From e09b41010ba33a20a87472ee821fa407a5b8da36 Mon Sep 17 00:00:00 2001 From: José Pekkarinen Date: Mon, 11 Apr 2016 10:41:07 +0300 Subject: These changes are the raw update to linux-4.4.6-rt14. Kernel sources are taken from kernel.org, and rt patch from the rt wiki download page. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit During the rebasing, the following patch collided: Force tick interrupt and get rid of softirq magic(I70131fb85). Collisions have been removed because its logic was found on the source already. Change-Id: I7f57a4081d9deaa0d9ccfc41a6c8daccdee3b769 Signed-off-by: José Pekkarinen --- kernel/Documentation/i2c/slave-interface | 34 ++++++++++++++++++++------------ 1 file changed, 21 insertions(+), 13 deletions(-) (limited to 'kernel/Documentation/i2c/slave-interface') diff --git a/kernel/Documentation/i2c/slave-interface b/kernel/Documentation/i2c/slave-interface index b228ca54b..61ed05cd9 100644 --- a/kernel/Documentation/i2c/slave-interface +++ b/kernel/Documentation/i2c/slave-interface @@ -3,16 +3,16 @@ Linux I2C slave interface description by Wolfram Sang in 2014-15 -Linux can also be an I2C slave in case I2C controllers have slave support. -Besides this HW requirement, one also needs a software backend providing the -actual functionality. An example for this is the slave-eeprom driver, which -acts as a dual memory driver. While another I2C master on the bus can access it -like a regular EEPROM, the Linux I2C slave can access the content via sysfs and -retrieve/provide information as needed. The software backend driver and the I2C -bus driver communicate via events. Here is a small graph visualizing the data -flow and the means by which data is transported. The dotted line marks only one -example. The backend could also use e.g. a character device, be in-kernel -only, or something completely different: +Linux can also be an I2C slave if the I2C controller in use has slave +functionality. For that to work, one needs slave support in the bus driver plus +a hardware independent software backend providing the actual functionality. An +example for the latter is the slave-eeprom driver, which acts as a dual memory +driver. While another I2C master on the bus can access it like a regular +EEPROM, the Linux I2C slave can access the content via sysfs and handle data as +needed. The backend driver and the I2C bus driver communicate via events. Here +is a small graph visualizing the data flow and the means by which data is +transported. The dotted line marks only one example. The backend could also +use a character device, be in-kernel only, or something completely different: e.g. sysfs I2C slave events I/O registers @@ -31,10 +31,13 @@ User manual =========== I2C slave backends behave like standard I2C clients. So, you can instantiate -them as described in the document 'instantiating-devices'. A quick example for -instantiating the slave-eeprom driver from userspace at address 0x64 on bus 1: +them as described in the document 'instantiating-devices'. The only difference +is that i2c slave backends have their own address space. So, you have to add +0x1000 to the address you would originally request. An example for +instantiating the slave-eeprom driver from userspace at the 7 bit address 0x64 +on bus 1: - # echo slave-24c02 0x64 > /sys/bus/i2c/devices/i2c-1/new_device + # echo slave-24c02 0x1064 > /sys/bus/i2c/devices/i2c-1/new_device Each backend should come with separate documentation to describe its specific behaviour and setup. @@ -43,6 +46,11 @@ behaviour and setup. Developer manual ================ +First, the events which are used by the bus driver and the backend will be +described in detail. After that, some implementation hints for extending bus +drivers and writing backends will be given. + + I2C slave events ---------------- -- cgit 1.2.3-korg