On Thu, Aug 28, 2014 at 12:29:00PM +0100, Lee Jones wrote:
> On Sun, 17 Aug 2014, Mika Westerberg wrote:
>
> > If an MFD device is backed by ACPI namespace, we should allow subdevice
> > drivers to access their corresponding ACPI companion devices through normal
> > means (e.g using ACPI_COMPANION()).
> >
> > This patch adds such support to the MFD core. If the MFD parent device
> > doesn't specify any ACPI _HID/_CID for the child device, the child device
> > will share the parent ACPI companion device. Otherwise the child device
> > will be assigned with the corresponding ACPI companion, if found in the
> > namespace below the parent.
> >
> > Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> > Reviewed-by: Darren Hart <dvhart@xxxxxxxxxxxxxxx>
> > ---
> > Documentation/acpi/enumeration.txt | 27 +++++++++++++++++++++++++
> > drivers/mfd/mfd-core.c | 41 ++++++++++++++++++++++++++++++++++++++
> > include/linux/mfd/core.h | 3 +++
> > 3 files changed, 71 insertions(+)
> >
> > diff --git a/Documentation/acpi/enumeration.txt b/Documentation/acpi/enumeration.txt
> > index e182be5e3c83..74e35c54febf 100644
> > --- a/Documentation/acpi/enumeration.txt
> > +++ b/Documentation/acpi/enumeration.txt
> > @@ -312,3 +312,30 @@ a code like this:
> >
> > There are also devm_* versions of these functions which release the
> > descriptors once the device is released.
> > +
> > +MFD devices
> > +~~~~~~~~~~~
> > +The MFD devices create platform devices from their children. For the
> > +child devices there needs to be an ACPI handle that they can use to
> > +reference parts of the ACPI namespace that relate to them. In the Linux
> > +MFD subsystem we provide two ways:
> > +
> > + o The children share the parent ACPI handle.
> > + o The MFD cell can specify the ACPI id of the device.
> > +
> > +For the first case, the MFD drivers do not need to do anything. The
> > +resulting child platform device will have its ACPI_COMPANION() set to point
> > +to the parent device.
> > +
> > +If the ACPI namespace has a device that we can match using an ACPI id,
> > +the id should be set like:
> > +
> > + static struct mfd_cell my_subdevice_cell = {
> > + .name = "my_subdevice",
> > + /* set the resources relative to the parent */
> > + .acpi_pnpid = "XYZ0001",
> > + };
> > +
> > +The ACPI id "XYZ0001" is then used to lookup an ACPI device directly under
> > +the MFD device and if found, that ACPI companion device is bound to the
> > +resulting child platform device.
> > diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c
> > index 892d343193ad..bb466b28b3b6 100644
> > --- a/drivers/mfd/mfd-core.c
> > +++ b/drivers/mfd/mfd-core.c
> > @@ -78,6 +78,45 @@ static int mfd_platform_add_cell(struct platform_device *pdev,
> > return 0;
> > }
> >
> > +#if IS_ENABLED(CONFIG_ACPI)
> > +static void mfd_acpi_add_device(const struct mfd_cell *cell,
> > + struct platform_device *pdev)
> > +{
> > + struct acpi_device *parent_adev;
> > + struct acpi_device *adev = NULL;
> > +
> > + parent_adev = ACPI_COMPANION(pdev->dev.parent);
> > + if (!parent_adev)
> > + return;
> > +
> > + /*
> > + * MFD child device gets its ACPI handle either from the ACPI
> > + * device directly under the parent that matches the acpi_pnpid or
> > + * it will use the parent handle if is no acpi_pnpid is given.
> > + */
> > + if (cell->acpi_pnpid) {
> > + struct acpi_device_id ids[2] = {};
> > + struct acpi_device *child_adev;
> > +
> > + strlcpy(ids[0].id, cell->acpi_pnpid, sizeof(ids[0].id));
> > + list_for_each_entry(child_adev, &parent_adev->children, node)
> > + if (acpi_match_device_ids(child_adev, ids)) {
> > + adev = child_adev;
> > + break;
> > + }
>
> What happens if cell->acpi_pnpid is provided, but not matched?
>
> Surely adev will them be NULL?
>
> In these cases shouldn't you then "adev = parent_adev"?
Good point. I'll fix that in the next version.
>
> > + } else {
> > + adev = parent_adev;
> > + }
> > +
> > + ACPI_COMPANION_SET(&pdev->dev, adev);
> > +}
> > +#else
> > +static inline void mfd_acpi_add_device(const struct mfd_cell *cell,
> > + struct platform_device *pdev)
> > +{
> > +}
> > +#endif
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