Re: [PATCH] i2c: Split I2C_M_NOSTART support out of I2C_FUNC_PROTOCOL_MANGLING

On Thu, May 03, 2012 at 08:36:17PM +0200, Jean Delvare wrote:

You must also update the description of I2C_FUNC_PROTOCOL_MANGLING to
no longer mention I2C_M_NOSTART.

For backwards ABI compatibility _PROTCOL_MANGING still has to imply
_NOSTART, though it's unclear if that should be documented here.  For
drivers it should for the most part flow naturally as I'd expect they'll
end up implementing one or more of the mangling flags anyway.  For
applications I guess it means that they should fall back to checking for
_PROTOCOL_MANGLING if _NOSTART isn't there.

quoted

+#define I2C_FUNC_NOSTART		0x10000000 /* I2C_M_NOSTART */

Sorry for nitpicking but wouldn't I2C_FUNC_GATHER be a better name?
NOSTART is an implementation detail now, the high level feature is the
ability to gather multiple messages into one.

I kept it this way mostly because it means that the capability flag has
the same name as the feature flag which seemed helpful from a usability
point of view.

There is also the fact you could in theory also implement gather support
in other ways (eg, using DMA) though at present there's no API level
support for this and the users do have to code this specific
implementation.