Merge tag 'staging-5.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging

Pull staging and IIO driver updates from Greg KH:
 "Here is the big staging/iio driver update for 5.4-rc1.

  Lots of churn here, with a few driver/filesystems moving out of
  staging finally:

     - erofs moved out of staging

     - greybus core code moved out of staging

  Along with that, a new filesytem has been added:

     - extfat

  to provide support for those devices requiring that filesystem (i.e.
  transfer devices to/from windows systems or printers)

  Other than that, there a number of new IIO drivers, and lots and lots
  and lots of staging driver cleanups and minor fixes as people continue
  to dig into those for easy changes.

  All of these have been in linux-next for a while with no reported
  issues"

* tag 'staging-5.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging: (453 commits)
  Staging: gasket: Use temporaries to reduce line length.
  Staging: octeon: Avoid several usecases of strcpy
  staging: vhciq_core: replace snprintf with scnprintf
  staging: wilc1000: avoid twice IRQ handler execution for each single interrupt
  staging: wilc1000: remove unused interrupt status handling code
  staging: fbtft: make several arrays static const, makes object smaller
  staging: rtl8188eu: make two arrays static const, makes object smaller
  staging: rtl8723bs: core: Remove Macro "IS_MAC_ADDRESS_BROADCAST"
  dt-bindings: anybus-controller: move to staging/ tree
  staging: emxx_udc: remove local TRUE/FALSE definition
  staging: wilc1000: look for rtc_clk clock
  staging: dt-bindings: wilc1000: add optional rtc_clk property
  staging: nvec: make use of devm_platform_ioremap_resource
  staging: exfat: drop unused function parameter
  Staging: exfat: Avoid use of strcpy
  staging: exfat: use integer constants
  staging: exfat: cleanup spacing for casts
  staging: exfat: cleanup spacing for operators
  staging: rtl8723bs: hal: remove redundant variable n
  staging: pi433: Fix typo in documentation
  ...

