Hi Ben, On Tue, 13 Oct 2009 23:50:10 +0100, Ben Dooks wrote: > On Wed, Sep 30, 2009 at 10:22:44PM +0200, Jean Delvare wrote: > > I2C bus drivers don't have to support I2C_M_REV_DIR_ADDR. It is a > > deviation from the I2C specification, which only makes sense to > > implement when really needed. > > Probably the right thing to do, does anything actually use this > support? As far as I know, the only chip which uses this is the "Maven" which is found on some Matrox G450 graphics cards to handle the second head. As the i2c-matroxfb driver builds on top of i2c-algo-bit, i2c-algo-bit is the only driver which needs to implement I2C_M_REV_DIR_ADDR. I've left it in i2c-algo-pcf and i2c-s3c2410 for now because at least they properly declare the I2C_FUNC_PROTOCOL_MANGLING functionality, but this could be reconsidered. The other protocol mangling flags are in a similar situation. For example I2C_M_NOSTART is only used by the Intel i915 and Matrox Maven chips. Both use i2c-algo-but, but no less than 9 other I2C adapter drivers implement it! Most of these implementations have most probably never been tested, and I wouldn't be surprised if some don't work. I2C_M_IGNORE_NAK is only used by the msp3400 audio processing driver. But it is implemented by embedded I2C adapter drivers which probably will never see this chip: i2c-davinci, i2c-omap, i2c-s3c2410 and i2c-stu300. I2C_M_NO_RD_ACK is only used by the ks0127 video driver, and only i2c-algo-bit implements it. That one is correct. > > Signed-off-by: Jean Delvare <khali@xxxxxxxxxxxx> > > Cc: Ben Dooks <ben-linux@xxxxxxxxx> > > --- > > drivers/i2c/busses/i2c-iop3xx.c | 6 ------ > > drivers/i2c/busses/i2c-mv64xxx.c | 3 --- > > drivers/i2c/busses/i2c-powermac.c | 2 -- > > I assume that I should merge this in my -next tree? Probably, yes. For now I have this patch in my own -next tree, but as all drivers affected are embedded ones, it would fit better in yours. I leave it up to you to decide what to do with the i2c-s3c2410 driver. As I understand it, it doesn't need to implement I2C_M_REV_DIR_ADDR nor I2C_M_IGNORE_NAK nor I2C_M_NOSTART, so you could simplify the code a bit and stop defining I2C_FUNC_PROTOCOL_MANGLING. BTW, is your -next tree visible somewhere? It might be convenient for me to be able to check what it includes. -- Jean Delvare -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
