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SubjectRE: [PATCH] Add driver to force WMI Thunderbolt controller power status
Date
> -----Original Message-----
> From: Mika Westerberg [mailto:mika.westerberg@linux.intel.com]
> Sent: Thursday, September 7, 2017 1:50 AM
> To: Limonciello, Mario <Mario_Limonciello@Dell.com>
> Cc: dvhart@infradead.org; LKML <linux-kernel@vger.kernel.org>; platform-driver-
> x86@vger.kernel.org; Richard Hughes <hughsient@gmail.com>; Yehezkel Bernat
> <yehezkelshb@gmail.com>
> Subject: Re: [PATCH] Add driver to force WMI Thunderbolt controller power status
>
> On Wed, Sep 06, 2017 at 12:54:00PM -0500, Mario Limonciello wrote:
> > Current implementations of Intel Thunderbolt controllers will go
> > into a low power mode when not in use.
> >
> > Many machines containing these controllers also have a GPIO wired up
> > that can force the controller awake. This is offered via a ACPI-WMI
> > interface intended to be manipulated by a userspace utility.
> >
> > This mechanism is provided by Intel to OEMs to include in BIOS.
> > It uses an industry wide GUID that is populated in a separate _WDG
> > entry with no binary MOF.
> >
> > This interface allow software such as fwupd to wake up thunderbolt
> > controllers to query the firmware version or flash new firmware.
> >
> > Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
> > ---
> > MAINTAINERS | 5 ++
> > drivers/platform/x86/Kconfig | 13 ++++
> > drivers/platform/x86/Makefile | 1 +
> > drivers/platform/x86/intel-wmi-thunderbolt.c | 97
> ++++++++++++++++++++++++++++
> > 4 files changed, 116 insertions(+)
> > create mode 100644 drivers/platform/x86/intel-wmi-thunderbolt.c
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 1c3feff..375bea9 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -3949,6 +3949,11 @@ M: Pali Rohár <pali.rohar@gmail.com>
> > S: Maintained
> > F: drivers/platform/x86/dell-wmi.c
> >
> > +INTEL WMI THUNDERBOLT DRIVER
> > +M: Mario Limonciello <mario.limonciello@dell.com>
> > +S: Maintained
> > +F: drivers/platform/x86/intel-wmi-thunderbolt.c
> > +
> > DELTA ST MEDIA DRIVER
> > M: Hugues Fruchet <hugues.fruchet@st.com>
> > L: linux-media@vger.kernel.org
> > diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
> > index 80b8795..6670a8d 100644
> > --- a/drivers/platform/x86/Kconfig
> > +++ b/drivers/platform/x86/Kconfig
> > @@ -658,6 +658,19 @@ config WMI_BMOF
> > To compile this driver as a module, choose M here: the module will
> > be called wmi-bmof.
> >
> > +config INTEL_WMI_THUNDERBOLT
> > + tristate "Intel WMI thunderbolt driver"
>
> "Intel WMI Thunderbolt force power driver"

Adjusted.

