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The logical address of every GPE block in system memory must be known before passing it to acpi_ev_initialize_gpe_block(), because memory cannot be mapped on the fly from an interrupt handler. Accordingly, the host OS must map every GPE block in system memory upfront and it can store the logical addresses of GPE blocks for future use. If these logical addresses were known to ACPICA, it could use them instead of the corresponding physical addresses of GPE block for GPE register accesses and the memory mapping lookups carried out by acpi_os_read_memory() and acpi_os_write_memory() on every attempt to access a GPE register would not be necessary any more. To allow that to happen, introduce the ACPI_GPE_USE_LOGICAL_ADDRESSES symbol to indicate whether or not the host OS wants ACPICA to use the logical addresses of GPE registers in system memory directly (which is the case if this symbol is defined). Moreover, conditional on whether ACPI_GPE_USE_LOGICAL_ADDRESSES is defined, introduce two new global variables for storing the logical addresses of the FADT GPE blocks 0 and 1, respectively, acpi_gbl_xgpe0_block_logical_address and acpi_gbl_xgpe1_block_logical_address, make acpi_ev_gpe_initialize() pass their values instead of the physical addresses of the GPE blocks in question to acpi_ev_create_gpe_block() and modify acpi_hw_gpe_read() and acpi_hw_gpe_write() to access memory directly via the addresses stored in the struct acpi_gpe_address objects, which are expected to be the logical addresses of GPE registers if ACPI_GPE_USE_LOGICAL_ADDRESSES is defined. With the above changes in place, a host OS wanting ACPICA to access GPE registers directly through their logical addresses needs to define the ACPI_GPE_USE_LOGICAL_ADDRESSES symbol and make sure that the logical addresses of the FADT GPE blocks 0 and 1 are stored in acpi_gbl_xgpe0_block_logical_address and acpi_gbl_xgpe1_block_logical_address, respectively, prior to calling acpi_ev_gpe_initialize(). [If such a host OS also uses acpi_install_gpe_block() to add non-FADT GPE register blocks located in system memory, it must pass their logical addresses instead of their physical addresses to this function.] Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.