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Commit cfa0327b authored by Wolfram Sang's avatar Wolfram Sang Committed by Wolfram Sang
Browse files

i2c: support 10 bit and slave addresses in sysfs 'new_device' 



We now have seperate address spaces for 10 bit and we-are-slave clients.
Update the sysfs device instantiation method to support these types by
accepting the address offsets that are assigned to the extra address
spaces. Update the documentation, too.

Signed-off-by: default avatarWolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
parent 9bccc70a

Documentation/i2c/slave-interface

+6 −3
Original line number Diff line number Diff line
@@ -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.

Documentation/i2c/ten-bit-addresses

+4 −0
Original line number Diff line number Diff line
@@ -2,6 +2,10 @@ The I2C protocol knows about two kinds of device addresses: normal 7 bit 
addresses, and an extended set of 10 bit addresses. The sets of addresses

do not intersect: the 7 bit address 0x10 is not the same as the 10 bit

address 0x10 (though a single device could respond to both of them).

To avoid ambiguity, the user sees 10 bit addresses mapped to a different

address space, namely 0xa000-0xa3ff. The leading 0xa (= 10) represents the

10 bit mode. This is used for creating device names in sysfs. It is also

needed when instantiating 10 bit devices via the new_device file in sysfs.



I2C messages to and from 10-bit address devices have a different format.

See the I2C specification for the details.

drivers/i2c/i2c-core.c

+11 −1
Original line number Diff line number Diff line
@@ -1158,6 +1158,16 @@ i2c_sysfs_new_device(struct device *dev, struct device_attribute *attr, 
		return -EINVAL;

	}



	if ((info.addr & I2C_ADDR_OFFSET_TEN_BIT) == I2C_ADDR_OFFSET_TEN_BIT) {

		info.addr &= ~I2C_ADDR_OFFSET_TEN_BIT;

		info.flags |= I2C_CLIENT_TEN;

	}



	if (info.addr & I2C_ADDR_OFFSET_SLAVE) {

		info.addr &= ~I2C_ADDR_OFFSET_SLAVE;

		info.flags |= I2C_CLIENT_SLAVE;

	}



	client = i2c_new_device(adap, &info);

	if (!client)

		return -EINVAL;
@@ -1209,7 +1219,7 @@ i2c_sysfs_delete_device(struct device *dev, struct device_attribute *attr, 
			  i2c_adapter_depth(adap));

	list_for_each_entry_safe(client, next, &adap->userspace_clients,

				 detected) {

		if (client->addr == addr) {

		if (i2c_encode_flags_to_addr(client) == addr) {

			dev_info(dev, "%s: Deleting device %s at 0x%02hx\n",

				 "delete_device", client->name, client->addr);