1 files changed, 210 insertions, 0 deletions

diff --git a/Documentation/filesystems/erofs.txt b/Documentation/filesystems/erofs.txt
new file mode 100644
index 000000000000..b0c085326e2e
--- /dev/null
+++ b/Documentation/filesystems/erofs.txt
@@ -0,0 +1,210 @@
+Overview
+========
+
+EROFS file-system stands for Enhanced Read-Only File System. Different
+from other read-only file systems, it aims to be designed for flexibility,
+scalability, but be kept simple and high performance.
+
+It is designed as a better filesystem solution for the following scenarios:
+ - read-only storage media or
+
+ - part of a fully trusted read-only solution, which means it needs to be
+   immutable and bit-for-bit identical to the official golden image for
+   their releases due to security and other considerations and
+
+ - hope to save some extra storage space with guaranteed end-to-end performance
+   by using reduced metadata and transparent file compression, especially
+   for those embedded devices with limited memory (ex, smartphone);
+
+Here is the main features of EROFS:
+ - Little endian on-disk design;
+
+ - Currently 4KB block size (nobh) and therefore maximum 16TB address space;
+
+ - Metadata & data could be mixed by design;
+
+ - 2 inode versions for different requirements:
+                          v1            v2
+   Inode metadata size:   32 bytes      64 bytes
+   Max file size:         4 GB          16 EB (also limited by max. vol size)
+   Max uids/gids:         65536         4294967296
+   File creation time:    no            yes (64 + 32-bit timestamp)
+   Max hardlinks:         65536         4294967296
+   Metadata reserved:     4 bytes       14 bytes
+
+ - Support extended attributes (xattrs) as an option;
+
+ - Support xattr inline and tail-end data inline for all files;
+
+ - Support POSIX.1e ACLs by using xattrs;
+
+ - Support transparent file compression as an option:
+   LZ4 algorithm with 4 KB fixed-output compression for high performance;
+
+The following git tree provides the file system user-space tools under
+development (ex, formatting tool mkfs.erofs):
+>> git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs-utils.git
+
+Bugs and patches are welcome, please kindly help us and send to the following
+linux-erofs mailing list:
+>> linux-erofs mailing list   <linux-erofs@lists.ozlabs.org>
+
+Mount options
+=============
+
+(no)user_xattr         Setup Extended User Attributes. Note: xattr is enabled
+                       by default if CONFIG_EROFS_FS_XATTR is selected.
+(no)acl                Setup POSIX Access Control List. Note: acl is enabled
+                       by default if CONFIG_EROFS_FS_POSIX_ACL is selected.
+cache_strategy=%s      Select a strategy for cached decompression from now on:
+                         disabled: In-place I/O decompression only;
+                        readahead: Cache the last incomplete compressed physical
+                                   cluster for further reading. It still does
+                                   in-place I/O decompression for the rest
+                                   compressed physical clusters;
+                       readaround: Cache the both ends of incomplete compressed
+                                   physical clusters for further reading.
+                                   It still does in-place I/O decompression
+                                   for the rest compressed physical clusters.
+
+On-disk details
+===============
+
+Summary
+-------
+Different from other read-only file systems, an EROFS volume is designed
+to be as simple as possible:
+
+                                |-> aligned with the block size
+   ____________________________________________________________
+  | |SB| | ... | Metadata | ... | Data | Metadata | ... | Data |
+  |_|__|_|_____|__________|_____|______|__________|_____|______|
+  0 +1K
+
+All data areas should be aligned with the block size, but metadata areas
+may not. All metadatas can be now observed in two different spaces (views):
+ 1. Inode metadata space
+    Each valid inode should be aligned with an inode slot, which is a fixed
+    value (32 bytes) and designed to be kept in line with v1 inode size.
+
+    Each inode can be directly found with the following formula:
+         inode offset = meta_blkaddr * block_size + 32 * nid
+
+                                |-> aligned with 8B
+                                           |-> followed closely
+    + meta_blkaddr blocks                                      |-> another slot
+     _____________________________________________________________________
+    |  ...   | inode |  xattrs  | extents  | data inline | ... | inode ...
+    |________|_______|(optional)|(optional)|__(optional)_|_____|__________
+             |-> aligned with the inode slot size
+                  .                   .
+                .                         .
+              .                              .
+            .                                    .
+          .                                         .
+        .                                              .
+      .____________________________________________________|-> aligned with 4B
+      | xattr_ibody_header | shared xattrs | inline xattrs |
+      |____________________|_______________|_______________|
+      |->    12 bytes    <-|->x * 4 bytes<-|               .
+                          .                .                 .
+                    .                      .                   .
+               .                           .                     .
+           ._______________________________.______________________.
+           | id | id | id | id |  ... | id | ent | ... | ent| ... |
+           |____|____|____|____|______|____|_____|_____|____|_____|
+                                           |-> aligned with 4B
+                                                       |-> aligned with 4B
+
+    Inode could be 32 or 64 bytes, which can be distinguished from a common
+    field which all inode versions have -- i_advise:
+
+        __________________               __________________
+       |     i_advise     |             |     i_advise     |
+       |__________________|             |__________________|
+       |        ...       |             |        ...       |
+       |                  |             |                  |
+       |__________________| 32 bytes    |                  |
+                                        |                  |
+                                        |__________________| 64 bytes
+
+    Xattrs, extents, data inline are followed by the corresponding inode with
+    proper alignes, and they could be optional for different data mappings,
+    _currently_ there are totally 3 valid data mappings supported:
+
+     1) flat file data without data inline (no extent);
+     2) fixed-output size data compression (must have extents);
+     3) flat file data with tail-end data inline (no extent);
+
+    The size of the optional xattrs is indicated by i_xattr_count in inode
+    header. Large xattrs or xattrs shared by many different files can be
+    stored in shared xattrs metadata rather than inlined right after inode.
+
+ 2. Shared xattrs metadata space
+    Shared xattrs space is similar to the above inode space, started with
+    a specific block indicated by xattr_blkaddr, organized one by one with
+    proper align.
+
+    Each share xattr can also be directly found by the following formula:
+         xattr offset = xattr_blkaddr * block_size + 4 * xattr_id
+
+                           |-> aligned by  4 bytes
+    + xattr_blkaddr blocks                     |-> aligned with 4 bytes
+     _________________________________________________________________________
+    |  ...   | xattr_entry |  xattr data | ... |  xattr_entry | xattr data  ...
+    |________|_____________|_____________|_____|______________|_______________
+
+Directories
+-----------
+All directories are now organized in a compact on-disk format. Note that
+each directory block is divided into index and name areas in order to support
+random file lookup, and all directory entries are _strictly_ recorded in
+alphabetical order in order to support improved prefix binary search
+algorithm (could refer to the related source code).
+
+                 ___________________________
+                /                           |
+               /              ______________|________________
+              /              /              | nameoff1       | nameoffN-1
+ ____________.______________._______________v________________v__________
+| dirent | dirent | ... | dirent | filename | filename | ... | filename |
+|___.0___|____1___|_____|___N-1__|____0_____|____1_____|_____|___N-1____|
+     \                           ^
+      \                          |                           * could have
+       \                         |                             trailing '\0'
+        \________________________| nameoff0
+
+                             Directory block
+
+Note that apart from the offset of the first filename, nameoff0 also indicates
+the total number of directory entries in this block since it is no need to
+introduce another on-disk field at all.
+
+Compression
+-----------
+Currently, EROFS supports 4KB fixed-output clustersize transparent file
+compression, as illustrated below:
+
+         |---- Variant-Length Extent ----|-------- VLE --------|----- VLE -----
+         clusterofs                      clusterofs            clusterofs
+         |                               |                     |   logical data
+_________v_______________________________v_____________________v_______________
+... |    .        |             |        .    |             |  .          | ...
+____|____.________|_____________|________.____|_____________|__.__________|____
+    |-> cluster <-|-> cluster <-|-> cluster <-|-> cluster <-|-> cluster <-|
+         size          size          size          size          size
+          .                             .                .                   .
+           .                       .               .                  .
+            .                  .              .                .
+      _______._____________._____________._____________._____________________
+         ... |             |             |             | ... physical data
+      _______|_____________|_____________|_____________|_____________________
+             |-> cluster <-|-> cluster <-|-> cluster <-|
+                  size          size          size
+
+Currently each on-disk physical cluster can contain 4KB (un)compressed data
+at most. For each logical cluster, there is a corresponding on-disk index to
+describe its cluster type, physical cluster address, etc.
+
+See "struct z_erofs_vle_decompressed_index" in erofs_fs.h for more details.
+