribute *palc_attrs[] = {
> +	&dev_attr_pldr.attr,
> +	NULL
> +};
> +ATTRIBUTE_GROUPS(palc);
> +
> +static int palc_probe(struct platform_device *pdev)
> +{
> +	if (!ACPI_HANDLE(&pdev->dev))
> +		return -ENODEV;
> +

Hi, please check here if the _DSM method exists using acpi_check_dsm().

Thanks,
Armin Wolf

> +	return 0;
> +}
> +
> +static const struct acpi_device_id palc_acpi_ids[] = {
> +	{ "PALC0001", 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(acpi, palc_acpi_ids);
> +
> +static struct platform_driver palc_driver = {
> +	.driver = {
> +		.name = "dell-dw5826e-reset",
> +		.acpi_match_table = palc_acpi_ids,
> +		.dev_groups = palc_groups,
> +	},
> +	.probe  = palc_probe,
> +};
> +module_platform_driver(palc_driver);
> +
> +MODULE_DESCRIPTION("Dell DW5826e reset driver");
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("JackBB Wu");