driver-api: create an edac.rst file with EDAC documentation

Currently, there's no device driver documentation for the EDAC
subsystem at the driver-api book. Fill in the blanks for the
structures and functions that misses documentation, uniform
the word on the existing ones, and add a new edac.rst file at
driver-api, in order to document the EDAC subsystem.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

1 files changed, 72 insertions, 0 deletions

diff --git a/Documentation/driver-api/edac.rst b/Documentation/driver-api/edac.rst
new file mode 100644
index 000000000000..3771e768fda1
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+++ b/Documentation/driver-api/edac.rst
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+Error Detection And Correction (EDAC) Devices
+=============================================
+
+Memory Controllers
+------------------
+
+Most of the EDAC core is focused on doing Memory Controller error detection.
+The :c:func:`edac_mc_alloc`. It uses internally the struct ``mem_ctl_info``
+to describe the memory controllers, with is an opaque struct for the EDAC
+drivers. Only the EDAC core is allowed to touch it.
+
+.. kernel-doc:: include/linux/edac.h
+
+.. kernel-doc:: drivers/edac/edac_mc.h
+
+PCI Controllers
+---------------
+
+The EDAC subsystem provides a mechanism to handle PCI controllers by calling
+the :c:func:`edac_pci_alloc_ctl_info`. It will use the struct
+:c:type:`edac_pci_ctl_info` to describe the PCI controllers.
+
+.. kernel-doc:: drivers/edac/edac_pci.h
+
+EDAC Blocks
+-----------
+
+The EDAC subsystem also provides a generic mechanism to report errors on
+other parts of the hardware via :c:func:`edac_device_alloc_ctl_info` function.
+
+The structures :c:type:`edac_dev_sysfs_block_attribute`,
+:c:type:`edac_device_block`, :c:type:`edac_device_instance` and
+:c:type:`edac_device_ctl_info` provide a generic or abstract 'edac_device'
+representation at sysfs.
+
+This set of structures and the code that implements the APIs for the same, provide for registering EDAC type devices which are NOT standard memory or
+PCI, like:
+
+- CPU caches (L1 and L2)
+- DMA engines
+- Core CPU switches
+- Fabric switch units
+- PCIe interface controllers
+- other EDAC/ECC type devices that can be monitored for
+  errors, etc.
+
+It allows for a 2 level set of hierarchy.
+
+For example, a cache could be composed of L1, L2 and L3 levels of cache.
+Each CPU core would have its own L1 cache, while sharing L2 and maybe L3
+caches. On such case, those can be represented via the following sysfs
+nodes::
+
+        /sys/devices/system/edac/..
+
+        pci/            <existing pci directory (if available)>
+        mc/             <existing memory device directory>
+        cpu/cpu0/..     <L1 and L2 block directory>
+                /L1-cache/ce_count
+                         /ue_count
+                /L2-cache/ce_count
+                         /ue_count
+        cpu/cpu1/..     <L1 and L2 block directory>
+                /L1-cache/ce_count
+                         /ue_count
+                /L2-cache/ce_count
+                         /ue_count
+        ...
+
+        the L1 and L2 directories would be "edac_device_block's"
+
+.. kernel-doc:: drivers/edac/edac_device.h