i2c read block

[Francis]

Hi,

I am trying to create an application on top/based on the i2c tools.

Everything was working well, except the i2c_smbus_block_process_call(), which returns an error when called.

Below is the output of i2cdetect -F:

Functionalities implemented by /dev/i2c-2:

I2C                              yes

SMBus Quick Command              no

SMBus Send Byte                  yes

SMBus Receive Byte               yes

SMBus Write Byte                 yes

SMBus Read Byte                  yes

SMBus Write Word                 yes

SMBus Read Word                  yes

SMBus Process Call               yes

SMBus Block Write                yes

SMBus Block Read                 no

SMBus Block Process Call         no

SMBus PEC                        yes

I2C Block Write                  yes

I2C Block Read                   yes

-----

Based from it, I could tell that SMBus Process Call is not supported.

could anyone suggests an alternative or give directions on how to make a process call?

Thanks in advance!

Francis

[Graham]

Francis:

Referring to:

https://www.kernel.org/doc/Documentation/i2c/smbus-protocol

SMBus Process Call:
===================

This command selects a device register (through the Comm byte), sends
16 bits of data to it, and reads 16 bits of data in return.

So, write 16 bits to a specific register, followed by a 16 bit read.

It seems you could synthesize this by using a "SMBus Write Word" followed by a "SMBus Read Word"

Or synthesize it out of single byte primitives, or ... .

You just need to make sure that if you stack up multiple commands to do the same thing, that in a multi-threaded environment, that the OS does not let other threads share/grab the device in between your commands.

--- Graham

==

[William Hermans]

Well the reason why the functionality you mention is not supported should be obvious from your output above. Block read isn't supported either. Honestly though, I'm not even sure how the block process call functionality is even useful. What's the point of writing up to 31 bytes into ONE register, and reading it back again ?

As far as answering your question goes. Technically you can not duplicate this functionality. Realistically, you could attempt to use the standard I2C block read listed above, or just use i2c_smbus_read_byte_data(), and loop over the whole register set ? Again, I honestly do not get the point of such a "feature".