Message-ID: <CAFqHKT=6iKG4UmF2-PUESCDDnLcgzon5Z3UqJd+vNrXLXf9CSQ@mail.gmail.com>
Date: Wed, 2 Apr 2025 13:47:11 -0700
From: Derek John Clark <derekjohn.clark@...il.com>
To: Armin Wolf <W_Armin@....de>
Cc: Hans de Goede <hdegoede@...hat.com>, Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>, 
	Jonathan Corbet <corbet@....net>, Mario Limonciello <superm1@...nel.org>, Luke Jones <luke@...nes.dev>, 
	Xino Ni <nijs1@...ovo.com>, Zhixin Zhang <zhangzx36@...ovo.com>, Mia Shao <shaohz1@...ovo.com>, 
	Mark Pearson <mpearson-lenovo@...ebb.ca>, 
	"Pierre-Loup A . Griffais" <pgriffais@...vesoftware.com>, "Cody T . -H . Chiu" <codyit@...il.com>, 
	John Martens <johnfanv2@...il.com>, platform-driver-x86@...r.kernel.org, 
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 4/6 RESEND] platform/x86: Add Lenovo Capability Data 01
 WMI Driver

On Wed, Mar 26, 2025 at 6:29 PM Armin Wolf <W_Armin@....de> wrote:
>
> Am 17.03.25 um 15:43 schrieb Derek J. Clark:
>
> > Adds lenovo-wmi-capdata01 driver which provides the
> > LENOVO_CAPABILITY_DATA_01 WMI data block that comes on "Other Mode"
> > enabled hardware. Provides an interface for querying if a given
> > attribute is supported by the hardware, as well as its default_value,
> > max_value, min_value, and step increment.
> >
> > Signed-off-by: Derek J. Clark <derekjohn.clark@...il.com>
> > ---
> > v4:
> >   - Make driver data a private struct, remove references from Other Mode
> >     driver.
> >   - Don't cache data at device initialization. Instead, on component bind,
> >     cache the data on a member variable of the Other Mode driver data
> >     passed as a void pointer.
> >   - Add header file for capdata01 structs.
> >   - Add new struct to pass capdata01 array data and array length to Other
> >     Mode.
> > v3:
> > - Add as component to lenovo-wmi-other driver.
> > v2:
> > - Use devm_kmalloc to ensure driver can be instanced, remove global
> >    reference.
> > - Ensure reverse Christmas tree for all variable declarations.
> > - Remove extra whitespace.
> > - Use guard(mutex) in all mutex instances, global mutex.
> > - Use pr_fmt instead of adding the driver name to each pr_err.
> > - Remove noisy pr_info usage.
> > - Rename capdata_wmi to lenovo_wmi_cd01_priv and cd01_wmi to priv.
> > - Use list to get the lenovo_wmi_cd01_priv instance in
> >    lenovo_wmi_capdata01_get as none of the data provided by the macros
> >    that will use it can pass a member of the struct for use in
> >    container_of.
> > ---
> >   MAINTAINERS                                 |   2 +
> >   drivers/platform/x86/Kconfig                |   4 +
> >   drivers/platform/x86/Makefile               |   1 +
> >   drivers/platform/x86/lenovo-wmi-capdata01.c | 136 ++++++++++++++++++++
> >   drivers/platform/x86/lenovo-wmi-capdata01.h |  29 +++++
> >   5 files changed, 172 insertions(+)
> >   create mode 100644 drivers/platform/x86/lenovo-wmi-capdata01.c
> >   create mode 100644 drivers/platform/x86/lenovo-wmi-capdata01.h
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 6dde75922aaf..56ead241a053 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -13164,6 +13164,8 @@ L:    platform-driver-x86@...r.kernel.org
> >   S:  Maintained
> >   F:  Documentation/wmi/devices/lenovo-wmi-gamezone.rst
> >   F:  Documentation/wmi/devices/lenovo-wmi-other.rst
> > +F:   drivers/platform/x86/lenovo-wmi-capdata01.c
> > +F:   drivers/platform/x86/lenovo-wmi-capdata01.h
> >   F:  drivers/platform/x86/lenovo-wmi-events.c
> >   F:  drivers/platform/x86/lenovo-wmi-events.h
> >   F:  drivers/platform/x86/lenovo-wmi-helpers.c
> > diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
> > index 13b8f4ac5dc5..64663667f0cb 100644
> > --- a/drivers/platform/x86/Kconfig
> > +++ b/drivers/platform/x86/Kconfig
> > @@ -467,6 +467,10 @@ config LENOVO_WMI_HELPERS
> >       tristate
> >       depends on ACPI_WMI
> >
> > +config LENOVO_WMI_DATA01
> > +     tristate
> > +     depends on ACPI_WMI
> > +
> >   config IDEAPAD_LAPTOP
> >       tristate "Lenovo IdeaPad Laptop Extras"
> >       depends on ACPI
> > diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
> > index fc039839286a..7a35c77221b7 100644
> > --- a/drivers/platform/x86/Makefile
> > +++ b/drivers/platform/x86/Makefile
> > @@ -69,6 +69,7 @@ obj-$(CONFIG_THINKPAD_LMI)  += think-lmi.o
> >   obj-$(CONFIG_YOGABOOK)              += lenovo-yogabook.o
> >   obj-$(CONFIG_YT2_1380)              += lenovo-yoga-tab2-pro-1380-fastcharger.o
> >   obj-$(CONFIG_LENOVO_WMI_CAMERA)     += lenovo-wmi-camera.o
> > +obj-$(CONFIG_LENOVO_WMI_DATA01)      += lenovo-wmi-capdata01.o
> >   obj-$(CONFIG_LENOVO_WMI_EVENTS)     += lenovo-wmi-events.o
> >   obj-$(CONFIG_LENOVO_WMI_HELPERS)    += lenovo-wmi-helpers.o
> >
> > diff --git a/drivers/platform/x86/lenovo-wmi-capdata01.c b/drivers/platform/x86/lenovo-wmi-capdata01.c
> > new file mode 100644
> > index 000000000000..b6876611ffd9
> > --- /dev/null
> > +++ b/drivers/platform/x86/lenovo-wmi-capdata01.c
> > @@ -0,0 +1,136 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + * LENOVO_CAPABILITY_DATA_01 WMI data block driver. This interface provides
> > + * information on tunable attributes used by the "Other Mode" WMI interface,
> > + * including if it is supported by the hardware, the default_value, max_value,
> > + * min_value, and step increment.
> > + *
> > + * Copyright(C) 2025 Derek J. Clark <derekjohn.clark@...il.com>
> > + */
> > +
> > +#include <linux/cleanup.h>
> > +#include <linux/component.h>
> > +#include <linux/container_of.h>
> > +#include <linux/device.h>
> > +#include <linux/gfp_types.h>
> > +#include <linux/types.h>
> > +#include <linux/wmi.h>
> > +#include "lenovo-wmi-capdata01.h"
>
> Hi,
>
> please also include linux/acpi.h, linux/export.h and linux/module.h.
>
> > +
> > +/* Interface GUIDs */
> > +#define LENOVO_CAPABILITY_DATA_01_GUID "7A8F5407-CB67-4D6E-B547-39B3BE018154"
> > +
> > +struct lwmi_cd01_priv {
> > +     struct wmi_device *wdev;
> > +};
> > +
> > +/*
>
> /* -> /**
>
> > + * lenovo_cd01_component_bind() - On master bind, caches all capability data on
> > + * the master device.
> > + * @cd01_dev: Pointer to the capability data 01 parent device.
> > + * @om_dev: Pointer to the other mode parent device.
> > + * @data: capdata01_list object pointer to return the capability data with.
> > + *
> > + * Returns: 0, or an error.
> > + */
> > +static int lenovo_cd01_component_bind(struct device *cd01_dev,
> > +                                   struct device *om_dev, void *data)
> > +{
> > +     struct lwmi_cd01_priv *priv = dev_get_drvdata(cd01_dev);
> > +     int count, idx;
> > +
> > +     if (!priv)
> > +             return -ENODEV;
>
> This check is unnecessary, please drop.
>

