Re: [PATCH 4/5] ACPI / property: Allow holes in reference properties

Mika Westerberg
2016-09-29T06:57:28Z

On Wed, Sep 28, 2016 at 11:36:10PM +0200, Rafael J. Wysocki wrote:
> On Fri, Sep 23, 2016 at 4:57 PM, Mika Westerberg
> <mika.westerberg@linux.intel.com> wrote:
> > DT allows holes or empty phandles for references. This is used for example
> > in SPI subsystem where some chip selects are native and others are regular
> > GPIOs. In ACPI _DSD we currently do not support this but instead the
> > preceding reference "consumes" all following integer arguments.
> >
> > For example we would like to support something like the below ASL fragment
> > for SPI:
> >
> > Package () {
> > "cs-gpios",
> > Package () {
> > ^GPIO, 19, 0, 0, // GPIO CS0
> > 0, // Native CS
> > ^GPIO, 20, 0, 0, // GPIO CS1
> > }
> > }
> >
> > The zero in the middle means "no entry" or NULL reference. To support this
> > we add a new function acpi_node_get_property_reference_fixed_args() that
> > takes number of expected arguments as parameter. Function returns -ENOENT
> > if the corresponding index resolves to the "no entry" reference.
> >
> > Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
> > ---
> > drivers/acpi/property.c | 116 +++++++++++++++++++++++++++++++++++-------------
> > include/linux/acpi.h | 3 ++
> > 2 files changed, 89 insertions(+), 30 deletions(-)
> >
> > diff --git a/drivers/acpi/property.c b/drivers/acpi/property.c
> > index f2fd3fee588a..b255c4442a05 100644
> > --- a/drivers/acpi/property.c
> > +++ b/drivers/acpi/property.c
> > @@ -472,6 +472,7 @@ static int acpi_data_get_property_array(struct acpi_device_data *data,
> > * @data: ACPI device data object containing the property
> > * @propname: Name of the property
> > * @index: Index of the reference to return
> > + * @num_args: Maximum number of arguments after each reference
> > * @args: Location to store the returned reference with optional arguments
> > *
> > * Find property with @name, verifify that it is a package containing at least
> > @@ -485,8 +486,8 @@ static int acpi_data_get_property_array(struct acpi_device_data *data,
> > * Return: %0 on success, negative error code on failure.
> > */
> > static int acpi_data_get_property_reference(struct acpi_device_data *data,
> > - const char *propname, size_t index,
> > - struct acpi_reference_args *args)
> > + const char *propname, size_t index, size_t num_args,
> > + struct acpi_reference_args *args)
> > {
> > const union acpi_object *element, *end;
> > const union acpi_object *obj;
> > @@ -532,41 +533,52 @@ static int acpi_data_get_property_reference(struct acpi_device_data *data,
> > while (element < end) {
> > u32 nargs, i;
> >
> > - if (element->type != ACPI_TYPE_LOCAL_REFERENCE)
> > - return -EPROTO;
> > -
> > - ret = acpi_bus_get_device(element->reference.handle, &device);
> > - if (ret)
> > - return -ENODEV;
> > -
> > - element++;
> > - nargs = 0;
> > -
> > - /* assume following integer elements are all args */
> > - for (i = 0; element + i < end; i++) {
> > - int type = element[i].type;
> > + if (element->type == ACPI_TYPE_LOCAL_REFERENCE) {
> > + ret = acpi_bus_get_device(element->reference.handle,
> > + &device);
> > + if (ret)
> > + return -ENODEV;
> > +
> > + nargs = 0;
> > + element++;
> > +
> > + /* assume following integer elements are all args */
> > + for (i = 0; element + i < end && i < num_args; i++) {
> > + int type = element[i].type;
> > +
> > + if (type == ACPI_TYPE_INTEGER)
> > + nargs++;
> > + else if (type == ACPI_TYPE_LOCAL_REFERENCE)
> > + break;
> > + else
> > + return -EPROTO;
> > + }
> >
> > - if (type == ACPI_TYPE_INTEGER)
> > - nargs++;
> > - else if (type == ACPI_TYPE_LOCAL_REFERENCE)
> > - break;
> > - else
> > + if (nargs > MAX_ACPI_REFERENCE_ARGS)
> > return -EPROTO;
> > - }
> >
> > - if (idx++ == index) {
> > - args->adev = device;
> > - args->nargs = nargs;
> > - for (i = 0; i < nargs; i++)
> > - args->args[i] = element[i].integer.value;
> > + if (idx == index) {
> > + args->adev = device;
> > + args->nargs = nargs;
> > + for (i = 0; i < nargs; i++)
> > + args->args[i] = element[i].integer.value;
> >
> > - return 0;
> > + return 0;
> > + }
> > +
> > + element += nargs;
> > + } else if (element->type == ACPI_TYPE_INTEGER) {
> > + if (idx == index)
> > + return -ENOENT;
> > + element++;
> > + } else {
> > + return -EPROTO;
> > }
> >
> > - element += nargs;
> > + idx++;
> > }
> >
> > - return -EPROTO;
> > + return -ENODATA;
> > }
> >
> > /**
> > @@ -582,10 +594,54 @@ int acpi_node_get_property_reference(struct fwnode_handle *fwnode,
> > {
> > struct acpi_device_data *data = acpi_device_data_of_node(fwnode);
> >
> > - return data ? acpi_data_get_property_reference(data, name, index, args) : -EINVAL;
> > + if (!data)
> > + return -EINVAL;
> > +
> > + return acpi_data_get_property_reference(data, name, index,
> > + MAX_ACPI_REFERENCE_ARGS, args);
> > }
> > EXPORT_SYMBOL_GPL(acpi_node_get_property_reference);
>
> gpiolib-acpi is the only user of this AFAICS, so why don't we change
> the definition of acpi_node_get_property_reference() to take one extra
> argument and update the caller to pass MAX_ACPI_REFERENCE_ARGS?

Unfortunately there are these (which I think should not call that
function directly anyway):

drivers/net/ethernet/apm/xgene/xgene_enet_hw.c: status = acpi_node_get_property_reference(fw_node, "phy-handle", 0,
drivers/net/ethernet/hisilicon/hns/hns_dsaf_mac.c: rc = acpi_node_get_property_reference(
drivers/net/ethernet/hisilicon/hns/hns_enet.c: ret = acpi_node_get_property_reference(dev->fwnode,

So we would need to update those as well. Not a big deal, though.