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authorIngo Molnar <mingo@kernel.org>2014-08-22 10:04:15 +0200
committerIngo Molnar <mingo@kernel.org>2014-08-22 10:04:15 +0200
commit80b304fd00e8b667775ff791121b61ecd7cd0c03 (patch)
treeb4f2ec59fe062c43343ee4c2f10a6bcd0e4dcd1b /Documentation/i2c/i2c-stub
parentfb21b84e7f809ef04b1e5aed5d463cf0d4866638 (diff)
parent6a7519e81321343165f89abb8b616df186d3e57a (diff)
Merge tag 'efi-urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/mfleming/efi into x86/urgent
Pull EFI fixes from Matt Fleming: * WARN_ON(!spin_is_locked()) always triggers on non-SMP machines. Swap it for the more canonical lockdep_assert_held() which always does the right thing - Guenter Roeck * Assign the correct value to efi.runtime_version on arm64 so that all the runtime services can be invoked - Semen Protsenko Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'Documentation/i2c/i2c-stub')
-rw-r--r--Documentation/i2c/i2c-stub23
1 files changed, 17 insertions, 6 deletions
diff --git a/Documentation/i2c/i2c-stub b/Documentation/i2c/i2c-stub
index fa4b669c166b..a16924fbd289 100644
--- a/Documentation/i2c/i2c-stub
+++ b/Documentation/i2c/i2c-stub
@@ -2,9 +2,9 @@ MODULE: i2c-stub
DESCRIPTION:
-This module is a very simple fake I2C/SMBus driver. It implements five
+This module is a very simple fake I2C/SMBus driver. It implements six
types of SMBus commands: write quick, (r/w) byte, (r/w) byte data, (r/w)
-word data, and (r/w) I2C block data.
+word data, (r/w) I2C block data, and (r/w) SMBus block data.
You need to provide chip addresses as a module parameter when loading this
driver, which will then only react to SMBus commands to these addresses.
@@ -19,6 +19,14 @@ A pointer register with auto-increment is implemented for all byte
operations. This allows for continuous byte reads like those supported by
EEPROMs, among others.
+SMBus block command support is disabled by default, and must be enabled
+explicitly by setting the respective bits (0x03000000) in the functionality
+module parameter.
+
+SMBus block commands must be written to configure an SMBus command for
+SMBus block operations. Writes can be partial. Block read commands always
+return the number of bytes selected with the largest write so far.
+
The typical use-case is like this:
1. load this module
2. use i2cset (from the i2c-tools project) to pre-load some data
@@ -39,15 +47,18 @@ unsigned long functionality:
value 0x1f0000 would only enable the quick, byte and byte data
commands.
+u8 bank_reg[10]
+u8 bank_mask[10]
+u8 bank_start[10]
+u8 bank_end[10]:
+ Optional bank settings. They tell which bits in which register
+ select the active bank, as well as the range of banked registers.
+
CAVEATS:
If your target driver polls some byte or word waiting for it to change, the
stub could lock it up. Use i2cset to unlock it.
-If the hardware for your driver has banked registers (e.g. Winbond sensors
-chips) this module will not work well - although it could be extended to
-support that pretty easily.
-
If you spam it hard enough, printk can be lossy. This module really wants
something like relayfs.