Re: [RFC PATCH] i2c: Support Smbus 3.0 block sizes up to 255 bytes.

[Wolfram Sang <wsa@kernel.org>]

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Hi Daniel,

wow, that was fast! Thanks for the prototype.

>  * I suggest to just settle on '3' for new macro and type names
>    (I2C_SMBUS3_*, i2c_smbus3_*)

Yes, I agree.

> 
>  * Block size definitions maintain I2C_SMBUS_BLOCK_MAX (32). Only adds
>    I2C_SMBUS3_BLOCK_MAX (255)
> 
>    - Means that drivers in drivers/i2c/busses/ default to their safe
>      32B block limit without refactoring.

This is totally fine for this patch. However, I still think I will do
the renaming to I2C_SMBUS2_BLOCK_MAX in kernel space later. Just so
people will understand by looking at the code that this is an old limit
which can be removed if there is interest.

> -	__u8 block[I2C_SMBUS_BLOCK_MAX + 2]; /* block[0] is used for length */
> +	__u8 block[I2C_SMBUS3_BLOCK_MAX + 2]; /* block[0] is used for length */
>  			       /* and one more for user-space compatibility */

I thought about this, too, and wondered if this isn't a size regression
in userspace with every i2c_smbus_data getting 8 times the size? But
maybe it is worth if backwards compatibility is maintained in an
otherwise not so intrusive manner? Jean, what do you think?

Happy hacking everyone,

   Wolfram


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