diff options
Diffstat (limited to '')
| -rw-r--r-- | Documentation/firmware-guide/acpi/enumeration.rst | 16 | ||||
| -rw-r--r-- | Documentation/firmware-guide/acpi/osi.rst | 25 |
2 files changed, 19 insertions, 22 deletions
diff --git a/Documentation/firmware-guide/acpi/enumeration.rst b/Documentation/firmware-guide/acpi/enumeration.rst index dbb03022b127..b9dc0c603f36 100644 --- a/Documentation/firmware-guide/acpi/enumeration.rst +++ b/Documentation/firmware-guide/acpi/enumeration.rst @@ -21,7 +21,7 @@ possible we decided to do following: - Devices behind real busses where there is a connector resource are represented as struct spi_device or struct i2c_device. Note that standard UARTs are not busses so there is no struct uart_device, - although some of them may be represented by sturct serdev_device. + although some of them may be represented by struct serdev_device. As both ACPI and Device Tree represent a tree of devices (and their resources) this implementation follows the Device Tree way as much as @@ -205,7 +205,7 @@ Here is what the ACPI namespace for a SPI slave might look like:: } ... -The SPI device drivers only need to add ACPI IDs in a similar way than with +The SPI device drivers only need to add ACPI IDs in a similar way to the platform device drivers. Below is an example where we add ACPI support to at25 SPI eeprom driver (this is meant for the above ACPI snippet):: @@ -362,7 +362,7 @@ These GPIO numbers are controller relative and path "\\_SB.PCI0.GPI0" specifies the path to the controller. In order to use these GPIOs in Linux we need to translate them to the corresponding Linux GPIO descriptors. -There is a standard GPIO API for that and is documented in +There is a standard GPIO API for that and it is documented in Documentation/admin-guide/gpio/. In the above example we can get the corresponding two GPIO descriptors with @@ -538,8 +538,8 @@ information. PCI hierarchy representation ============================ -Sometimes could be useful to enumerate a PCI device, knowing its position on the -PCI bus. +Sometimes it could be useful to enumerate a PCI device, knowing its position on +the PCI bus. For example, some systems use PCI devices soldered directly on the mother board, in a fixed position (ethernet, Wi-Fi, serial ports, etc.). In this conditions it @@ -550,7 +550,7 @@ To identify a PCI device, a complete hierarchical description is required, from the chipset root port to the final device, through all the intermediate bridges/switches of the board. -For example, let us assume to have a system with a PCIe serial port, an +For example, let's assume we have a system with a PCIe serial port, an Exar XR17V3521, soldered on the main board. This UART chip also includes 16 GPIOs and we want to add the property ``gpio-line-names`` [1] to these pins. In this case, the ``lspci`` output for this component is:: @@ -593,8 +593,8 @@ of the chipset bridge (also called "root port") with address:: Bus: 0 - Device: 14 - Function: 1 -To find this information is necessary disassemble the BIOS ACPI tables, in -particular the DSDT (see also [2]):: +To find this information, it is necessary to disassemble the BIOS ACPI tables, +in particular the DSDT (see also [2]):: mkdir ~/tables/ cd ~/tables/ diff --git a/Documentation/firmware-guide/acpi/osi.rst b/Documentation/firmware-guide/acpi/osi.rst index 05869c0045d7..784850adfcb6 100644 --- a/Documentation/firmware-guide/acpi/osi.rst +++ b/Documentation/firmware-guide/acpi/osi.rst @@ -41,26 +41,23 @@ But it is likely that they will all eventually be added. What should an OEM do if they want to support Linux and Windows using the same BIOS image? Often they need to do something different for Linux to deal with how Linux is different from Windows. -Here the BIOS should ask exactly what it wants to know: +In this case, the OEM should create custom ASL to be executed by the +Linux kernel and changes to Linux kernel drivers to execute this custom +ASL. The easiest way to accomplish this is to introduce a device specific +method (_DSM) that is called from the Linux kernel. + +In the past the kernel used to support something like: _OSI("Linux-OEM-my_interface_name") where 'OEM' is needed if this is an OEM-specific hook, and 'my_interface_name' describes the hook, which could be a quirk, a bug, or a bug-fix. -In addition, the OEM should send a patch to upstream Linux -via the linux-acpi@vger.kernel.org mailing list. When that patch -is checked into Linux, the OS will answer "YES" when the BIOS -on the OEM's system uses _OSI to ask if the interface is supported -by the OS. Linux distributors can back-port that patch for Linux -pre-installs, and it will be included by all distributions that -re-base to upstream. If the distribution can not update the kernel binary, -they can also add an acpi_osi=Linux-OEM-my_interface_name -cmdline parameter to the boot loader, as needed. - -If the string refers to a feature where the upstream kernel -eventually grows support, a patch should be sent to remove -the string when that support is added to the kernel. +However this was discovered to be abused by other BIOS vendors to change +completely unrelated code on completely unrelated systems. This prompted +an evaluation of all of it's uses. This uncovered that they aren't needed +for any of the original reasons. As such, the kernel will not respond to +any custom Linux-* strings by default. That was easy. Read on, to find out how to do it wrong. |