From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jean Delvare Subject: Re: 10-bit address support Date: Thu, 10 Nov 2011 17:33:00 +0100 Message-ID: <20111110173300.3f75d2db@endymion.delvare> References: <20111110160739.540cda37@endymion.delvare> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: "Jeffrey (Sheng-Hui) Chu" Cc: Linux I2C List-Id: linux-i2c@vger.kernel.org On Thu, 10 Nov 2011 07:58:35 -0800, Jeffrey (Sheng-Hui) Chu wrote: > > > > -----Original Message----- > > From: Jean Delvare [mailto:khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org] > > Sent: Thursday, November 10, 2011 10:08 AM > > To: Linux I2C > > Cc: Jeffrey (Sheng-Hui) Chu > > Subject: 10-bit address support > > > > Hi all, > > > > After Sheng-Hui's fix to i2c-algo-bit, it would seem that we are almost > > there with 10-bit slave address support. There's one remaining thing > > that worries me though: the 7-bit and 10-bit address spaces overlap. > > From Documentation/i2c/ten-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)." > > From my understanding of the spec, there is no overlap. > The 10-bit client at 0x10 will be addressed by the following address sequence: > 0Xf0 0X10 or 0xf0 0x10 0xf1 > > The 7-bit client at 0x10 will be addressed by the following address sequence: > 0x20 or 0x21 > > 0xf0 is equivalent to 7-bit address of 0x78 which is a reserved address in 7-bit space. A compliant 7-bit client should not use or respond to this address. what you wrote above is completely exact, but is also completely unrelated to what I explained. The overlapping that currently exists is in the device names inside the kernel. It's a pure software issue. > Don't need to do any workaround. IMHO I'm certain we do. -- Jean Delvare