On 2018-03-19 19:48, Guenter Roeck wrote: > On Mon, Mar 19, 2018 at 05:47:05PM +0100, Peter Rosin wrote: >> I also wonder if NXP will ever release a chip with part-id 0 and >> die-revision 0? If not, an all zero struct i2c_device_identity >> could be used instead of manufacturer_id 0xffff and that would >> simplify the pca954x driver code a bit more. But I guess we can >> never know the answer to that question. And even if we did, the >> answer might change later. But it would be nice... >> > > That would be nice. You could ask at i2c.support@xxxxxxx, but I guess > it would always be somewhat risky since the standard doesn't restrict > its use, and some product manager at NXP might decide in the future > that a device ID of 0x00 would be "cool". No need to bother NXP, PCA9848 has already claimed 0-0-0. Sigh. But while I googled that I found old datasheets for the chips PCA9672 through PCA9675 which use a different layout for the three bytes in the device id. They have 8 manufacturer bits, 7 category bits, 6 bits of feature indication and then 3 bits of revision. The top category bits are zero so it is compatible for NXP chips. But since noone else has implemented this, it is probably safe, but still a little bit disturbing. I also found that NXP apparently uses the same part id (0x100) and die revision (0) for PCA9570 and PCA9670. That seems odd. Example old datasheet (2006): https://www.digchip.com/datasheets/download_datasheet.php?id=1098812&part-number=PCA9672 Cheers, Peter