Acked

> > +
> > +     count = wmidev_instance_count(priv->wdev);
> > +
> > +     if (count == 0)
> > +             return -EINVAL;
>
> The WMI driver core already ensures that WMI devices with 0 instances are
> rejected. Please drop this check.
>

Good to know, thanks.

> > +
> > +     ((struct cd01_list *)data)->count = count;
> > +     ((struct cd01_list *)data)->data = devm_kmalloc_array(om_dev, count,
> > +                                                           sizeof(struct capdata01 *),
> > +                                                           GFP_KERNEL);
>
> Two things:
>
>   - using a local variable with a type of struct cd01_list * results in cleaner source code here
>
>   - using devres is not possible inside the component callbacks, since the lifetime of the component
>     device is not necessarily tied to the lifetime of the underlying device.
>
> I suggest you move the whole WMI data querying into lwmi_cd01_probe(), because then you can keep using
> devres.
>

Doing this in probe() puts the list on lwmi_cd01_priv. Should I copy
that data on bind, or pass back a pointer to the cd01 device struct
and use an exported function on cd01 and dev_get_drvdata to access
priv->list->data[idx] when needed? I prefer the latter as this avoids
needing to do devm memory allocation in component/master binds, then I
can check for NULL when accessing and clear the pointer on
master_unbind to avoid calling to a removed device driver.

(snip)

> > +struct cd01_list {
> > +     struct capdata01 **data;
> > +     int count;
> > +};
>
> In order to save memory you could try something like this:
>
> struct cd01_list {
>         size_t count;
>         struct capdata01 data[];
> };
>
> This way you
>
> 1. Avoid the memory fragmentation resulting from multiple memory allocations.
>
> 2. Omit two pointers when accessing the data.
>
> You can use struct_size() from linux/overflow.h to calculate the size of such
> an array with a trailing flexible array.
>
> Thanks,
> Armin Wolf
>

I think I have this part working in my branch. Using devm_kzalloc also
allows me to omit manually setting NULL in a few cases, which is
cleaner. Is it preferred to use struct_size() directly in the
devm_kzalloc call, or create a separate `size` variable to set the
result to and pass that into the function?

- Derek


> > +
> > +int lwmi_cd01_match(struct device *dev, void *data);
> > +
> > +#endif /* !_LENOVO_WMI_CAPDATA01_H_ */

Powered by blists - more mailing lists