>
> > + depends on ACPI_WMI
> > + default ACPI_WMI
> > + ---help---
> > + Say Y here if you want to be able to use the WMI interface on select
> > + systems to force the power control of Intel Thunderbolt controllers.
> > + This is useful for updating the firmware when devices are not plugged
> > + into the controller.
> > +
> > + To compile this driver as a module, choose M here: the module will
> > + be called intel-wmi-thunderbolt.
> > +
> > config MSI_WMI
> > tristate "MSI WMI extras"
> > depends on ACPI_WMI
> > diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
> > index 91cec17..2b315d0 100644
> > --- a/drivers/platform/x86/Makefile
> > +++ b/drivers/platform/x86/Makefile
> > @@ -39,6 +39,7 @@ obj-$(CONFIG_PEAQ_WMI) += peaq-wmi.o
> > obj-$(CONFIG_SURFACE3_WMI) += surface3-wmi.o
> > obj-$(CONFIG_TOPSTAR_LAPTOP) += topstar-laptop.o
> > obj-$(CONFIG_WMI_BMOF) += wmi-bmof.o
> > +obj-$(CONFIG_INTEL_WMI_THUNDERBOLT) += intel-wmi-thunderbolt.o
> >
> > # toshiba_acpi must link after wmi to ensure that wmi devices are found
> > # before toshiba_acpi initializes
> > diff --git a/drivers/platform/x86/intel-wmi-thunderbolt.c
> b/drivers/platform/x86/intel-wmi-thunderbolt.c
> > new file mode 100644
> > index 0000000..98f60f2
> > --- /dev/null
> > +++ b/drivers/platform/x86/intel-wmi-thunderbolt.c
> > @@ -0,0 +1,97 @@
> > +/*
> > + * WMI Thunderbolt driver
> > + *
> > + * Copyright (C) 2017 Dell Inc. All Rights Reserved.
> > + *
> > + * This program is free software; you can redistribute it and/or modify it
> > + * under the terms of the GNU General Public License version 2 as published
> > + * by the Free Software Foundation.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> > + * GNU General Public License for more details.
> > + */
> > +
> > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> > +
> > +#include <linux/acpi.h>
> > +#include <linux/device.h>
> > +#include <linux/fs.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/string.h>
> > +#include <linux/sysfs.h>
> > +#include <linux/types.h>
> > +#include <linux/wmi.h>
> > +
> > +#define INTEL_WMI_THUNDERBOLT_GUID "86CCFD48-205E-4A77-9C48-
> 2021CBEDE341"
> > +
>
> Remove extra newline.

Removed.

>
> > +
> > +static ssize_t force_power_store(struct device *dev,
> > + struct device_attribute *attr,
> > + const char *buf, size_t count)
> > +{
> > + struct acpi_buffer input;
> > + acpi_status status;
> > + u8 mode;
> > +
> > + input.length = (acpi_size) (sizeof(u8));
>
> Is this cast really needed?

Nope, adjusted.

>
> > + input.pointer = &mode;
> > + mode = hex_to_bin(buf[0]);
> > + if (mode == 0 || mode == 1) {
> > + status = wmi_evaluate_method(INTEL_WMI_THUNDERBOLT_GUID,
> 0, 1,
> > + &input, NULL);
> > + if (ACPI_FAILURE(status)) {
> > + pr_err("intel-wmi-thunderbolt: failed setting %s\n",
> > + buf);
> > + return -ENODEV;
> > + }
> > + } else {
> > + pr_err("intel-wmi-thunderbolt: unsupported mode: %d", mode);
> > + }
> > + return count;
> > +}
> > +
> > +static DEVICE_ATTR_WO(force_power);
> > +
> > +static struct attribute *tbt_attrs[] = {
>
> Can this be const?

No, "initialization from incompatible pointer type" if set like that.
Other drivers in platform/ seem to follow the same approach too.

>
> > + &dev_attr_force_power.attr,
> > + NULL
> > +};
> > +
> > +static const struct attribute_group tbt_attribute_group = {
> > + .attrs = tbt_attrs,
> > +};
> > +
> > +static int intel_wmi_thunderbolt_probe(struct wmi_device *wdev)
> > +{
> > + return sysfs_create_group(&wdev->dev.kobj, &tbt_attribute_group);
>
> You need to document this in Documentation/ABI. While there, I think it
> make sense to update Documentation/admin-guide/thunderbolt.rst
> accordingly.
>

Thanks, will fix for v2.

> Also you are adding an attribute to a device that is already announced
> to the userspace (I think). So it is possible userspace does not find
> this when it deals with the uevent. Not sure if it is really a problem
> in this case, though.
>

I don't think it will matter in this case. It will come down to how fwupd
decides to use this (which will be TBD and is under discussion still).

> Other than that, looks nice to me :)

Thanks for your feedback. I'll send a follow up v2 in a few moments.

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