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ACPI: docs: enumeration: Discourage to use custom _DSM methods

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Since we have _DSD established and specified (ACPI v5.1+) there is no
need to use custom _DSM methods. Rewrite documentation to use _DSD.

Fixes: f60e707490 ("misc: at25: Make use of device property API")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Andy Shevchenko 2022-03-01 00:39:30 +02:00 committed by Rafael J. Wysocki
parent 7e57714cd0
commit b625fe6946
1 changed files with 21 additions and 27 deletions
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48
Documentation/firmware-guide/acpi/enumeration.rst
View file

@ -188,43 +188,37 @@ to at25 SPI eeprom driver (this is meant for the above ACPI snippet)::
};
Note that this driver actually needs more information like page size of the
eeprom etc. but at the time writing this there is no standard way of
passing those. One idea is to return this in _DSM method like::
eeprom, etc. This information can be passed via _DSD method like::
Device (EEP0)
{
...
Method (_DSM, 4, NotSerialized)
Name (_DSD, Package ()
{
Store (Package (6)
ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
Package ()
{
"byte-len", 1024,
"addr-mode", 2,
"page-size, 32
}, Local0)
Package () { "size", 1024 },
Package () { "pagesize", 32 },
Package () { "address-width", 16 },
}
})
}
// Check UUIDs etc.
Then the at25 SPI driver can get this configuration by calling device property
APIs during ->probe() phase like::
Return (Local0)
}
err = device_property_read_u32(dev, "size", &size);
if (err)
...error handling...
Then the at25 SPI driver can get this configuration by calling _DSM on its
ACPI handle like::
err = device_property_read_u32(dev, "pagesize", &page_size);
if (err)
...error handling...
struct acpi_buffer output = { ACPI_ALLOCATE_BUFFER, NULL };
struct acpi_object_list input;
acpi_status status;
/* Fill in the input buffer */
status = acpi_evaluate_object(ACPI_HANDLE(&spi->dev), "_DSM",
&input, &output);
if (ACPI_FAILURE(status))
/* Handle the error */
/* Extract the data here */
kfree(output.pointer);
err = device_property_read_u32(dev, "address-width", &addr_width);
if (err)
...error handling...
I2C serial bus support
======================